Life History Characteristics of Wyeomyia Smithii from New Jersey
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Journal ofVector Ecology 24(1): 70-77 1 799H4 Life History Characteristics of Wyeomyia smithii from New Jersey Farida Mahmood and Wayne J. Crans Department of Entomology, Rutgers the State University 180 Jones Avenue, New Brunswick NJ 08901-8536 Received 29 July 1998; Accepted 72 October 1998 ABSTRACT: We colonized Wyeomyia smithii (Coquillett) from southern New Jersey and studied life history characteristics in the laboratory. Males and females showed no significant difference in time spent from first to third instar, but female larvae remained in fourth instar 2.1 days longer than males. At 22+/-2C females emerged 22.6+/-3 days after egg hatch; males emerged approximately two days earlier. Male emergence peaked five hours after dawn; females showed a trend to emerge late in the day. Rotation of male terminalia was completed 9 to 11 hours after emergence. Females were capable of mating immediately after emergence. Wyeomyia smithii females laid their first egg batch four to six days after emergence. Females were capable of laying up to seven batches ofeggs, however the mean number ofeggs per oviposition decreased significantly as the number of oviposition cycles increased. Keyword Index: Wyeomyia smithii, larval development, emergence rhythms, sexual maturation, fecundity. INTRODUCTION rates of females and males, diel emergence rhythms, sexual maturation of both sexes, ovarian development, Wyeomyia smithii (Coquillett) is distributed in and fecundity of females. eastern North America from the Gulf of Mexico to Labrador and northeastern Saskatchewan (Bradshaw MATERIALS AND METHODS and Holzapel 1996). The mosquito completes its immature development in aquatic habitat offered by the Colony Maintenance leaves of the purple pitcher plant, Sarracenia purpurea A colony of Wy. smithii was established from third- L. Dodge (1947) felt that Wy. smithii was limited to instar larvae that were collected from a stand of S. the northern subspecies of the plant, S. p. gibbosa purpurea growing in the New Jersey pine barrens in (Rafinesque) and that Wyeomyia haynei followed the Ocean County, NJ (latitude 39 50'; longitude 74 15'). range of the southern subspecies, S. p. venosa Larvae were collected from the leaf liquor of plants in (Rafinesque). The two species are now believed to late March 1997 and reared in enamel pans containing represent a single species, Wy. smithii, that displays a deionized water and fed a mixture of 20 parts ground north-south geographic dine of morphological and life hamster food, 12 parts liver powder, and part brewer's history characteristics (Bradshaw and Lounibos 1977, yeast. We kept the adults in a 0.3 m3 cage at a 16L:8D Bradshaw and Holzapfel 1983). photoperiod that included 1.5 hours of dusk and hour Northern populations of Wy. smithii overwinter as of dawn provided by a 15 watt incandescent bulb. larvae, frozen within the leaves of the host plant (Smith Adults were given constant access to 10% sucrose 1902), and are obligatorily autogenous throughout their solution on cotton wicks as a source of carbohydrate and life span (O'Meara and Lounibos 1981). Southern were never offered blood. populations are autogenous for their first egg batch but generally require blood for subsequent batches Larval Development. (Bradshaw 1980). To quantify immature life history characteristics, We colonized Wy. smithii from southern New Jersey we reared 96 individual larvae at 22+/-2C in separate and used the F^ generation to study various aspects of wells of 24 well (2.0 ml each) Falcon(R) culture plates. its biology, such as differences in larval developmental We placed a single first-instar larva in each well with 1.5 June, 1999 Journal 'ijll^&f-toK^ology 71 ml of deionized water and placed covers on each unit rotation. Terminalia rotation was checked until all throughout the rearing process. The food mixture used of the males in remaining cohorts had terminalia to rear the colony was mixed in slurry, and 100 ml was rotated to 180. We also examined similar groups of added to each well. The wells of the rearing plates were males to determine whether the terminalia rotated skimmed daily with a paper towel to remove scum clockwise or counter clockwise. Direction was formed by bacterial growth. Deionized water was determined visually by noting the position ofthe heavily added after the skimming process to replace water lost scaled light pleuron of segment 8 in relation to the black to evaporation. Food was added to individual wells tergum and white sternum of segment 7 (Fig 1). We every other day. We daily recorded the number of dead calculated the percentage of males in each class of larvae and kept a record of exuviae to determine day of terminalia rotation by dividing the number of males in molting. No food was added after pupation and adults a rotation class by total number of males checked for emerged directly in the wells of the covered culture that time interval. plates. The date and sex ofeach indi vidual was recorded at emergence, labeled by well number, and frozen in Sexual Maturation of Females individual Wasserman tubes. Wing length of both sexes We placed 22 female pupae in a 250 ml beaker and was measured with an ocular micrometer (Mahmood et allowed them to emerge in a 3.8 liter canon with 20, al. 1997) and compared with a two tailed t-test (P < five-day-old virgin males to determine if newly emerged 0.05). females mate with sexually mature males. Similarly, we We calculated the mean duration for each larval allowed 46 female and 39 male pupae to emerge together instarby sex and compared differences in instar duration to determine if newly emerged adults were able to mate. for each sex a using two way ANOVA and Tukey's Both groups were provided with 10% sucrose solution. HSD test. Survivorship to the adult stage was calculated After 30 hours, we dissected the spermathecae of each as total number of adults divided by the total number of female in saline (Hayes 1953) for the presence of sperm. first-instar larvae at the onset of the experiment. To determine the effect of age on female mating ability, we allowed groups of female and male pupae to emerge Diel Emergence Rhythms in a series of separate 3.8 liter paper cartons. Individual We allowed females to oviposit on the water surface groups of virgin females were isolated from males for 1, of 26.5 x 15.5 cm white enamel pans placed in the 3,4, and 5 days. Virgin males used formating experiments colony for 24 cage hours. Larvae that hatched from were four days of age. Four to six replicates of 10 these eggs a 24-hour during period were transferred to females in each of the above age classes were kept with 36.0 x 23.0 cm enamel and pans reared to pupation. A 10 virgin males for 24 hours. The following day, we total of 600 that pupae were collected on six different dissected the spermathecae of all females and recorded days and placed in 500 ml beakers containing deionized the number of inseminated females. The percentage of water and covered with nylon netting was observed for inseminated females (number inseminated in the sample/ adult Time of emergence. emergence was recorded at total number dissected) in different age classes were one-hour intervals for 24 hours for each group. Cohorts compared by one way ANOVA after arcsine of adults that emerged during each hourly interval were transformation and significant differences in means placed in separate 0.5 liter cartons and later recorded by were compared by Tukey's HSD test. numberand sex. Diel emergence rhythms were calculated as percent of total adults of each sex emerging during a Ovarian Development one-hour interval divided by the total number of adults We kept 100 newly emerged females and 100 of that sex that emerged over a 24-hour period. newly emerged males together in a 3.8 liter carton for 72 hours and provided 10% sucrose solution as a source of Sexual Maturation of Males energy. From this group we examined follicular Groups of 10 to 24 males were isolated within one development in the ovaries of five mated females at 24, hour of emergence in separate 0.5 liter paper cartons. 48, and 72 hours from the time of emergence. In All of the insects were anesthetized with chloroform in addition, we examined the ovaries offive newly emerged individual cartons at intervals from 0 to 12 hours after females that had not been exposed to males. We emergence to record progression in rotation of their recorded length and width of five indi vidual ovarioles in terminalia. We followed the classification system of each female and the length of the area occupied by yolk Khan and Reisen (1977) and recognized four stages of using the methods ofMahmood et. al. (1991). Significant rotation (Fig. I): 0 to <45 1) rotation, 2) 45 to 90 changes in ovarian development over time were rotation, 3) 90 to 135 rotation, and 4) 135 to 180 determined by comparing changes in the length of 72 Journal of Vector Ecology June, 1999 STAGE STAGE 2 STAGE 3 STAGE 4 PIeuron Tergum 45 Clockwise 45 Counter Clockwise Rotation Rotation Figure 1. Stages of rotation in the male tenninalia of Wyeomyia smithii. ovarian follicles, width of ovarian follicles, and length RESULTS of the follicles occupied by yolk using a one way ANOVA and Tukey's HSD test (Sokal and Rholf Immature Development 1981). Wyeomyia smithii eggs hatched on the fifth day after oviposition at 22+/-2C. Times spent in different Oviposition Cycles immature instars differed significantly (F =432.263; df We kept 50 newly emerged mosquitoes of each 4, 420; P < 0.001) and the mean duration of instars sex together in a 3.8 liter carton and isolated 30 differed significantly between sexes (F 432.263, df= females on the fourth day in individual glass vials 1,4; P < 0.001).