71-31,269 NELSON, Jr., Sigurd Oscar, 1937A SYSTEMATIC STUDY OF MICHIGAN CHELONETHIDA (ARACHNIDA), AND THE POPULATION STRUCTURE OF MICROBISIUM CONFUSUM HOFF IN A BEECHMAPLE WOODLOT. Michigan State University, Ph.D., 1971 Zoology University Microfilms, A XEROXC om pany, Ann Arbor, Michigan A SYSTEMATIC STUDY OP MICHIGAN CHELONETHIDA (ARACHNIDA) AND THE POPULATION STRUCTURE OP MICROBISIUM CONFUSUM HOPP IN A BEECH-MAPLE WOODLOT By Sigurd Oscar Nelson, Jr. A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Zoology 1971 PLEASE NOTE: Some Pages have indistinct print. F! tmed as received. UNIVERSITY MICROFILMS ABSTRACT A SYSTEMATIC STUDY OF MICHIGAN CHELONETHIDA (ARACHNIDA), AND THE POPULATION STRUCTURE OF MICROBISIUM CONFUSUM HOFF IN A BEECH-MAPLE WOODLOT By Sigurd Oscar Nelson, Jr. The systematics of Michigan Chelonethida (Pseudoscorpionida) and the population structure analysis of Microbisium confusum Hoff in a beech-maple woodlot are given. Twenty-nine species of pseudoscorpions are reported from Michigan, including two new species, Dinocheirus horricus and Parachelifer monroensis. and an undetermined species of Pseudogarypus. Disjunct distributions are discussed. Indirect evi­ dence of phoresy is presented. A key to Michigan pseudoscorpions, and an account of each species including data related to identification, dis­ tribution and habitat preference are included. Data concerning life stages, number of generations per year, and density are presented in the population analysis of M. confusum in beech-maple litter. The maxi­ mum density of all life stages reached 154.9 per square Sigurd Oscar Nelson, Jr. meter and dropped below 20, except for winter months , on a single occasion. were not found. discussed. All life stages overwintered. Males Parameters influencing the above are ACKNOWLEDGMENTS For generating my interest in invertebrates, and introducing me to the Chelonethida, I am indebted to my major professor, Dr. T. Wayne Porter. Not only has he helped me during this study, but his interest in students and enthusiasm for field work will serve as an inspiration to me throughout my entire professional career. I would like to thank the members of my committee: Dr. Roland L. Fischer for his assistance with systematic problems and for providing specimens deposited in the Michigan State University Entomology Museum; Dr. M. Max Hensley for his help related to distributional problems; and Dr. Ralph A. Pax for his critical analysis of the Tourney Woodland study. I am very grateful to Dr. William B. Muchmore of the University of Rochester for confirming specimens sent to him and for permitting me to examine slides and unmounted specimens from his private collection. My sincere thanks go to the many persons who have directly or indirectly aided in this study: Dr. Robert W. Husband of Adrian College for providing numerous pseudoscorpions for examination; Mr. Gary V. Manley for ii permitting me to examine materials in his personal col­ lection; Dr. Herman Slatis for his help regarding statis­ tical analyses; Dr. James Truchan of the Michigan Depart­ ment of Natural Resources for providing the photograph used in Figure 1; and to Mr. Wayne A. Yoder for his opinions regarding systematic and thesis problems. I wish to thank The Society of the Sigma Xi for a Grant-in-Aid of Research in 1968 to study pseudoscorpions. Mrs. Bernadette Henderson has my sincere thanks for providing materials necessary for this study. Finally, I am very grateful to my wife Sheila for her endless support during this study. She encouraged my efforts, actively participated in field work, and critically reviewed the manuscript. iii TABLE OF CONTENTS page PART I Introduction ..................................... 1 Literature Review 2 ............................... Collecting Methods ......................... . . 4 Preparation of Materials ......................... 6 Distribution ..................................... 9 Ecology and Habitat Preferences.............. 13 External Morphology........................... 27 Cephalothorax.............................. 27 Chelicerae................................. 29 Pedipalps ............................ 31 Legs........................................ 32 Abdomen.................................... 33 D e v e l o p m e n t ................................. 35 PART II SYSTEMATIC ACCOUNTS Key to Species of Michigan Pseudoscorpions. . . 37 Species Chthonius (Ephippiochthonius)tetrachelatus. . 44 Mundochthonius rossi ......................... 47 Apochthonius moestus . 50 . iv . . . . . . . page Microbisium b r u n n e u m .......................... 51 Microbisium c o n f u s u m .......................... 53 Syarinus enhuycki ............................. 62 Larca granulata................................ 63 Pseudogarypus s p ............................... 66 Apocheiridium stannardi ...................... 70 Lamprochernes oblongus 71 Lamprochernes minor ...................... .......................... 76 Parachernes squarrosus ...................... 77 Pselaphochernes parvus ...................... 79 Dendrochernes morosus ...................... 83 Acuminochernes tacitus ...................... 86 Acuminochernes crassopalpus................... 89 Mirochernes dentatus .......................... 92 Dinocheirus horricus .......................... 94 Dinocheirus pallidus .......................... 105 Illlnichernes distinctus...................... 110 Hesperochernes tamiae.......................... Ill Hesperochernes ewingi.......................... 113 Hesperochernes lymphatus...................... 117 Hesperochernes amoenus ...................... 119 Dactylochelifer coplosus...................... 120 Chelifer cancroides 124 .......................... Parachelifer m o n r o e n s i s ...................... v 128 page Idiochelifer nigripalpus ....................... 136 Palsochelifer callus 139 .......................... PART III POPULATION STRUCTURE OF MICROBISIUM CONFUSUM HOFF IN A BEECH-MAPLE WOODLOT Introduction ....................................... 169 Methods and Materials ............................. 171 Results and Discussion............................. 172 SUMMARY............................................. 179 A P P E N D I X .......................................... 181 LITERATURE CITED.................................... 182 Vi LIST OF TABLES TABLE page 1. Species habitat associations ................ 15 2. Pseudoscorpions found under the bark of dead t r e e s ................................... 17 3. Pseudoscorpions present in tree hollows 18 4. Pseudoscorpions found in nests of insects , birds and mammals............................. 20 5. Winter collections 24 6. More them one species from thesame habitat . 25 7. The life stages and number per square meter of Microbisium confusum in Tourney Woodland during the period 5 January 1969 to 3 January 1970 vii • 173 LIST OF FIGURES FIGURE page 1. Aerial net traps erected to capture flying i n s e c t s ...........................................22 2. Nest box of the wood duck, Aix sponsa, surrounded by ice. .......................... 22 3. Generalized body form of a chernetid pseu­ doscorpion ....................................... 28 4. Palp of a female Pselaphochernes parvus Hoff, lateral v i e w .................................... 30 5. Generalized chernetid chelicera, lateral v i e w .............................................. 30 6. Palpal chela of Microbisium confusum Hoff, showing trichobothria,adult female. . . . 57 Palpal chela of M. confusum, showing tri­ chobothria, deutonymph I T. . . . . . 57 7. 8. Palpal chela of M. confusum, showing tri­ chobothria, protonymph T ..................... 57 9. Genital region of M. confusum, male. . . . 60 10. Genital region of M. confusum, female . . . 60 11. Chthonius (Ephlpplochthonius) tetrachelatus (Preyssler), female, first leg ............. 142 12. C. (E.) tetrachelatus, female, lateral view of cKela..........................................142 13. C. 14. C. (E.) tetrachelatus, female, feathered coxaT spines I I 7 ......................... 142 15. C . (E.) tetrachelatus, female, coxal area with feathered coxalspines and inter-coxal tubercle......................................... 142 (E.) tetrachelatus, female, fourth leg. viii . 142 page 16. C. (E.) -tetrachelatus, female, dorsal view of p a l p ......................................... 142 17. Mundochthonius rossi Hoff, female, lateral view of chela ................... • • • . 144 18. M. rossi, female, second coxae with combTike coxal spines................................144 19. M. rossi, female, comb-like coxal spines . . 144 20. M. rossi, female, dorsal view of palp . . 144 21. Apochthonius moestus (Banks) , female, first coxae with s p i n e s . ............................ 144 22. A. moestus, female, coxal s p i n e ............144 23. A. moestus, female, lateral view of chela. 24. A. moestus, male, dorsal view of palp . 25. . . 144 • . 144 Microbisium brunneum (Hagen), female, lateral view of c h e l a ............................ 26. M. brunneum, female, dorsal view of palp . 27. Microbisium confusum Hoff, female, first leg I I ................... 146 . 146 146 28. M. confusum, female, fourth l e g ............ 146 29. M. confusum, female, movable finger of chelicera with sclerotized knob...................... 146 30. M. confusum, female, dorsal view of palp . . 146 31. M. confusum, female, lateral view of chela . 146 32. 33. Syarinus enhuycki Muchmore, female, movable finger of c h e l i c e r a ............................ 148 S. enhuycki, male, movable finger of cheli­ cera 148 34. £3.enhuycki, male, lateral view of chela . . 148 35. S. enhuycki, female, dorsal view of palp . . 148 ix page 36. 37. Larca granulata (Banks) , male, lateral view of chela . 1 . . . . . . . . . . L . granulata, male, movable finger of c h e l l c e r a . ........................... 148 148 38. L . granulata, male, dorsal view of palp. . 148 39. Pseudogarypus sp., male, lateral view of chela . . 7............................... 150 Pseudogarypus sp., male, dorsal view of palp . .7 ............................... 150 40. 41. 42. Pseudogarypus sp., male, carapace with eye pattern 7 ........................ 150 Apocheiridium stannardi Hoff, female, first Teg: : : r“ :r- ............. . . . . 150 43. A. stannardi,female, fourth leg 44. A. stannardi,male, dorsal view of palp. 45. A. stannardi,male, palpal seta . . . . 150 46. A. stannardi,male, lateral view of chela • 150 47. Lamprochernes oblongus (Say), female, lateral view oi chela. ................ 48. L. oblongus, female, dorsal view 49. L. oblongus. female, first leg...... 50. L. oblongus, female, fourth leg 51. 52. 53. 150 . of palp 150 152 • 152 . . . . 152 Lamprochernes minor Hoff, female, dorsal view of p a l p ........................ L. minor, female, lateral view of chela. 152 . Parachernes sguarrosus Hoff, female, lateral view of c h e l a . ............... 152 154 54. P. sguarrosus. female, dorsal view of palp. 55. Pselaphochernes parvus Hoff, female, dorsal view of p a l p ........................ 154 x 152 154 page 56. P. parvus, female, fourth tarsus . . . . 154 57. Dendrochernes morosus (Banks), female, dorsal view of p a l p ....................... 154 58. D. morosus, female, lateral view of chela . 154 59. Acuminochernes tacitus Hoff, male, lateral view of c h e l a ............................. 156 60. A. tacitus, male, dorsal view of palp 61. Acuminochernes crassopalpus (Hoff), male, dorsal view-of p a l p ................ 156 A. crassopalpus, male, lateral view of cheTa I . . ............................. 156 Mirochernes dentatus (Banks), male, lateral view ol: c h e l a ............................. 156 62. 63. . . 156 64. M. dentatus, female, lateral view of chela. 156 65. M. dentatus, female, dorsal view of palp • 156 Dinocheirus horricus, new species, male, dorsal view of p a l p ....................... 158 66. 67. D. horricus, male, lateral view of chela . 68. D. horricus, male, cheliceral galea . . . 158 69. Dinocheirus pallidus (Banks), male, lateral view of c h e l a ............................. 158 70. D. pallidus, male, dorsal view of palp . 158 . 71. Illinlchernes distinctus Hoff, male, lateral view of c h e l a . ................... . 158 160 72. I_. distinctus, male, dorsal view of palp 73. I_. distinctus, male, palpal seta . . . . 74. I_. distinctus, male, palpal seta . . 160 75. Hesperochernes tamiae Beier, female, dorsal view o£ p a l p ............................. 160 xi . . . 160 160 page 76. H. tamiae, female, lateral view of chela . 77. Hesperochernes ewingi (Hoff), male, lateral view of chela..................... 160 78. H. e w ingi, male, dorsal view of palp. . 160 79. Hesperochernes lymphatus (Hoff), female, lateral view of c h e l a .................... 162 . 80. H. lymphatus, female, dorsal view of palp 81. Hesperochernes amoenus Hoff, male, dorsal view of p a l p . ............................ 162 82. H. amoenus, female, lateral view of chela . 83. Dactylochelifer copiosus Hoff, female, dorsal view of palp ........................ 162 84. D . copiosus, female, lateral view of chela. 85. Chelifer cancroides (Linnaeus), female, lateral view of chela ......................164 female, dorsal . 160 162 162 164 86. C. cancroides, 87. C. cancroides, female, tergal halves. . . 164 88. C. cancroides, claw . . 164 89. Parachelifer monroensis, new species, female, tergites 7-9 I .................. 166 90. P. monroensis, female, dorsal view of palp. female, tarsal view of palp. . 164 166 91. P. monroensis, female, lateral view of cheTa I I 7 ............................ 166 92. Idiochelifer nigripalpus (Ewing) , male, lateral view of c h e l a . ...................168 93. 1^. nigripalpus, male, dorsal view of palp . 16 8 94. nigripalpus, male, fourth coxa with anterolateral spur ......................... 168 95. I. nigripalpus, male, tibia and tarsus of Tourth leg .............................. 16 8 xii page 96. T. n i g r i p a l p u s, male, -tergal halves . . . 97. Paisochelifer callus (Hoff), female, dorsal view of p a l p . .................................. 168 98. c a l l u s , female, tibia and tarsus of Fourth l e g ........................... . 99 . . 101. 100 168 . 168 M i c r o b isium confusum Hoff, protonymph density I ......................................175 M. c o n f u s u m , deutonymph density . . . . M. c o n f u s u m , adult female density. xiii . . 175 . 175 LIST OF MAPS MAP 1. page Distribution of Chthonius (Ephippiochthonius) tetrachelatus .................................. 46 2. Distribution of Mundochthonius rossi . . . . 49 3. Distribution of Apochthonius moestus . . . . 52 4. Distribution of Microbisium brunneum . . . . 54 5. Distribution of Microbisium confusum . . . . 61 6. Distribution of Syarinus enhuycki ............ 64 7. Distribution of Larca granulata ............... 67 8. Distribution of Pseudogarypus sp................... 69 9. Distribution of Apocheiridium stannardi . . . 72 10. Distribution of Lamprochernes oblongus. . . . 75 11. Distribution of Lamprochernes minor................78 12. Distribution of Parachernes sguarrosus. . . . 80 13. Distribution of Pselaphochernes parvus. . . . 82 14. Distribution of Dendrochernes morosus . . . . 85 15. Distribution of Acuminochernes tacitus. 88 16. Distribution of Acuminochernes crassopalpus . 17. Distribution of Mirochernes dentatus . . . . 93 18. Distribution of Dinocheirus horricus . . . . 106 19. Distribution of Dinocheirus pallidus . . . . 109 20. Distribution of Illinichernes distinctus . xiv . . . . • . 91 112 page 21. Distribution of Hesperochernes tamiae . 114 22. Di stribution of Hesperochernes ewingi . 116 23. Di stribution of Hesperochernes lymphatus . 118 24. Distribution of Hesperochernes amoenus. 121 25. Distribution of Dactylochelifer copiosus . 123 26. Distribution of Chelifer cancroides. 127 27. Distribution of Parachelifer monroensis 135 28. Distribution of Idiochelifer nigripalpus . 138 29. Distribution of Paisochelifer callus 140 30. Michigan map with county names xv ............ 181 LIST OP APPENDICES page Michigan map with county n a m e s .................. xvi 181 PART INTRODUCTION Pseudoscorpions are small arachnids less than eight millimeters long. They superficially resemble true scor­ pions except for the absence of a postabdomen and accompany­ ing sting. These animals are diverse in their habits, and often occur in large numbers, but due to their small size and secretive behavior they usually go unobserved. More than 2,000 species of pseudoscorpions have been described placing them among the major orders of Arachnida in number of species. Only spiders, mites, and harvestmen have greater numbers of species. Yet little is known about the biology of this group. Due to the general lack of knowledge concerning pseu­ doscorpions a twofold study was initiated. The objective of the first study was to advance the knowledge of pseu­ doscorpion systematics by the presentation of keys and descriptions along with the ecology and distribution of Michigan species. The object of the second study was to determine the population structure of Microbisium confusum Hoff and some of the parameters influencing this species in a beech-maple litter situation. 1 LITERATURE REVIEW The recorded history of pseudoscorpions is dated to Aristotle's De Animalibus Historiae, while the systematic history of pseudoscorpions began with the recognition of two species by Linnaeus in the tenth edition of Systema Naturae, 1758. The order Faux Scorpiones (Pseudoscor- piones) was first used by Latreille (1806-9) and included pseudoscorpions and solpugids. the ordinal name Chelonethi. In 1876 Thorell proposed Today the ordinal name Chelonethida is widely accepted in America while Pseudoscorpionidea is preferred in Europe. While earlier works were of a classificatory nature along with species descriptions, major efforts were initiated in both the United States and Europe in the early 1930's by J. C. Chamberlin and M. Beier, respec­ tively. Morphological monographs on pseudoscorpions have been written by Kaestner (1927) , Chamberlin (1931), Beier (1931-1941), Roewer (1940) and Vachon (1949). Beier, during the years 1958-1967, published extensive keys for various parts of the world, and Hoff (1958) published a key to North American genera. 2 3 The syst.emat.ics of North American pseudoscorpions has been extensively advanced by Chamberlin especially during the 1930's, Hoff (1944-64) and Muchmore during the past decade. In Michigan preliminary studies of pseudoscorpions were made by Fenstermacher (1959) and Manley (1969). While the aforementioned works were of a morphological and systematic nature, Weygoldt (1969) published The Biology of Pseudoscorpions, a 145-page comprehensive volume with emphasis on reproduction and development. Recent papers related to life history analyses and quan­ titative sampling by Gabbutt have contributed to the popu­ lation ecology of pseudoscorpions. COLLECTING METHODS Many pseudoscorpions, especially larger species, were collected by hand picking from under bark, boards, or by sifting rotten wood. Occasionally this method yielded a large number of individuals. However, due to the secretive nature and small size of the animals, many individuals were probably overlooked. Samples of leaf litter, soil, bark, small mammal and bird nesting materials, and woody debris were removed to the laboratory and placed in Tullgren funnels. Tullgren funnels consist of two main parts; a lower funnel and an upper reflector containing a low power (25-50W) light source. A one-eighth inch screen is placed in the lower funnel, atop which samples thought to contain pseudoscor­ pions are placed. The light source is placed above the sample thus creating a temperature-moisture gradient. As time passes the uppermost portion of the sample pro­ gressively becomes warmer and drier, thus driving most arthropods, including pseudoscorpions, downward into a collecting jar. The drying time varies from a few hours to a few weeks dependent upon the moisture content and volume of the sample. The collecting jar usually 4 5 contains ethyl alcohol, however, during this study ethylene glycol was used. Ethyl alcohol is more volatile than ethylene glycol and its use may cause flames to enter the funnel, thus hampering the extraction of many arthro­ pod s . The surface tension of ethylene glycol is suffi­ ciently low to entrap specimens. As ethylene glycol is not a preservative the extracted arthropods should be transferred to 70 per cent ethyl alcohol. Field collections were placed in large plastic bags along with date locality information. Those samples not immediately placed in Tullgren funnels were stored in a cold room maintained at approximately 45°F. All samples were allowed to reach room temperature before being placed in the funnels. Sample materials were removed from the plastic bags and those substances too large to be placed in the funnels were broken down. Materials were loosely placed in the funnels in such a manner that a slope to an open central region was created, thus facilitating movement of the arthropods downward into the collecting jar. The col­ lecting jars were examined for pseudoscorpions. Pseu­ doscorpions were removed from the collecting jars, placed in vials containing 70 per cent ethyl alcohol along with proper date locality information, and stored until a critical examination was made. Specimens were also obtained by examining collections made previously by other individuals. PREPARATION OF MATERIAL The examination of most pseudoscorpion species requires proper orientation and magnification of materials. It is imperative that specimens be prepared as indicated by Hoff (1949), as outlined below. Pseudoscorpions were individually placed in a Syra­ cuse watch glass containing 70 per cent alcohol. The chelicerae and pedipalps were removed from the body along with one of the first and fourth walking legs at the coxal-trochanteral joint. The chela was separated from the tibia of one pedipalp and the palpal fingers were spread apart. The above appendages were placed in beech- wood creosote for clearing. After piercing the abdominal pleural wall the body was placed in a test tube containing 10 per cent KOH. The test tube was heated in a boiling water bath until internal materials were dissolved. Care was taken to avoid overtreatment in the KOH solution. When overtreated, bleaching and discoloration resulted. The body was transferred from KOH to distilled water and allowed to stand for approximately 24 hours. By gently creating a pumping action on the abdomen with a small needle, excess visceral material was removed. 6 Next, 7 the body was placed in a 1/50 N HC1 solution, neutralizing any remaining KOH. After the above treatment the body was transferred tothe beechwood creosote vial containing the appendages and allowed to clear overnight. All specimens were mounted directly from beechwood creosote to Canada balsam. Microscope slides, after cleaning, were divided into approximately three equal parts. The first part was reserved for the slide label while the remaining two-thirds of the slide was used for mounting the specimen. The body and palps were placed under one coverslip which was supported by two finely drawn glass rods. Occasionally smaller specimens did not require support. The body was mounted ventral side up while the palp with the chela attached was mounted dorsal side up. The chela, previously removed from the other palp, was mounted lateral side up. The chelicerae and legs were placed under a second coverslip without supporting rods, thus compressing the legs for measuring purposes. Slides were labeled with the proper date locality information and placed in a drying oven. Specimens were identified through the use of numerous publications, the majority of which were authored by C. Clayton Hoff. The prepared slides were examined with a compound microscope at powers of 100 and 430X. An ocular micro­ meter was used to measure important body parts. Standard 8 measurements, illustrated by Chamberlin (1931), were used. All absolute measurements are given in millimeters. DISTFIBUTION Pseudcscorpions as an Order are cosmopolitan in dis­ tribution. They reach their greatest densities and diversity in the tropics and subtropics, yet many are present in the temperate regions. Many families are cosmopolitan in distribution while others may be more localized. polar. Still others are circumtropical or circum- The genus Neobisium is circumpolar in dis­ tribution, with N. muscorum Leach occurring as far north as northern Scandinavia, and N. jugorum (L. Koch) occurring as high as 2900 meters in the Alps. The species Chelifer cancroides (Linnaeus) and Cheiridium museorum (Leach) are cosmopolitan. The dispersal of pseudoscorpions resulting in such widespread distribution is of considerable interest. As terrestrial arthropods lacking a flight mechanism, their ability to disperse would appear limited. tive dispersal mechanisms do exist. However, effec­ Vachon (1940, 194 7a, 1947b) reported large numbers of pseudoscorpions attached to insects and birds. This use of one species by another species for transportation is called phoresy. Vachon believed phoretic behavior to be prevalent among adult 9 10 females and Gabbutt (1970) felt that dispersal may be facilitated by adult longevity. as carriers. Mammals may also serve Indeed, man, although not necessarily in a literal phoretic sense, may be responsible for the wide­ spread distribution of many species, especially those species that are associated with domestic situations (buildings) such as Chelifer cancroides. Chamberlin (1938) reported many species of pseudoscorpions taken at coastal quarantine stations from incoming merchandise. Finally, air currents may be responsible for the wide­ spread distribution of many species, especially smaller pseudoscorpions. Of the pseudoscorpions found in Michigan only Chelifer cancroides is found throughout the United States. Only one other species, Microbisium confusum Hoff is found west of the Continental Divide. Many Michigan species are widely distributed east of the Rocky Mountains. M. confusum and Lamprochernes oblongus (Say) are distributed from the eastern States as far west as Colorado. Apochthonius moestus (Banks) is widely distributed throughout the eastern and southcentral States as far west as New Mexico. Chthonius tetrache1atus (Preyssler) is an eastern species that also occurs in Europe. ares Eastern and central species Microbisium brunneum (Hagen) , Larca granulata (Banks) , Illinichernes distinctus Hoff, Dinocheirus pallidus (Banks), Mirochemes dentatus (Banks), and Paisochelifer callus 11 (Hoff). Syarinus enhuycki Muchmore and Hesperochernes tamiae Beier occur in the northeast, while Mundochthonius rossl Hoff and Lamprochemes minor Hoff occur in the Northcentral States. Species that occur in the Midcentral States include: Parachernes squarrosus Hoff, Psela- phochernes parvus Hoff, Hesperochernes ewingi (Hoff), H. lymphatus (Hoff), Acuminochernes crassopalpus (Hoff), and Idiochelifer nigripalpus (Ewing). Still other species show disjunct distributions Apocheiridium stannardi Hoff is found in Michigan, Illinois, and Colorado, while Acu­ minochernes tacitus Hoff is only found in Michigan and Colorado, and Hesperochernes amoenus Hoff is only found in Michigan and South Dakota. Disjunct populations could result from a number of factors. First, they could be actual relict populations. Relict populations are those populations that originally encompassed a much larger area, but due to habitat changes isolated or disjunct pockets of the species occur. Secondly, dispersal resulting from phoretic behavior or by man could result in disjunct populations. Thirdly, in groups of species lacking in-depth systematics and distributional studies disjunct records occur. Finally, disjunct populations could artificially occur based on misidentification of species. Within Michigan many species are widespread, while others when adequate records are present, show definite 12 geographic patterns. Species occurring in both the Upper and Lower Peninsula are: Mundochthonius rossi, Microbisium brunneum, M. confusum, Apocheiridium stannardi, Dinochelrus pallidus, Acuminochernes tacitus, Dendrochernes morosus (Banks), and Chelifer cancroides. Only two species, Pseudogarypus sp. and Hesperochernes amoenus, occur exclusively in the Upper Peninsula, although Mun­ dochthonius rossi, taken from five western counties in the Upper Peninsula, is represented in the Lower Penin­ sula by a single specimen from Ingham County. Larca granulata, Lamprochernes oblpngus, L. minor, Pselaphochernes parvus, Mirochernes dentatus, Dinocheirus horricus n. sp., and Dactylochelifer copiosus Hoff are generally widespread in the Lower Peninsula. Species found only in the southern one-half of the Lower Peninsula are: Chthonius tetrachela- tus, Hesperochernes lymphatus, H. ewingi, Acuminochernes crassopalpus, and Idiochelifer nigripalpus■ The following species have been collected too infrequently to establish any distributional patterns: Syarinusenhuycki, Para- chernes squarrosus, Hesperochernes tamiae, and Paisochellfer callus. To this list of infrequent records must be added three species taken only from those counties adjacent to Indiana and Ohio: Apochthonius moeatus, Illinichernes distinctus, and Parachelifer monroensis n. sp. ECOLOGY AND HABITAT PREFERENCES Pseudoscorpions are reported from a wide variety of habitats, often occurring in large numbers. Physical factors essential for the well-being of most species are adequate crevices enabling the pseudoscorpions to retreat, areas of optimum relative humidity, and favorable temper­ atures. Weygoldt (1969) reported Neobisium muscorum only reproduces in captivity at temperatures approximately 15 to 18°C. Other factors, yet unknown to researchers, may be of considerable importance. Only a few quantitative studies of pseudoscorpions have been undertaken. Their small $ize and secretive behavior probably discourages many investigators. Usually, if numbers of individuals are reported, they represent a single sample and are not indicative of the population structure within a given locality. Still, these numbers are of importance and often reach con­ siderable magnitude. For example, forty-seven individ­ uals of Microbisium confusum were extracted from 10 square cm. of pine litter of an unknown depth; fifty-five individuals of Idiochelifer nigripalpus were hand-picked from the bark of black cherry. 13 These numbers, however, 14 are of little value in determining population structure. Only random quantitative sampling over a period of time will supply information concerning the population dynamics of a species. Gabbutt (1967) found total numbers of Chthonius ischnocheles (Hermann) in Oxon, England to range from 128.5 to 619.7 individuals per square meter over a two-year period, excluding winter months. Many species of pseudoscorpions live in leaf litter and soil, under the bark of trees, in tree hollows, under stones, and within rock crevices. Still other species are found in the nests of mammals, birds, and insects. Other species are associated with domestic situations and are found in buildings such as barns, greenhouses, and private homes. Of more recent interest are the cavernicolous species, chiefly Chthonidae and Neobisiidae. A number of species inhabit the seashore. Weygoldt (1969) reported a zonation of four different species of pseudoscorpions from the high-tide line to the sand dune area along the coast of North Carolina. Neobisium maritimum (Leach), a European species, occupies an inter­ tidal zone and is submerged twice daily. The habitat associations of pseudoscorpions collected in Michigan are shown in Table 1. Some of the more common associations are discussed below. Nine species of pseudoscorpions were taken from lit­ ter and soil, with the Heterosphyronida and Diplosphyronida 15 TABLE 1.--Species habitat associations. -hH« S # ■co s S' o .... M a )C o 4-J 4 J JJ S HETEROSPHYRONIDA Chthonlun tetrachelatus Apoohtnonlua moaatua MundocntnonTua roaal DIPLOSPHYRONIDA Microbiaium brunneum Micropiaiuw contuaum syarinua enhuyckl Larca granulata MONOSPHVRONIDA Paeudogarypua ap. Apocne trialuw atannardi Lanqprocharnea obiongua Lamprocharnaa minor paracnarnaa aquarroaua raalaphocharnaa parvua oandrocharnaa moroaua Haaperocharnea awinaT haapa roche m a n lymphatua haaparocnarnaa amoanua Haaparochornea tarniaa ' iiilnicharnaa diaimotua Hlrocharnaa dantatua Dlnoohelroa pallldua blnochalrua norrlcua Acuminochernea tacTEua A. eraaaopalpaa Chernatinaa nympha Chelifer cancroidaa fraiaochellTer eallua Idiochallfar nlgrlpalou Parachaiifer monrocnaia Dactylochallfar copio aua Chailfarldaa nympha § 3O .G 4 1 ii 5 U s . 1e « *2 « i .* s s » ) 9e CS « jS a > m pi .q5 e a to x > in o => a C 4 k < Bo -> H > « « a >0 > J3 u jT3 T3 t< >(a 1 J3 IB C O . O “d . O 25 2 - H B ^ w -iH J o t«o 4i «l iQ 3 4IbB) M 2 g § 3 h -c H i™t t r H§ 4(J o - O M O 1) 0 *bj a n O P J 5 H Pa eh x o UM 4 • rt ata 4 , O3i g 9 3H ma ■SS le ■a •4 <4l« o c 3 3 C. tetrachelatus M. brunneum M. confusum 1 Pseudogarypus sp. 1 A. stannardi L. oblongus P. squarrosus 1 1 1 1 1 1 P. parvus D . morosus 1 H. ewingi 1 H. lymphatus M. dentatus Chernetinae nymphs I. nigripalpus H ■vj 0c +J 0 ap0 ) • 0 c0 o& to • 0p 0 c < •Po 00 1 mp 0 ca p0 0 O 0 3V 0 0 3 & ■H &.0pO’ ■IPop o 0.U culu I a 3 ic 0 ■Q0 0 U a ■P a a I vlrginiana TABLE 3.— Pseudoscorpions present in tree hollows. i •H to a Ga 0 0 U 0 oa o 0 p P O'H o 0 1 o u Mundochthonius rossi 0 0 fa 0c G 0 C 0 0 a to 0 0 ft 3 G 0 -r4 0 § X c 0 G M 0 fa > D 0 r4 a 0 e G 0 Ji H 0 0 P 4i 0 hi 0 P o 0 H a 0 e M 0 O’ •P < 1(0 2 1 Microbisium confusum Larca granulata Pseudogarypus sp. t rH > 3 1 1 1 1 1 oa 1 Apocheiridium stannardi Pselaphochernes parvus Illinichernes distinctus 1 lm Mirochernes dentatus Dinocheirus pallidus Acuminochernes tacitus A. crassopalpus Chernetinae nymphs ^insect nests mmammal nests 1 li 1 lm 2 1 li 1 2 1 1-lm 2 1 lm 1 1 lm 1 3 1-lm lm lm lm 19 shown between a pseudoscorpion and any tree species. Srgar maple was the most common tree with hollows containing pseudoscorpions. Often the tree hollows contained the remains of mammal, bird, and insect nests (Table 4), or less fre­ quently the active nests of a small mammal or bumble bees. These nests often contained a rich supply of food. doscorpions feed on small arthropods. Pseu­ The presence of a pseudoscorpion within the nest may have been the result of phoresy. The only direct record of possible phoresy was reported by Fenstermacher (1959) . He reported Lamprochernes oblon­ gus from under the elytra of the elaterid beetle, Alaus oculatus (Linnaeus). does exist. However, indirect evidence of phoresy Such evidence points to phoresy even though the pseudoscorpion is not collected attached to a carrier. Female Hesperochernes ewingi, H. lymphatus and Dinocheirus pallidus were collected, on separate dates, in aerial net traps (Fig. 1) erected to capture flying insects. There is a possibility that the pseudoscorpions entered the traps via air currents and were not attached to a carrier at any time. Apocheiridium stannardi and Lamprochernes oblongus were collected from nest boxes of the wood duck, Aix sponsa (Linnaeus). The boxes, attached to dead trees in a flooded area, were completely surrounded by ice when collected (Fig. 2), but during more seasonal periods would TABLE 4.— Pseudoscorpions found in nests of insects, birds and mammals. s * ■p a 0 C ® a 3 0 s a a 3 P 0 P 0 -H s u o ■p « o P 3 •PHxc r-H TJ W H n 3 3 0 ■aP 3I O a ■0Q a a3 3 a >a 3 H 3 E 0 E ® a TJ ■HI 0 C Chthonius tetrachelatus Microbisium confusum Larca granulate Apocheiridium stannardi Lamprochernes minor Lamprochernes oblongus Illinichemes distinctus la 1 1 1 1-la lb Hesperochernes ewingi Mirochernes dentatus Dinocheirus pallidus Acuminochernes tacitus 1 A. crassopalpus Chernetinae nymphs lb Chelifer cancroides Cheliferidae nymphs a, b, and c indicate the same nest lc lc 1 1 21 Fig. 1 Aerial net traps erected to capture flying insects. Fig. 2 Nest box of the wood duck, Aix sponsa, surrounded by ice. rtf'*" 22 Figure 2 23 be surrounded by water. However, man may have introduced nesting materials containing pseudoscorpions, therefore, phoresy would not have occurred. A male Dactylochellfer copiosus was collected, atop an automobile hood, at a black light. insects. The black light was used to attract flying Finally, a female Hesperochernes tamiae was collected in a pit trap, and may have entered phoretically. Weygoldt (1969) reported that many species, including several Chthonius species, and some Chernetidae and Cheliferidae, construct silken chambers in order to hibernate. He indicated that the pseudoscorpions resisted extraction by Tullgren funnel methods. During winter months, November through March, sixteen species of pseudoscorpions were collected in addition to unidentified chernetine and cheliferid nymphs (Table 5). All of the above species, with the exception of the cheliferid nymph, were extracted using a Tullgren funnel. Sixteen samples yielded more than one species of pseudoscorpion (Table 6). were present. In four samples, three species Microbisium confusum and Dinocheirus pal- lidus occurred most frequently with other species although these two species were never collected together. of these samples were taken from tree hollows. Eight It is not the intent of the writer to imply that any of the samples were homogeneous in nature. However, Hoff (1959) stated that inter-species associations are probably the result of TABLE 5.— Winter collections. Species Apochthonius moestus Mundochthoniui~~ross i Microbisium brunneum Microbisium confusum Larca cjranulata Apocheiridium stannardi Lamprochernes oblongus"Acuminochernes crassopalpus Dinocheirus pallihus Dinocheirus norricus Mirochernes dentatus Hesperochernes ewingi Hesperochernes lymphatus Hesperochernes amoenus Chernetinae nymphs Chelifer cancroides Dactylochelifer copiosus Cheliferidae nymphs Months March November December November, December January, February December February February March February, March January February, March February February November March November, January, February November, December, March February Adults X X X X Nymphs X X X X X X X X X X X X X X ? X X X X X X 25 TABLE 6.— More than one species from the same sample. Locality Habitat Species Baraga Co. T49N t R33WI 819 Hollow at the base of a live sugar maple Mundochthonius rossi Microbisium confusum Genesee Co. T 9Ni R 7Ei S 2 Old honey bee nest and wasp nest in hollow of a largetooth aspen Dinocheirus pallidus Acuminochernes erassopalpus Gogebic Co. T48N: R45H: S36 Leaf litter Mundochthonius rossi Microbisium confusum Grand Traverse Co. T26N: RIOWt S31 Old straw in fallen barn Microbisium confusum Dinocheirus horrlcus Chelifer cancroidea Houghton Co. T51N > R35Wi S19 Hollow at the base of a dead sugar maple Mundochthonius rossi Microbisium confusum Huron C o . T16N: R 9Ei S12 Peromyscus leucopus neat in the hollow of a live red maple Mirochernss dentatus Dinocheirus pallidus Acuminochernes craesopalpus Ingham Co. T 4Ni R 1W: S30 Hollow in a live beech Dinocheirus pallidus Acuminochernes crassopalpus Ingham Co. Grain bin Lamprochernes minor Paiaochelifer callus Ingham Co. T 4N i R lWt S18 Inside an elm stump Chthonius tetrachelatus Microbisium brunneum Pselaphochernes parvus Kalamazoo Co. Ground nest of Bombus bimaculatus Chthonius tetrachelatus Chernetinae nymph Lake Co. T19Ni R13Wi S22 Rotten wood in hollow of a live white oak Mirochernaa dentatus Dinocheirus pallidus Lenawee Co, T «Si R 3E Beech-maple leaf litter Apochthonius moestus Microbisium confusum Marquette Co. T46NI R28Ht 815 Jack pine stump material Mundochthonius rossi Hesperochernes amoanus Oakland Co. T 7Ni Rl6Et Hollow at the base of a live red ash Microbisium confusum l. ) 28. T)ir-triV.ution of I d i o c h e l i f r r /i.i^ripalnur- 139 of black cherry and under bark of dead elm. CLINTON C O . : cited from Manley (1969). Paisochelifer callus (Hoff) Hysterochelifer callus Hoff, 1945a: 515. Paisochelifer callus, Hoff, 1946e: 487, 1949: 489, 1950: 10, 1958: 33; Fenstermacher, 1959: 25; Manley, 1969: 9. This species is known from Michigan on the basis of a single male, initially reported by Fenstermacher (1959) , and subsequently by Manley (1969). Diagnostic characters are given in the key and illustrated in Figures 97, 98. Measurements of Fenstermacher's specimen agree with Hoff (1945a) with the exception of a slightly wider chelal hand. Measurements include: body length 2.12; palpal femur 0.62 long, 0.18 wide, length x width 3.42; tibia 0.56 long, 0.235 wide, length x width 2.38; chela without pedicel 1.07 long, 0.36 wide, length x width 2.97; chelal hand 0.5 long, 0.30 deep; movable finger 0.59 long. Distribution (Map 29), Habitat Preference and Record. This species occurs in the States of Illinois, Maryland, and Michigan. Fenstermacher's reference to Washington County, Arkansas as the type locality of P. callus was in error. The Michigan record is based on a single collection from CLINTON CO.: 24 Oct. 1956 by R. A. Scheibner of 1 female from a grain bin collected with Lamprochernes minor. 141 Figs. 11-16. Chthonius (Ephippiochthonius) tetra- . chelatus (Preyssler), female. First leg. 12. Lateral view of chela. 13. Fourth leg. spines. 11. 14. Feathered coxal 15. Coxal area with feathered coxal spines and inter-coxal tubercle. 16. Dorsal view of palp. X42 143 Figs. 17-20. Mundochthonius rossi Hoff, female. Lateral view of chela. 18. Second coxae with comb-like coxal spines. like coxal spines. 17. 19. Comb- 20. Dorsal view of palp. Figs. 21-24. Apochthonius moestus (Banks). Female. 24. Male. with spines. 21. First coxae 22. Coxal spine. Lateral view of chela. view of palp. 21-23. 23. 24. Dorsal 144 17 145 Figs. 25-26. Microbisium brunneum (Hagen), female. 25. Lateral view of chela. 26. Dorsal view of palp. Figs. 27-31. Microbisium confusum Hoff, female. First leg. 28. Fourth leg. 29. Movable finger of chelicera with sclerotized knob. 30. Dorsal view of palp. Lateral view of chela. 27. 31. 146 147 Figs. 32-35. Syarinus enhuycki Muchmore. Female. 33, 34. Male. fingers of chelicerae. of chela. Figs. 36-38. 32, 35. 32, 33. Movable 34. Lateral view 35. Dorsal view of palp. Larca granulata (Banks), male. Lateral view of chela. finger of chelicera. of palp. 36. 37. Movable 38. Dorsal view 148 38 36 37 32 149 Pigs. 39-41. Pseudogarypus sp., male. view of chela. 39. Lateral 40. Dorsal view of palp. 41. Carapace with eye pattern. Pigs. 42-46. Apocheiridium stannardi Hoff. Female. 44-46. Male. 43. Fourth leg. palp. 42. First leg. 44. Dorsal view of 45. Palpal seta. view of chela. 42, 43. 46. Lateral 150 151 Figs. 47-50. Lamprochernes oblongus (Say), female. 47. Lateral view of chela. view of palp. 48. Dorsal 49. First leg. 50. Fourth leg. Figs. 51-52. Lamprochernes minor Hoff, female. Dorsal view of palp. of chela. 51. 52. Lateral view 152 r VVvVA 49 153 Figs. 53-54. Parachernes sguarrosus Hoff, female. 53. Lateral view of chela. 54. Dorsal view of palp. Figs. 55-56. Pselaphochernes parvus Hoff, female. 55. Dorsal view of palp. 56. Fourth tarsus. Figs. 57-58. Dendrochernes morosus (Banks), female. 57. Dorsal view of palp. view of chela. 58. Lateral 154 55 56 155 Figs. 59-60. Acuminochemes tacitus Hoff, male. 59. Lateral view of chela. 60. Dorsal view of palp. Figs. 61-62. Acuminochemes crassopalpus (Hoff) , male. 61. Dorsal view of palp. 62. Lateral view of chela. Figs. 63-65. Mirochernes dentatus (Banks). 64, 65. Female. chela. 63. Male. 63. Lateral view of 64. Lateral view of chela. Dorsal view of palp. 65. 156 63 65 64 157 Figs. 66-68. Dinocheirus horricus, new species, male. 66. Dorsal view of palp. Lateral view of chela. 67. 68. Cheliceral galea. Figs. 69-70. Dinocheirus pallidus (Banks), male. 69. Lateral view of chela. view of palp. 70. Dorsal 158 68 69 70 159 Pigs. 71-74. Illinichernes distinctus Hoff, male. 71. Lateral view of chela. view of palp. Figs. 75-76. 72. Dorsal 73, 74. Palpal setae. Hesperochernes tamiae Beier, female. 75. Dorsal view of palp. 76. Lateral view of chela. Figs. 77-78. Hesperochernes ewingi (Hoff), male. 77. Lateral view of chela. view of palp. 78. Dorsal 160 77 78 161 Figs. 79-80. Hesperochernes lymphatus (Hoff), female. 79. Lateral view of chela. 80. Dorsal view of palp. Figs. 81-82. Hesperochernes amoenus Hoff. 82. Female. 81. Male. 81. Dorsal view of palp. 82. Lateral view of chela. 80 163 Figs. 83-84. Dactylochelifer copiosus Hoff, female. 83. Dorsal view of palp. 84. Lateral view of chela. Figs. 85-88. Chelifer cancroides (Linnaeus), female. 85. Lateral view of chela. view of palp. 86. Dorsal 87. Tergal halves. 88. Tarsal claw. 164 165 Figs. 89-91. Parachelifer monroensis, new species, female. 69. Tergites 7-9. view of palp. chela. 90. Dorsal 91. Lateral view of 166 167 Figs. 92-96. Icliochelifer nigripalpus (Ewing), male. 92. Lateral view of chela. view of palp. 93. Dorsal 94. Fourth coxa with anterolateral spur. tarsus of fourth leg. 95. Tibia and 96. Tergal halves. Figs. 97-98. Paisochelifer callus (Hoff), female. 97. Dorsal view of palp. and tarsus of fourth leg. 98. Tibia 168 93 92 95 96 97 PART III POPULATION STRUCTURE OF MICROBISIUM CONFUSUM HOFF IN A BEECH-MAPLE WOODLOT INTRODUCTION Few quantitative population studies of pseudoscorpions have been reported. Gabbutt (1967) examined three species of pseudoscorpions from beech litter in Oxon, England. Chthonius ischnocheles (Hermann) reached a peak of 619.7 individuals per square meter during August. Earlier pre­ liminary studies by Gabbutt and Vachon (1963) showed maximum densities of C. ischnocheles never exceeded 100 per square meter from oak litter in Devon, England. The maximum density for Roncus lubricus L. Koch and Neobisium muscorum Leach, occurring with C. ischnocheles from beech litter in Oxon, was nearly 300 and 85 individuals per square meter respectively. Maximum densities for all three species reached nearly 900 in August and were consistently around 500 per square meter. Gabbutt and Vachon (1965) found that N. muscorum, in sycamore-ash litter in Cheshire, England, barely exceeded 100 per square meter. Van der Drift (1951), on the other hand, reported densities of N. muscorum, from beech litter in Holland, to average only eight per square meter. The intent of this study is to quantitatively deter­ mine the population structure of MicrobiBium confusum 169 170 Hoff. * This species is widely distributed, occurring in « the northeastern and northcentral portions of the United States as far west as Colorado. This species is the most common pseudoscorpion present in Michigan, and is found % in a wide variety of habitats, forest litter and soil being the most common. METHODS AND MATERIALS * \ Tourney Woodland, a beech-maple climax woodlot, was selected as the site to study the life—history of Microbisium confusum. The woodlot is irregular in shape with a maximum length times width of approximately 500 by 200 meters. The site is contiguous with the Michigan State University campus proper. Within the woodlot a study area of 40 x 60 meters was plotted at 10 meter intervals. The area selected was generally level in terrain and was covered by a dense overstory of beechmaple . Approximately twice monthly, for a twelve-month period, litter and soil were sampled randomly from ten different sample sites. of a square meter. Litter samples were one-ninth As an equal area of soil would be too large in volume to effectively handle, soil cores 5.7 centimenters in diameter were taken directly beneath the litter samples to a depth of seven centimeters. Litter and soil samples.were removed to the laboratory in large plastic bags where the contents were examined using Tullgren funnel techniques. The extracted pseudoscorpions were prepared using the method described by Hoff (1949). RESULTS AND DISCUSSION * t A total of 182 Individuals was collected during this study of which there were 72 protonymphs, 43 deutonymphs, and 67 adult females. The population structure of Microbisium confusum is shown in Table 7. During this study no tritonymphs, or males were found. M. confusum was described by Hoff (1946c) on the basis of 127 females. The first record of a male was reported by Lawson (1969). It is thought that females of this species reproduce parthenogenetically. These females, according to Weygoldt (1969), may represent neotenic tritonymphs as the number of trichobothria present in the adults represents the number normally present in tritonymphs of other species. The total population, prior to an examination of each life stage, showed a spring and fall pulse. How­ ever, an examination of the component parts showed the composition of each pulse to differ. are shown in Figures 99-101. The component parts Winter months, December through March, were deleted from the figure as numbers of individuals collected during this period were not indicative of the actual population structure. 172 Perhaps TABLE 7.— The life stages and number per square meter of Microbisium confusum in Tourney Woodland during the period 5 January 1?69 to _ 3 January 1970. Date 5 19 8 23 10 23 8 20 4 26 10 24 8 28 17 5 19 10 24 7 21 5 19 3 January January February February March March April April May May June June July July August September September October October November November December December January Protonymphs 0 0 0 0 0 0 7.9 16.8 2.2 3.6 17.7 4.5 0 0.9 36.3 7.2 152.2 19.2 66.0 27.3 26.4 13.2 0 13.2 Deutonymphs 0 0 0 0 0 0 17.7 20.4 28.1 3.6 0 0.9 0 13.2 4.5 1.8 0.9 0 14.1 41.4 40.6 0 0.9 0 Adult Females 0 7.9 15.9 0 0 0 0.9 74.1 46.3 16.8 31.8 20.4 27.3 13.2 3.6 0.9 1.8 14.7 15.0 27.3 26.4 13.2 27.3 0 Total 0 7.9 15.9 0 0 0 26.5 111.3 76.6 24.0 49.5 25.8 27.3 27.3 44.4 9.9 154.9 23.9 95.1 96.0 •93.4 26.4 28.2 13.2 174 Figs. 99-101. Microbisium confusum Hoff. Protonymph density. density. 99. 100. Deutonymph 101. Adult female density. 175 99 130 70 — 50- 30- 10 — 100 7 0NO , / M. 9 0- 30- 10 - 101 7 0- 3O- 3 0- 10 - AUG. SEPT. OCT. NOV. APR MAY JUNE JULY 176 .-the collection made on 8 April also falls into the above category. Soil temperature on this date was 40°F. Rela­ tively high densities of all stages were present in November and April. During the winter months the den­ sities decreased and became erratic. No pseudoscorpions were collected during this period from frozen, soil or litter, or unfrozen litter above frozen soil. all life stages overwintered. However, Protonymphs were collected in unfrozen litter or soil in January, deutonymphs in December, and adult females during December through February. Gabbutt (1970) reported over-wintering mor­ tality to be negligible, and attributed the decrease in observed densities to migration into the soil and/or hibernation. He suggested that individuals encased in silken chambers are not extracted. During the period April through June the protonymph density was relatively low. No protonymphs were col­ lected in early July and only 0.9 per square meter were collected in late July. The protonymph density began to increase in August and by late September rapidly reached a peak of 152.2 per square meter. This sudden increase was followed by a sharp drop prior to another marked increase in late October. In November the proto­ nymph density remained relatively constant at about 27 per square meter. 177 Deutonymphs, on the other hand, reached a peak of 41.4 per square meter during early November. The deuto- nymph density remained at least 17.7 per square meter, exclusive of the winter months, through early May. The peak density for adult females was reached in late April and decreased to zero in September. The females reached a density of at least 14.7 per square meter during October and November. During the non-winter period protonymphs averaged 25.9, deutonymphs 12.5, and adult females 21.2 per square meter. The deutonymphs represented about one-third of the total nymphal population, while adult females repre­ sented a 1.7 increase over deutonymphs. This discrepancy in adults might be attributed to an extraction differ­ ential of different life stages or the occurrence of more than one generation of adults. With regard to the former, Gabbutt (1970) reported the efficiency of pseu­ doscorpion extraction not to exceed 80 per cent with protonymph and deutonymph numbers obtained without prejudice to tritonymphs and adults. If the latter were true, then the absence of adults in early September would require an explanation. Gabbutt (1970) explained the absence of females during certain periods of the year as being due to their construction of silken chambers for brood purposes. The absence of females during early September suggested females were in unextractable brood 178 •chambers. No females with eggs or embryonic stages attached were collected during this study. If more than one generation were present, then an increase of females would be expected to parallel the abrupt increase in protonymphs in late September. This increase in females did not occur until October. These data do not indicate that more than one gener­ ation is produced during a single year. Of six species examined by Gabbutt (1969) only one species, Neobisium muscorum, produced more than one generation per year, and this did not hold for all populations of this species. SUMMARY Twenty-nine species of pseudoscorpions axe reported from Michigan including two new species, Dinocheirus horricus and Parachelifer monroensis, and an undeter­ mined species of Pseudogarypus. In general, species tend to exhibit clear-cut dis­ tributional patterns. Still other species show disjunct patterns of distribution which could be the result of relict populations, phoresy, inadequate records, or misidentification of species. Eight species occur in both the Upper and Lower Peninsula, while only two species occur exclusively in the Upper Peninsula. Three species occur only from those counties adjacent to Indiana and Ohio. Nine species were taken from litter and soil. Thir­ teen species were collected from under bark of dead trees. Eleven species were collected within hollows of trees in association with rotten wood and debris. Often these trees contained remains of mammal, bird, and insect nests, or less frequently the active nests of a small mammal or bumble bees. Sixteen species were collected 180 during winter months, November through March. Sixteen samples yielded more than one species. Microbisium confusum is the most common pseu­ doscorpion in Michigan, and occurs in a wide variety of habitats, forest litter and soil being the most com­ mon. The abundance of this species in forest.litter and soil led to a population study in a beech-maple woodlot. Microbisium confusum reached a maximum density of 154.9 per square meter and dropped below 20, except for winter months, on a single occasion. The period of December through March was interpreted as a "suspended" period with an absence of marked growth and/or mortality. Protonymphs reached a peak density in Septem­ ber, deutonymphs in November, and adult females in late April. No males of Microbisium confusum were collected during this study, nor was this species collected in brood chambers or hibernacula. There was no evidence that more than one generation of M. confusum was pro­ duced per year, however, females present in the fall may represent more than one generation. APPENDIX 181 APPENDIX L” Map 30. Michigan map with county names LITERATURE CITED LITERATURE CITED Aristotle De Animalibus Historiae, 4:Cap. 7, Cap. 26 Banks, N . 1890. A new pseudoscorpion. Can. Ent. 22: 152. 1891. Notes on North American Chemetidae. Ent. 23: 161—66. Can. 1893. New Chernetidae from the United States. Can. Ent. 25: 64-67. 1895. Notes on the Pseudoscorpionida. Ent. Soc. 3: 1-13. Jour. N. Y, Barr, T. C. , Jr. 1967. Ecological studies in the Mammoth Cave Sys­ tem of Kentucky. I: The Biota. Int. Jour. Speleology 3: 147-204. Beier, M. 1930a. Die Pseudoskorpiones des Wiener Naturhistorischen Museum. Wiener Naturhistorisches Mus. Ann. 44: 199-222. 1930b. Neue Hohlen Pseudoscorpione der Gattung Chthonius. Eos 6: 232-7. 1932a. Pseudoscorpionidea. I. Subord. Chthoniinea et Neobisiinea. Das Tierreich 57: 1-258. 1932b. Pseudoscorpionidea. II. Subord. Cheliferinea. Das Tierreich 58: 1-294. 1932c. Revision der Chernetidae (Pgeudoscorp.) Zool. Jahrbucher, Abt. fur Syst. Okol. Geog. Tiere 64: 509-48. 1963. Ordnung Pseudoscorpionidea. Berlin. vi+313 pp. 182 Academie-Verlag, 183 Berger, E. W. 1905. Habits and distribution of Pseudoscorpionidae, principally Chelanops oblongus, Say. Ohio Nat. 6: 407-151 Brimley, C . S . 1938. The insects of North Carolina and their close relatives. N. Carolina Dept. Agri., Div. Ent. Raleigh, 560 pp. Chamberlin, J. C. 1929a. 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