SEASGNAL DISTRIBUTEON. OF HUMAN. FEEDWG MOSQUETC‘ES IN A SEWAGE SWAY ERRIGATION COMPLEX 'E‘hesis for the Degree of M. S. MECHKEAN ST 's’E UiélVERSETY WOMAS iOHh’. ZORKA 1 9 7 5 LIBRAR Z5 121%:st Q\ ' ABSTRACT SEASONAL DISTRIBUTION OF HUMAN FEEDING MOSQUITOES IN A SEWAGE SPRAY IRRIGATION COMPLEX By Thomas John Zorka A baseline study was conducted during the spring and summer months of 1973 and 1974 at the Michigan State University water quality management project spray irrigation complex. The purpose of this study was to gather information concerning the human biting insects indigenous to the project complex and their seasonal distribution. Methods of collection were landing counts using human bait during the day and CO2 baited miniature light traps at night. Aedes stimulans (walker), Aedes vexans (Meigen), and Aedes triseriatus (Say) were the three species of biting insects found to be indigenous to the spray irrigation complex area. SEASONAL DISTRIBUTION OF HUMAN FEEDING MOSQUITOES IN A SEWAGE SPRAY IRRIGATION COMPLEX By Thomas John Zorka A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Entomology I975 TABLE OF CONTENTS Investigation of l973 ................... Investigation of l974 . . . ................ SUMMARY AND CONCLUSION ...................... APPENDIX A. DAILY TEMPERATURES--l973 ................ B. DAILY PRECIPITATION--l973 ............... C. DAILY TEMPERATURES-~l974 ................ D. DAILY PRECIPITATION--l974 ............... LITERATURE CITED ......................... ii 28 3O 31 33 34 Table LIST OF TABLES Landing counts of female Aedes stimulans (Walker) in 1973 ........................... Landing counts of female Aedes vexans (Meigen) in l973 ................... A ........ Landing counts of female Aedes triseriatus (Say) in l973 ......................... Light trap catches (C02 baited) l973 ........... Landing counts of female Aedes stimulans (Walker) in 1974 ........................... Landing counts of female Aedes vexans (Meigen) in 1974 . . Landing counts of female Aedes triseriatus (Say) in 1974 ........................... Light trap catches (CO2 baited) l974 ........... Page 15 18 20 21 22 INTRODUCTION Mosquito species known to breed in Michigan sewage water impoundments and irrigation sites are not only pests in nearby communities but are capable of transmitting diseases such as dog heartworm and several types of viral encephalitis (Newson, 1974). Studies done at Belding, Michigan, sewage disposal project showed that initiation of spraying schedules enabled species not indigenous to the project site to establish themselves successfully in the project (Newson, 1974). The Michigan State University Water Quality Project is similar to the sewage disposal project at Belding, Michigan. This study was conducted during the spring and summer months of l973 and l974 at the Michigan State University water quality man- agement project. Its purpose was to accumulate baseline information concerning the species of man-biting mosquitoes indigeneous to the project area and their seasonal distribution prior to the initiation of water disposal operation. These data will be used in evaluating later observations after the onset of spray irrigation. This study was conducted in conjunction with another concerned with California encephalitis virus and its probable mammalian reservoir hosts. LITERATURE REVIEW There are many examples of major mosquito pest or disease problems associated with spray irrigation and waste disposal lagoons that were created because of the lack of planning. Typical examples of this are the large numbers of pest mosquitoes produced in the rice growing areas of Arkansas and the severe pest and mosquito—borne dis- ease problems present in parts of California where agricultural irri- gation currently is used extensively in what once was a semi-desert. The water management practices in these agricultural areas produced ideal habitats for certain mosquito species that formerly were rare or absent in these localities and have now become major problems, both as pest and vectors of human and animal pathogens (Smith and Enns, 1969). In Louisiana, waste lagoons used in connection with various livestock operations have been the major breeding sites for Culex pipiens guinquefasciatus (Say), an important vector of St. Louis encephalitis. As many as 1500 larvae per one pint dip were collected in these locations (Steelman, 1967). Smith and Enns (1969) reported that the most abundant and annoying mosquito species in Missouri oxidation lagoons were the Culex pipiens complex, Anopheles punctjpennis (Say), Culex erraticus (Dyar and Knab), and Aedes trivittatus (Coquil- lett), Aedes canadensis (Theobald), Aedes vexans (Meigen) and Aedes triseriatus (Say) were present less frequently, while Anopheles quadrimaculatus (Say) and Psorophora ferox (Humboldt) were taken occasionally. In Belding, Michigan, a spray irrigation program was started in the spring of 1973 to dispose of sewage water. Prior to the operation of the spray program the mosquito species breeding in the sewage ponds consisted primarily of Culex pipiens Linnaeus. With the beginning of spray operations in 1973, new mosquito breeding habitats were formed in the spray area and rapidly were occupied by nine additional mosquito species that either had not been present in the area or had existed there in small numbers. Eight of these species utilized only the irrigation plots. In 1974 all except one of the species breeding in the irrigation plots began to utilize the sewage lagoons as breeding sites (Newson, 1974). METHODS AND MATERIALS Immature stages of mosquitoes were collected with a one-pint enamel dipper with a three-foot, three-quarter-inch wooden dowel attached to the handle. Ten adult landing count stations were established within the wooded area located in the projected spray area (Figure l). Landing count collections were made for a period of ten minutes twice a week between 8 and 10 a.m., 2 and 4 p.m., and 7 and 9 p.m., every Tuesday and Thursday. Adult females were allowed to land on my exposed arms and face. After beginning to probe they were collected in an aspirator and then transferred into a killing tube. The females were then put into marked seamless cans for later identification and counting. Light trap collections were made with CDC (U.S. Public Health Service Center for Disease Control) miniature light traps. These compact traps were powered by six volt motorcycle batteries. Three light trap stations were Operated once each week on Wednesday at distances of 50, 100, and 200 yards from the edge of the wooded study area to determine how far mosquitoes would migrate at night from their daytime resting places (Figure 1). These traps were modified to kill the specimens collected. The lid ring of a one-pint preserving jar was fastened to the bottom of the trap by masking tape. A piece of Shell "No Pest Strip" was placed in the jar. The jar could easily be removed so that specimens could be collected. .mcowpmpm pczoo mcwvcmA use much pgmv4 .F mczmwu .um coop o b Ll. cowpapm gage p;m_4 - o cowympm pczou mcwc=M4 - x umom Ppwgucmm Hagadorn Road College Road xmpasou cowpmmegH macaw :mz \\\\\xx\\\\N\\\\\VNNNNNNNN\\\\\N\\\\\\N~\\\NN\NNNN\NN\NNN-~\\NN\V\\\\NN\N\N\\\N\\\N\\\\\N __ .3 RESULTS Investigation of 1973 In Tables l-3, the diurnal biting activity and seasonal distribution of the mosquito fauna indigenous to the spray irrigation complex in 1973 are shown, including the approximate dates for the initial appearance in the spray area of the species collected during that year. Only three species were collected in any appreciable numbers: Aedes stimulans (Walker), Aedes vexans (Meigen) and Aedes triseriatus (Say). Female Anopheles pynctipennis (Say) were collected twice in August in landing counts and larvae were collected once in August from a rain—filled tire rut. Since these were the only Anopheles punctipennis (Say) collected no seasonal distribution was established. Aedes stimulans (Walker) was the first species of mosquito to appear within the study during 1973. Its emergence from breeding sites within the wooded area first occurred late in the fourth week of May (Table 1). On May 29 adult mosquitoes were observed in the wooded area but they did not attempt to bite and no landing counts were taken. Emergence of Aedes stimulans (Walker) usually occurs between April and June, depending upon the geographic locale. Obrecht (1949) reported emergence of Aedes stimulans (Walker) in Michigan occurs during May. Warm temperatures of between 59 and 75°F prior Table 1. Landing counts of female Aedes stimulans (Walker) in 1973 ’Time Period Date 8:00-10:00 a.m. 2:00-4:00 p.m. 7:00-9:00 p.m. May 29 O O O 31 180 187 188 June 5 154 153 156 7 147 153 152 12 142 145 151 14 139 146 152 19 137 138 140 21 126 131 144 26 124 138 140 28 92 128 139 July 3 115 137 141 5 122 127 133 10 143 143 146 12 127 131 129 17 135 136 159 19 128 134 138 24 108 124 139 26 114 110 127 31 87 71 62 August 2 73 68 69 7 12 14 14 9 11 13 15 14 6 7 8 16 6 4 6 21 3 4 2 23 2 3 4 28 0 O O 30 0 0 0 Table 2. Landing counts of female Aedes vexans (Meigen) in 1973 Time Period Date 8:00-10:00 a.m. 2:00-4200 p.m. 7:00-9:00 p.m. June 5 129 130 134 7 118 124 126 12 53 50 56 14 47 49 48 19 25 26 27 21 23 26 28 26 14 16 17 28 10 12 14 July 3 11 13 10 5 8 6 8 10 7 7 8 12 3 4 4 17 2 4 5 19 61 69 73 24 48 50 53 26 39 43 44 31 37 31 35 August 2 23 29 31 7 11 9 9 9 8 ll 13 14 3 6 . 4 16 4 6 6 21 2 3 3 23 2 5 2 28 3 5 6 3O 41 43 52 Table 3. Landing counts of female Aedes triseriatus (Say) in l973 Time Period Date 8:00-10:00 a.m. 2:00-4:00 p.m. 7:00-9:OO p.m. June 7 43 47 48 12 20 21 22 14 18 16 20 19 21 22 25 21 20 19 22 26 19 21 23 28 18 17 21 July 3 17 18 24 5 16 14 19 10 14 14 15 12 13 15 12 17 13 11 14 19 18 23 26 24 19' 17 14 26 15 12 11 31 9 11 12 August 2 11 11 12 7 4 4 3 9 4 4 5 14 1 2 4 16 2 0 l 21 l 2 4 23 1 0 l 28 0 O 0 3O 0 0 O 10 to its emergence were important in triggering its emergence (Appendix A). The abundance of female adult Aedes stimulans (Walker) made it impossible to stay in the wooded area for any length of time. Five- hundred fifty-five females were taken in 30 ten-minute landing counts on May 31 (Table l). Aedes vexans (Meigen) was the next species to appear in the spray irrigation area. This species was first taken in landing counts during the collections made in the first week in June. The emergence of this species was not quite as spectacular as that of Aedes stimulans (Walker) but its presence was noticed by its very painful bite. Three- hundred and ninety-three females were collected on June 5 (Table 2). No consistent specific emergence dates can be established for Aggg§_ ygxap§_(Meigen) because it is a floodwater mosquito with more than one generation per year and egg hatch is dependent upon the periodic flood- ing of oviposition sites. In Hancock County, Mississippi, Aedes vexans (Meigen) was reported to have occurred in all stages each month of the year (Harden and Poolson, 1969)._ The first adults usually appear from early April to June in more northern climes. Aedes triseriatus (Say) was first collected in landing counts on June 7 (Table 3). It was considerably less numerous than Aggg§_ ygxap§_(Meigen) with only 145 females taken in landing counts. However, it is more significant from a medical standpoint because it has been incriminated as a vector of California encephalitis (Thompson et al., 1972). 11 Diurnal landing count collections from June through August showed Aedes stimulans (Walker) to be the most numerous species in the wooded area with Aedes vexans (Meigen) and Aedes triseriatus (Say) being the next and least populous, respectively. During June and July the large numbers of Aedes stimulans (Walker) taken in landing counts indicated that it was a very long lived species and also a very persistent biter. It is one of the most abundant and annoying woodland species of the northeastern United States and eastern Canada. The high biting activity can be seen in the large totals taken in landing counts for each of these months (Table l). A§g§§_ stimulans (Walker) was observed to be very active during any time of the day but the peak of biting frequency appeared to be in the evening hours towards dusk. The females very seldom left their wooded habitat during the day to seek a blood meal, although on occasion in the early morning hours, females were observed seeking blood meals. Aedes vexans (Meigen) collectibns during this same two-month period appeared to indicate the presence of two generations. In June, 1,302 female Aedes vexans (Meigen) were taken in landing counts. The population, as indicated by the biting collections, began to drop off during the last weeks of June and the early weeks of July (Table 2). On July 19, 203 females were collected in landing counts, indicating that a summer generation had emerged and moved into the study area. This emergence was probably a result of a heavily localized rainstorm that occurred nine days prior to this emergence (Appendix B). It was assumed that Aedes vexans (Meigen) migrated into the study area because 12 no breeding sites were found and this species can migrate long distances to seek blood meals and resting habitats. Aedes vexans (Meigen) is considered to be a floodwater mosquito. Immature stages may be found in many situations such as roadside puddles, vehicle ruts, woodland pools, borrow pits, and sewage lagoons. Breeland et a1. (1961) reported having found larvae in grassy rain pools, roadside ditches, and flooded river bottoms. The peak diurnal biting period for Aegg§_ ygxap§_(Meigen) was observed to be during evening hours although this species is a persistent biter any time of the day (Table 2). Aedes triseriatus (Say) was collected during June and July in fairly consistent numbers. In June and July, 503 and 384 females were collected, respectively, making it the least abundant species of the three collected (Table 3). This species is multivoltine. Larval samplings during the second week in July from holes in trees in wooded area indicated the presence of small populations of Aedes triseriatus (Say) larvae that could serve to maintain the adult population. It is one of the most widely distributed treehole-breeding mosquitoes in North America. This species breeds in still water rich in organic matter with favored breeding sites being stumps and tree-holes. Larvae have been found in treeholes of gums, yellow popular, hackberry, pecans, black willow, red maple, ironwood, hop hornbeam, ash, oaks, and elms. They are frequently found in or near wooded areas in artificial containers such as tin cans, glass jars, automobile tires, hollow fence posts, and_debris choked gutters (Breeland et al., 1961). Larvae also have been found in pitcher plants in Ontario (Stewart and McWade, 1961). 13 Snow (1949) reported that larval development under field conditions requires three to nine weeks. The duration of the developmental period is mainly a function of water temperatures. Under laboratory conditions with water temperatures at 80°F larval development and pupation occurred in ten days. Larvae have been found associated with those of Anopheles barberi Coquillett, Culex restuans Theobald, Orthopodomyia alba Baker, 9, signifera (Coquillett) and Toxorhynchites septentrionalis (Dyar and Knab) in collections taken in the Tennessee Valley (Breeland et al., 1961). Landing counts in August showed the population of Aedes. stimulans (Walker) to be still active but declining in numbers. August 23 was the last time that any females of this species were collected in the study area in 1973 (Table l). Obrecht (1949) reported that females may persist in Michigan in large numbers as late as August. Carpenter and LaCasse (1955) reported that this species has been encountered as late as September. Aedes vexans (Meigen) began to decline in numbers during August until the fourth week when a new generation emerged and was assumed to have migrated into the study area (Table 2). The second generation emerged eight days after a .78 inch rainfall had fallen on August 21 (Appendix B). The daily maximum temperatures during this eight-day period ranged from 72 to 95°F (Appendix A). Gjullin (1950) reported that when water tempera- tures approximate 80°F, larval stages may be completed within five days with adults emerging on the seventh day after a two-day pupal period. No land-counts were taken in this area after the fourth week 14 of August but small numbers of Aedes vexans (Meigen) females were observed seeking blood meals in late September. The population of Aedes triseriatus (Say) had completely disappeared by the third week in August with only small numbers being collected at this time (Table 3). During August, five Anppheles punctipennis adults were collected in landing counts and fifteen larvae were collected in a rain-filled tire track in the wooded area. Light trap collections (Table 4) were used to determine the night activity and flight range of the species present in the wooded area. Aedes stimulans (Walker) and Aedes vexans (Meigen) were taken in C02 baited light traps during most of the summer. In trap no. 3 (Figure l), which was located one-eighth of a mile (220 yards) from the edge of the wooded area, 118 female Aedes stimulans (Walker) were collected during June and July but none were collected in August (Table 4). This species may migrate long distances in search of blood meal. Matheson (1944) reported taking marked adults at least two miles from any known breeding site. Aedes stimulans was attracted to the traps at 50 and 100 yards. One-hundred forty-seven and one- hundred thirty-five female Aedes stimulans (Walker) were collected from traps no. 1 and 2, respectively, from the second week in June to the first week in August (Table 4). Light traps were the primary source for detecting second generations of Aedes vexans (Meigen) that were assumed to have migrated into the spray irrigation complex. Adult females are known to migrate long distances from their breeding sites to seek a blood meal. 15 .qucmz ONNV m .02 amcF new ”qucmx oon N .02 amLF ”chcmx omv F .02 qmch o o 0 NF qF oF o o o mN o o o o o o o o o NN o o o o N N o oo o mF o o o m a m o o o w o o o m m m o m F F Fmsms< o o 0 NF mF oF o FF a mN o o N mm Fm me FF NF NF NF F m w o o 0 NF mF ON FF 0 N m o m N FN FN NN v Fqu o o v N m a Fm mN Fm FN N N m w o m Fm mm Fe ON mean m .02 N .02 F .02 m .02 N .02 F .02 m .02 N .oz F .oz open ach amLF mqmcF Fxmmv mzmecmchu mmvm< Acmmszv mcmxm> mmum< Fememzv mcszerm mmvm< mumF Fummea Noov Managua away “SUFS .3 anmF 16 Stage et a1. (1938) recovered marked Aedes vexans (Meigen) females three miles from the release point. The first summer generation in the study area was observed in collections made during the third week in July 1973 when 119 females were collected in all three traps (Table 4). The second summer generation appeared on August 29 when 41 females were collected in the three traps. This generation was assumed to appear with marked, abrupt increases in light trap col- lections and landing counts as compared with the previous collecting period. Aedes triseriatus (Say) was only slightly active at night during the 1973 summer season. A total of 26 females were collected during this time. Only three were collected from the trap set at one- eighth of a mile from the edge of the wooded area while most of the females were collected in the trap set at fifty yards from the edge of the wooded area (Table 4). Investigation of 1974 In 1974, the study was begun in early April. During this period there were large vernal ponds formed in depressions by melted snow and early season rains. These contained large numbers of first and second instar larvae of Aedes stimulans (Walker). In the northern two-thirds of Indiana, Aedes stimulans (Walker) occurs in beech-maple forests developing in depressions which receive partial shade and are lined with leaves (Siverly, 1972). Often drainage and roadside ditches are utilized as breeding sites. Larvae of this species have been found 17 in woodland pools with Aedes fitchii (Felt and Young) and Aedes excrucians (Walker). In Delaware county, Indiana, Siverly (1972) reported that these three species occur in an approximate 80:15:5 ratio, respectively. Larval development for this species was very slow, mainly because of cold temperatures. By the fourth week in April most of the larvae had developed to the fourth instar and pupation occurred during the first and second weeks in May. This was the first species in the complex and was first taken in landing counts on May 30. Five-hundred sixty-three adult females were taken in landing counts during this period (Table 5). The emergence dates of this species in 1973 and 1974 were approximately the same. Aedes vexans (Meigen) and Aedes triseriatus (Say) were both observed in the complex area in the first part of the first week in June of 1974, which is very similar to that observed in 1973. The 553 Aedes vexans (Meigen) females taken in landing counts on June 4 of 1974 was higher than the 393 adult females collected during the same period in l973. Aedes triseriatus (Say) emerged a little earlier in 1974 than in the previous year but the population was initially not as abundant as in 1973 with only 143 biting adult females being collected as compared to 203 in 1973 (Table 7). In the first week of June the numbers of Aedes stimulans (Walker) taken in landing counts dropped off sharply from the week before (Table 5). The decline continued until the third week in June when it stabilized for the next three weeks before again dropping (Table 5). Aedes stimulans (Walker) was still collected in landing 18 Table 5. Landing counts of female Aedes stimulans (Walker) in 1974 Time Period Date 8:00-10:00 a.m. 2:00-4:00 p.m. 7:00-9:OO p.m. May 30 182 184 197 June 4 84 87 91 6 76 74 75 11 60 58 62 13 54 57 59 18 47 45 47 20 41 44 49 25 40 42 43 27 42 43 46 July 2 43 41 46 4 42 41 48 9 38 33 39 ll 34 36 36 16 41 40 39 18 38 39 39 23 26 21 27 25 20 23 24 30 14 12 15 August 1 ll 7 10 6 4 5 4 8 3 3 4 13 3 2 3 15 2 5 5 20 2 3 3 22 l 3 3 27 O O 0 29 0 0 O 19 counts in the latter part of the third week of August. The very hot and dry summer with a two-week rainless period during July may indicate that this mosquito is able to survive well in adverse circumstances. Aedes vexans (Meigen) females were present this year for only six weeks. Initially there was a very large population but it decreased sharply in the second week in June and_the decline continued until the second week in July, after which no adult females were collected in landing counts. This species did not reappear during the rest of the summer (Table 6). The probable reason that the resident population of this species died off at such an early period was the lack of rain during the summer of 1974 (Appendix D). Aedes triseriatus (Say) was collected in landing counts in the wooded area until the second week of July (Table 7). Again, the lack of rainfall probably was responsible for keeping the population much smaller than in 1973. Only 465 adult females were collected during the whole summer while 504 were collected in the June 1973 period. Anopheles punctipennis (Say). Aedes canadensis (Theobald), Coquillettidia perturbans (Walker) and Psorophora ferox (Humboldt) were collected in landing counts during August but the numbers collected were not large enough to indicate any seasonal distribution. Light trap collections showed that night biting activity of all species was limited to the month of June in 1974 with only two Aedes stimulans (Walker) females collected during the first week in July (Table 8). Seventy-eight Aedes stimulans (Walker) and 20 Table 6. Landing counts of female Aedes vexans (Meigen) in l974 Time Period Date 8:00—10:00 a.m. 2:00-4:00 p.m. 7:00-9:OO p.m. June 4 180 180 190 6 174 164 163 ll 83 85 89 13 76 77 79 18 43 45 46 20 42 39 44 25 34 35 32 27 33 31 30 July 2 14 16 11 4 10 10 12 9 9 6 7 11 4 5 8 16 0 0 0 l8 0 O 0 23 O O 0 25 0 0 O 30 O O 0 August 1 0 0 0 6 O O 0 8 0 O 0 l3 0 0 O 15 O O O 20 0 0 0 22 0 O O 27 O O 0 29 O 0 0 21 Table 7. Landing counts of female Aedes triseriatus (Say) in l974 'Time Period Date 8:00-10:00 a.m. 2:00-4:OO p.m. 7:00-9:00 p.m. June 4 23 26 28 6 21 23 22 11 21 19 20 13 20 18 23 l8 14 12 15 20 13 ll 16 25 12 10 12 27 9 ll 10 July 2 5 6 8 4 4 5 7 9 3 4 7 ll 2 2 3 l6 0 O 0 18 O O 0 23 0 0 O 25 0 O O 30 O O 0 August 1 O 0 0 6 0 0 0 8 O O O 13 O O 0 15 O O 0 20 0 0 0 22 O 0 0 27 0 O 0 29 O O O 22 o o o o o o mN o o o o o o FN o o o o o o «F o o o o o o N pmzmz< o o o o o o Fm o o o o o o «N o o o o o 0 FF 0 o o o o 0 0F c o o o o N N Fsz o o N o m N 0N a m o v w o mF VF NF 0N m NF FF NF me we mm «N mN mN m mczq F.mux ONNV F.mu» oon F.mus omv F.mu» ommv F.mu» oon F.mu» omv mung m .oz amcF N .oz amLF F .oz amLF m .oz QmLF N .oz mock F .oz amLF chmszv mcmxm> mmum< Acmemzv mcmFaeFum mwum< N eNmF vamen ouv magupmo away pngs .m aanF 23 one-hundred and forty Aedes vexans (Meigen) were collected at this time. After the first week in June the numbers of these two species began to drop sharply (Table 8). No Aedes triseriatus (Say) were collected in light traps during the 1974 summer. SUMMARY AND CONCLUSION In May through August of 1973 and 1974 an investiation was conducted at the Michigan State University water quality management project spray irrigation complex to determine the species of man- biting mosquitoes indigenous to the complex and their seasonal distribution. Data obtained in these two years indicate that Agg§§_ stimulans (Walker), Aedes vexans (Meigen), and Aedes triseriatus (Say) were the three major species of mosquitoes found in the wooded area of the spray irrigation complex. Seasonal distribution studies showed Aedes stimulans (Walker) to be univoltine and the dominant species in the wooded area, as determined by the number of adults collected in landing counts for both years. This species appeared to have a long life span that lasted from the fourth week in May to the third week in August of both years. It was a very painful biter during any part of the day to anyone present in the wooded area. CO2 baited light trap collections showed that Aedes stimulans (Walker) may migrate at least an eighth of a mile at night from its usual diurnal resting sites. Aedes vexans (Meigen) was the second most abundant species in the wooded area of the spray complex. Adults appeared in the first week of June of both years. During July and August of 1973 24 25 summer generations were produced which were very important in maintaining the population in the wooded area. This species was a very painful biter during any part of the day. Light trap col- lections showed that it may migrate at least an eighth of a mile at night. In 1974 no summer generations were produced, presumably due to the long dry spell in July and August. Adults of the least abundant species, Aedes triseriatus (Say), appeared in the first week in June of both years. This species was active during the day and evening hours and was most active at dusk. Very little night activity was observed in light trap collections. In 1974, Aedes triseriatus (Say) had a very short season of six weeks because of the long, dry and hot period in July and August. At present there appears to be no real potential health threat generated by the numbers of the mosquito species now indigenous to the project site, but with the initiation and main- tenance of a spray schedule in and around the wooded area, potential health factors could emerge. With the assumption of a routine spray irrigation operation new breeding habitats may appear. Spraying in the wooded area can be expected to maintain water in tree holes and containers through the summer, thereby increasing the breeding sites not utilized by Aedes triseriatus (Say). Spray water in this same area will also modify the water depth fluctuations in the vernal ponds in the wooded area, which may either enhance or reduce the egg laying sites of Aedes stimulans (Walker). There also is a possibility that flooding caused by spraying will form breeding 26 sites for Aedes vexans (Meigen) and may create ideal conditions for the establishment of species not indigenous to the spray irrigation complex. Coupled with the possibility of an increase in the numbers and species that may occur in the spray complex is the potential for increases in arthropod-borne viruses and parasitic life forms that are transmitted by mosquitoes. Serological surveys and clinical observations have indicated that California encephalitis and dog heartworm, Dirofilaria immitis, are present in East Lansing. Furthermore, the serological surveys from the project area indicate that an enzootic transmission cycle of California encephalitis virus is present in the project site (Wildie, 1975). Aedes triseriatus (Say) has been implicated as the major vector of the La Crosse subtype of California encephalitis (CE) in the upper midwestern United States. Epidemiological studies by Pantuwatama et a1. (1974) in Wisconsin have indicated that the La Crosse subtype is maintained in nature by an Aedes triseriatus--small mammal transmission cycle. Close association has been shown between Aedes triseriatus (Say) and chipmunks, Tamias striatus, and gray squirrels, Sciurus carolinensis. The medical importance of Aedes stimulans (Walker) has not been fully investigated and assessed. In California group virus studies conducted between 1943 and 1970, Jamestown Canyon and Snowshoe Hare subtype of California encephalitis were isolated from Aedes stimulans (Walker) females (Sudia and Newhouse, 1971). Sather (1968) also reported that California encephalitis virus had been isolated from this species. Sudia et a1. 27 (1971) reported that six subtypes of California encephalitis virus have been isolated from Aedes vexans (Meigen), including six isolations of La Crosse and thirteen Trivittatus subtypes of California encepha- litis. The initiation of spraying sewage water in the breeding places of Aedes stimulans (Walker) and Aedes triseriatus (Say)will enhance the breeding potentials of these two species and may create new breeding sites for Aedes vexans (Meigen). This will increase chances of human exposure to this virus. The incidence of dog heartworm has been continuously rising in Michigan in the recent years and, although no mosquito vector has yet been incriminated as the main vector of this nematode, the species breeding in the project must, at this time, be considered as potential vectors (Newson, 1974). It is premature to predict the future effects of sewage water spray irrigation in the spray irrigation complex in terms of health hazards, but, if spraying does produce an overabundance of mosquitoes that cause more discomfort to neighboring communities, there will likely be a need for mosquito control measures, and, perhaps, restricted use of the project site. APPENDICES APPENDIX A DAILY TEMPERATURES--1973 Date \OCDVOWU‘l-wa-J Maximum APPENDIX A DAILY TEMPERATURES--1973 Minimum Date 53° June 1 49 2 36 3 34 4 31 5 37 6 53 7 53 8 50 9 52 10 46 ll 42 12 39 13 34 14 35 15 35 16 32 17 28 18 47 19 4O 20 41 21 49 22 55 23 44 24 51 25 46 26 50 27 55 28 52 29 49 30 43 28 W Minimum 32 Daily Temperatures--Continued Date Maximum Minimum Date Maximum Minimum July 1 85 56 August 1 76 52 2 87 65 2 79 59 3 9O 73 3 78 64 4 91 67 4 77 52 5 74 53 5 76 56 6 81 56 6 82 55 7 88 56 7 81 52 8 92 65 8 81 62 9 92 68 9 8O 6O 10 81 69 10 81 58 ll 79 72 ll 82 67 12 82 47 12 83 6O 13 81 59 13 82 63 14 95 72 14 79 54 15 95 62 15 81 54 16 81 54 16 82 6O 17 83 56 17 76 61 18 87 70 18 81 53 19 87 66 19 85 57 20 87 52 20 89 62 21 80 45 21 88 63 22 80 58 22 86 62 23 71 58 23 86 65 24 81 56 24 80 57 25 81 60 25 8O 48 26 87 62 26 89 58 27 87 66 27 89 65 28 89 53 28 71 51 29 89 59 29 75 51 30 78 56 30 78 57 31 78 54 31 79 60 APPENDIX D DAILY PRECIPITATION--1974 D N—a-a—ad .J—i—l—lu—l _a GI 0&0me 01Ade 0100on macaw—u NNNNN U'IDWN-d APPENDIX B DAILY PRECIPITATION--l973 my. .63 Trace Trace .03 Trace .50 .10 .06 Ioé .02 June :55 :09 .09 Trace .98 30 July Trace .45 :5; 265 :66 :65 .04 .02 .14 Trace niéée .23 August Trace Trace :56 Iéi .78 Trace :53 _. E? OOWNO’S macaw—I ._I_I.—I._a #WNH 15 APPENDIX D DAILY PRECIPITATION--1974 Dex .05 :0} .17 2&5 .05 .44 .19 Trace Trace .37 1.35 .46 Trace :07 .70 June Iéé 33 July Ibé Iéé 255 Trace :05 .01 :05 August 256 Trace .04 Iié .O7 .05 .06 .O4 203 1:25 Trace LITERATURE CITED LITERATURE CITED Breeland, S.G., W.E. Snow, and Eugene Pickard. 1961. Mosquitoes of the Tennessee Valley. J. Tenn. Acad. Sci. 36: 249-319. Carpenter, S.J., and W.J. LaCasse. 1955. Mosquitoes of North America (North of Mexico). Univ. Of Calif. Press, vi + 360 pp., illus. Gjullin, C.M., W.W. Yates and H. H. Stage. 1950. Studies of Aedes vexans (Meigen) and Aedes sticticus (Meigen) floodwater mosquitoes in the Lower Columbia River Valley. Ann. Ent. Soc. Amer. 43: 262-275. NF“"""“1 Harden, F.W., and B.J. Poolson. 1969. Seasonal distribution of mosquitoes of Hancock County, Mississippi, 1964-1968. Mosquito News 29: 407-14. Newson, H.D. 1974. Species succession, biology and faunal relationships of mosquitoes associated with sewage spray irrigation operation. Unpublished Report to Environmental Protection Agency, 11 pp. Obrecht, C.B. 1949. Notes on the distribution of Michigan mosquitoes (Diptera: Nematocera). Amer. Mid. Nat. 41: 168-73. Pantuwatana, Somsak, W.W. Thompson, D.M. Watts, T.M. Yuill and R.P. Hanson. 1974. Isolation of Lacrosse virus from field Aedes triseriatus larvae. Amer. J. of Trop. Med. and Hyg. 23: 246-50. Sather, Gladys. 1968. Classification of the California Encephalitis virus group. Vector Control Briefs, Center for Disease Control, Atlanta, Georgia. Issue No. 21: 9-10. Siverly, R.E. 1972. Mosquitoes of Indiana. Indiana State Board of Health, 64-70. Smith, L.W., and W.R. Enns. 1967. Laboratory and field investigations of mosquito populations associated with oxidation lagoons in Missouri. Mosquito News 29: 462-66. Snow, W.E. 1949. Studies on portable resting stations for Anopheles uadrimaculatus in the Tennessee Valley. J. Nat. Mal. Soc. 8: 336-43. 34 35 Steelman, C.D., J.M. Gassie and B.R. Craven. 1967. Laboratory and field studies on mosquito control in waste control disposal lagoons in Louisiana. Mosquito News 27: 57-59. Steward, C.C., and J.W. McWade. 1960. The mosquitoes of Ontario (Diptera: Culicidae) with keys to the species and notes on distribution. Proc. Ent. Soc. Ont. 91: 121-88. Sudia, W.D., V.F. Newhouse, C.H. Calisher and R.W. Chamberlain. 1971. California group arboviruses: Isolations from mosquitoes in North America. Mosquito News 31: 576-97. L Thompson, W.H., R.O. Anslow, R.P. Hanson and B.R. Defoliart. 1972. LaCrosse virus isolations from mosquitoes in i Wisconsin, 1964-1968. Amer. J. of Trop. Med. and Hyg. I 21: 90-96. ' Wildie, J.A. 1975. "Vertebrate-mosquito relationship in a water quality management project." Unpublished master's thesis, Michigan State University. 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