Feeding and breeding aspects of Stomoxys calcitrans (Diptera: Muscidae) under laboratory conditions

Bionomic aspects of Stomoxys calcitrans (Linnaeus, 1758) (Diptera: Muscidae) were studied under laboratory conditions. For this reason, laboratory-rearing techniques were optimized at the National Veterinary School of Toulouse. The colony was maintained at 25 ± 2 °C, 50 ± 10% RH under a 12-hour light cycle and observed daily. The size of each adult cage is 30 x 30 x 30 cm and designed to house about 500-1,000 flies. The average cycle from egg to adult was 19.2 ± 1.7 days. The mean longevity of imagos was 9.3 ± 5.8 days and not significantly different between sexes. Stable flies were split into two groups; the first was fed with blood, honey and water, and the second was fed only with honey and water. The mean weight of a blood meal was 11.1 ± 3.8 mg with no significant differences between males and females. The mean longevity of non-blood fed flies was found to be significantly higher (10.4 ± 3.9 days) than those fed with blood. The maximum lifespan was shorter for non-blood fed males (17 days) and females (18 days) than for those fed with blood (females: 24 days, males: 23 days). Under these laboratory conditions, S. calcitrans rearing was successfully established. In the end, the number of expected generations of S. calcitrans and the net reproduction rate were estimated to be 11.8 generations/year and 16.2 living females per female respectively.     

Sex differences in phenotypic plasticity of a mechanism that controls body size: implications for sexual size dimorphism

The degree and/or direction of sexual size dimorphism (SSD) varies considerably among species and among populations within species. Although this variation is in part genetically based, much of it is probably due to the sexes exhibiting differences in body size plasticity. Here, we use the hawkmoth, Manduca sexta, to test the hypothesis that moths reared on different diet qualities and at different temperatures will exhibit sex-specific body size plasticity. In addition, we explore the proximate mechanisms that potentially create sex-specific plasticity by examining three physiological variables known to regulate body size in this insect: the growth rate, the critical weight (which measures the cessation of juvenile hormone secretion from the corpora allata) and the interval to cessation of growth (ICG; which measures the time interval between the critical weight and the secretion of the ecdysteroids that regulate pupation and metamorphosis). We found that peak larval mass of males and females did not exhibit sex-specific plasticity in response to diet or temperature. However, the sexes did exhibit sex-specific plasticity in the mechanism that controls size; males and females exhibited sex-specific plasticity in the growth rate and the critical weight in response to both diet and temperature, whereas the ICG only exhibited sex-specific plasticity in response to diet. Our results suggest it is important for the sexes to maintain the same degree of SSD across environments and that this is accomplished by the sexes exhibiting differential sensitivity of the physiological factors that determine body size to environmental variation.     

Changes in the titer of the female-predominant storage protein (81K) during larval and pupal development of the waxmoth,galleria mellonella

The levels of an 81K storage protein in the waxmoth, Galleria mellonella, were monitored during the course of development using rocket immunoelectrophoresis. During the fifth and sixth larval stadia, 81K protein levels increased during feeding and growth but sharply declined at each larval molt. During the fifth and sixth stadia hemolymph levels of the 81K protein increased to about 1 and 2.5 mg/ml, respectively, with no discernible differences between levels in males and females. Neither the fat body nor the remainder of the carcass contained the 81K protein, indicating that the accumulation of this protein during the intermolt period was exclusively in the hemolymph and redistribution of the 81K protein into other tissues does not occur at the final two larval molts. During the seventh (final) larval stadium the absolute quantities of the 81K protein increased from 23 μg per insect to over 1,600 μg in females and to 300 μg in males. The hemolymph concentration of the 81K protein reached 28 mg/ml in females and 6 mg/ml in males with only low levels found in the remaining tissues. Shortly after pupal apolysis, marked by eyespot retraction, the fat body in both sexes rapidly and quantitatively sequestered the 81K protein from the hemolymph. The 81K protein in the hemolymph of both males and females rapidly dropped to nearly zero concentration by pupation. The 81K storage protein remained localized in the fat body cells after uptake occurred, even though the fat body cells disaggregate and reaggregate during metamorphosis. During pharate adult development the 81K storage protein disappeared from the fat body without entering the hemolymph. At adult eclosion 81K was virtually absent from the tissues of both males and females.     

Nature and fate of the nutrient reserves of the periodical (17 year) cicada

The metabolic reserves of Magicicada cassini, a periodical cicada with a 17 year life cycle, were examined. Analysis of males and females which were collected shortly after emergence and just before death provided information about the nature and fate of the reserves which had been accumulated during the attenuated larval period. Results showed that young females had a mean weight of 565 mg compared with only 351 mg for equivalent males. Lipids and soluble proteins were the principal reserve materials. Glycogen was a relatively minor reserve of both sexes. While young females contained about twice as much soluble protein (110 mg) as the males (51 mg), they contained three times as much total lipid material (58–19 mg). Lipids were fractionated into neutral and phospholipids and the absolute amounts of each class were determined; triglycerides were the main component.Further analyses of old females provided information about the utilization of reserves for oögenesis. The data showed that even though the adults feed, lipids and soluble proteins stored during the larval stages are essential for egg maturation. The results are discussed in relation to the special requirements of an insect which has a protracted immature stage, yet a fleeting adult existence.     

Energy balance in Speliphron violaceum (Hymenoptera) and use of meconium weight as an index of bioenergetics components

Summary Speliphron violaceum deposits its larva and a few paralysed spiders inside the holes of electrical sockets. The larva feeds on the spiders, completes development in 6 days and emerges after 18 days of pupation. When provided with spiders to the maximum capacity of the hole, a larva consumed 1.746 KJ and converted 1.360 KJ. Restriction of the quantity of spiders provided, resulted in decreased consumption and extension of larval duration to 7 or 8 days. Consumption of 0.710·718 KJ was the minimum requirement for the completion of larval development. Despite variations in food consumption, assimilation efficiency of the larva remained constant around 97%. Gross production efficiency of the larvae averaged 77%. Larvae ingesting different amounts of host energy emerged with a wide range of body weight (16–62 mg). The efficiency with which pupal energy is transferred to adult was around 30%. Dry weight of meconium egested by the test individuals varied from 1.3 to 4.6 mg. Using simple regression equations, it is possible to predict the bioenergetics components of S. violaceum from the dry weight of meconium.     

Effects of larval density and food stress on life‐history traits of Cnaphalocrocis medinalis (Lepidoptera: Pyralidae)

High population density and nutrition restriction can lead to phase variation in morphology and development, and subsequently induce changes in the reaction norms of adult flight in migrant insects. However, response of migratory propensity to such stress in Endopterygote insects, especially in several species of Lepidoptera, remains unclear. In this study, larval and adult developmental responses to crowding and food stress were investigated in the migratory moth, Cnaphalocrocis medinalis (Guenée). A high larval rearing density significantly reduced pupal mass, survival rate and female fecundity. Larvae developed rapidly under crowding conditions, and time to pupation was 2 days earlier than individuals reared alone. By contrast, short‐term starvation and associated compensatory growth prolonged larval duration by 3–4 days and pupal duration by 1–2 days. It also reduced the pupal mass, but showed no detectable effects on female reproductive performance. Both sexes had similar development strategies; however, females seemed to be more sensitive to crowding and food shortage than males. A positive effect was expected if such stress factors acted as cues that triggering a behavioural or physiological shift to a distinct migratory phase. To the contrary, we found no proof that crowding and starvation caused maturation delay in female reproductive development. All treatments did not significantly increase female pre‐oviposition period. Therefore, we concluded that life developmental responses to crowding and food shortage in this species were different. Adult migration propensity was not enhanced under such stress conditions during the larval phase.     

Polygyny and the breeding success of the great reed warblerAcrocephalus arundinaceus

Settlement date, mating status, and breeding success of individually marked great reed warblers, Acrocephalus arundinaceus, were studied during the 1980–84 breeding seasons in Kahokugata, Ishikawa Prefecture, Japan. Twenty-five per cent of the territorial males were polygynous, of which the majority were bigamous. The settling periods of both sexes were long, extending for 65 days in males and 49 days in females. About 80% of males and females settled in the first half of the settling period, and the settlement date of 28–54% males overlapped with that of females. Many of the late settlers were bachelors and the males which mated earlier tended to be polygynous. The timing of a male's settlement is important in acquiring mates. Fifty-five per cent of eggs laid were lost before fledging, mainly due to predation. The mean number of fledglings was 3.19 per primary female, 2.41 per secondary female, and 2.80 per monogamous female. Comparison of the number of fledglings of females which mated during the same period showed that the presence of another female in the same territory did not adversely affect the breeding success of either of the polygynous females. Polygynous males have the advantage of decreasing the risk of breeding failure under high predation pressure.     

Contest competition inDrosophila subobscura

The role of larval intraspecific competition in laboratory populations ofDrosophila subobscura was investigated. Mortality is density-independent during the first 3 days after hatching but becomes density dependent as development proceeds to pupation. Although total biomass per patch was independent of initial egg density, competition betweenDrosophila larvae leads to the formation of smaller pupae. This resulted in a population that was dominated by suppressed individuals. Development rate ofD. subobscura larvae was not affected by high larval densities. Smaller pupae give rise to females with fewer eggs in their ovarioles. A simple simulation model, predicting the effects of intraspecific competition on the fecundity of the nextDrosophila generation is described.     

Male mate-locating behavior inEuphydryas chalcedona (Lepidoptera: Nymphalidae) related to pupation site preferences

Males of the checkerspot butterfly (Euphydryas chalcedona)patrol and perch near but not on the larval foodplant in search of females. Experiments with tethered butterflies show that searching males chase virgin females for longer times than they do mated females or males. The larvae leave the larval food-plant to pupate. The correspondence between the distance from the larval foodplant to pupation sites and where males search for females suggests that male mate-locating behavior has evolved to maximize the rate of encounters with newly emerged, virgin females. These conclusions are compared to a recent analysis of butterfly mating systems by Odendaal et al. (Am. Nat. 125: 673–678, 1985).     

Influence of dietary improvement on oviposition and egg viability of the mite, Tetranychus urticae

New formulations of a chemically defined diet on which Tetranychus urticae has been reared resulted in a pre-oviposition period being shortened from 3·5 to 1·5 days, an oviposition rate increased from 0·343 to 0·649 egg/female mite per day and an oviposition period extended from 25 to 36 days, and egg viability increased from 3·6 to 19·2 per cent hatchability. These formulations included deletion of cholesterol from the diet and inclusion of plant sterols only, a higher level of total sterols combined with a lower level of total fatty acids, and the addition of vitamin E (alpha tocopherol).     

Comparison of life history characteristics of the genetically modified OX513A line and a wild type strain of Aedes aegypti

The idea of implementing genetics-based insect control strategies modelled on the traditional SIT (Sterile Insect Technique), such as RIDL (Release of Insects carrying a Dominant Lethal), is becoming increasingly popular. In this paper, we compare a genetically modified line of Aedes aegypti carrying a tetracycline repressible, lethal positive feedback system (OX513A) with a genetically similar, unmodified counterpart and their respective responses to increasing larval rearing density using a constant amount of food per larva. The parameters that we examined were larval mortality, developmental rate (i.e., time to pupation), adult size and longevity. Analysis revealed some statistically significant differences between the life history traits we examined. The genetically modified OX513A line overall showed 5% lower larval survival as well as reduced adult longevity (20 vs 24 days mean lifespan) compared to the unmodified line. Furthermore, the OX513A line pupated about one day sooner, which could be advantageous in mass-rearing, but produced somewhat smaller adults than the unmodified line; this effect was more pronounced in females than in males. Increasing the larval rearing density delayed pupation, decreased adult longevity and reduced adult size in both lines. While the delay in pupation and the decrease in longevity were similar between the two lines, the decrease in adult size was more pronounced for OX513A males.Our study shows that in a controlled laboratory situation the transgenic sterile OX513A line may have somewhat reduced performance compared to its unmodified counterpart and that high rearing densities may further reduce performance. Laboratory-based cage trials as well as field trials are necessary to assess how the differences in life history traits documented here impact the males' success upon release. Furthermore, this paper highlights the potential value of optimisation of mass-rearing systems as optimised rearing methods may be able to alleviate performance issues associated with specific lines or with lab-adapted lines in general.     

In vitro rearing Oestrus caucasicus third-instar larvae and pupae (Diptera: Oestridae) from naturally-infested Iberian ibex, Capra Pyrenaica (Artiodactyla: Bovidae)

Third-instar Oestrus caucasicus larvae (n = 236) obtained from Iberian ibex, Copra pyrenaica, were reared in a laboratory to obtain adult flies. They were maintained at a temperature of 21.9 +/- 2.7 degrees C and a relative humidity of 38.9 +/- 8.0 %. In all, 78 imagos emerged (33.1 %), with a sex-ratio at emergence not differing significantly from 1:1; 25 larvae did not complete pupariation. A total of 14 adult flies (17.9 % of the adults obtained) showed malformations, mainly in their wings. The pupariation period lasted around 30 hours and the pupal stage lasted on average 29.8 +/- 6.8 days. The success of pupation in both sexes was mainly determined by the weight of the larvae. Sexual dimorphism, with higher weights in females, was evident in third-instar arvae, pupae and adults. The mean longevity of adult flies was 224.8 +/- 91.4 hours and males generally survived for onger than the females.     

Population structure of the rare damselfly,Ischnura gemina (Kennedy) (Odonata: Coenagrionidae)

Summary The population structure of the endemic San Francisco Bay Area damselfly, Ischnura gemina, is examined using mark-recapture methods. Average daily movements, sex ratios, population size, maturation times, survivorship, and dispersion patterns, were recorded and calculated from two small (each less than one hectare) sites 150 m apart in Glen Canyon, San Francisco. Of 563 adults marked over 36 days, 412 (73%) were recaptured at least once. Average daily movements for males and females were less than 6 m, suggesting local movements. However, directional movements of 150 m were observed from one site to the other, indicating dispersal potential. One of the populations was a satellite composed entirely, of emigrating individuals from the other site; no larvae or teneral adults were found at the satellite area. Males were more aggregated than females at both sites. Both sexes were highly clumped at one site but were nearly randomly dispersed at the other site. Total population size for both sexes tended to be constant throughout the sampling period, at about 250. Adult population estimates showed more males were present than, females, but larval counts at one site indicated only a slight excess of males. Average life span estimates ranged from 6.5 days (females) to 23.3 days (males). One male lived at least 36 days. Maturation time for males was about 5–7 days, 7–10 days for females. A long life span and long flight season (March to November) are probably adaptations to the foggy San Francisco climate. All populations of I. gemina located to date are small, possibly originating from founders from nearby demes, and may be subject to different selection pressures. The dispersal potential of I. gemina may increase its chance of survival should small urban demes be threatened with destruction.     

The effect of host stage and temperature on selected developmental parameters of the solitary endoparasitoid Meteorus gyrator (Thun.) (Hym., Braconidae)

Abstract:  The development of the solitary endoparasitoid Meteorus gyrator was compared in the six larval stages of its host, the tomato moth Lacanobia oleracea , and at five constant temperatures. The host instar at the time of parasitism had a marked effect on the larval developmental period of the parasitoid, such that larvae derived from eggs oviposited in first instar hosts took approximately 18 days to egress, whilst those derived from eggs oviposited in sixth instar hosts took <10 days. The weight of cocoons was greatest when oviposition was into final instar hosts, where female cocoons averaged 12.8 mg, and lowest in those derived from eggs oviposited into first instars (9.2 mg). The parasitoid's larval development rate in third instar hosts increased with temperature increments in a linear fashion up to 25°C , after which development times were only marginally increased. At 10°C, the mean larval development time was approximately 90 days and pupal development 35–40 days, whilst at 25°C development times were 10–11 days for larvae and 6–7 days for the pupae. In the majority of cases, overall development times were marginally longer (<1 day) in females than in males.     

Simultaneous determination of molting and juvenile hormone titers of the greater wax moth

A simple and rapid extraction procedure was developed to determine simultaneously the molting hormone (MH) and juvenile hormone (JH) activity in a single insect tissue sample. From the onset of the last larval stage to adult eclosion of the greater wax moth, Galleria mellonella, three JH peaks were noted: at the time of the sixth larval ecdysis, 1 day before the seventh larval ecdysis, and at the time of adult eclosion. Three MH peaks were recorded for the male: at 1 day before the sixth larval ecdysis, 1 day before the seventh larval ecdysis, and 2 days after pupation. In the female, a fourth peak was shown at the time of adult eclosion. This fourth peak exhibits the highest molting hormone activity of all samples, 1600 Musca units/g of fresh tissue or an equivalent of 5.6 μg/g of ecdysterone. Eighty per cent of this MH accumulated in the ovary. The significance of MH and JH titers as related to the endocrine regulation of development is discussed in the light of this finding.     

Some factors affecting flight in field populations of the Australian plague locust, Chortoicetes terminifera (walker), in New South Wales

An attempt was made to determine some of the factors regulating flight activity in the Australian plague locust, Chortoicetes terminifera (Walk.) by comparing the physiological characteristics of flying and non-flying locusts at different times of the day. Flight during the day did not appear to involve extensive displacements of the insects and was dependent largely on the, environmental conditions. The physiological state and age did not seem important and the milling flight of swarms involved insects of all ages and states of sexual maturity and the insects were commonly fully fed. There was probably at this time a continual interchange of insects between the air and the ground provided wind speeds are not too high and the air temperature was not below 19°C. Night flight, however, was observed only in locusts after the teneral period, when cuticle deposition was nearing completion around 10 days after the imaginal ecdysis and, in the case of the females, the oocytes were relatively undeveloped. Night flight was also associated with a failure to feed prior to sunset; only those with empty foreguts being stimulated to fly with the drop in light intensity, when the temperature was not too low and certainly not below 17·5°C. It is probably the older insects which take-off in these circumstances for by the time of sunset 30 to 40 per cent of the older, ones apparently fail to feed on any one evening and empty locusts tend to be more active than fully fed ones. The females appeared to show a flight periodicity related to the oviposition cycle, which under suitable conditions, leads to the displacement of about one-third of the population which is sexually immature or which has already recently oviposited. The flight activity of females is probably greater than that of the males for the sexes were in equal ratio in insects caught in flight while males exceeded females in ground populations. At sunset, fewer females than males still had full foreguts and were perhaps more likely to take-off while a higher proportion of younger females than males may soon re-alight if their physiological state is unfavourable for prolonged flight at night.     

An Appraisal of Life History Features of Kiefferulus calligaster (Kieffer, 1911) (Diptera: Chironomidae) from Kolkata,India

Life history parameters of the freshwater chironomid species Kiefferulus calligaster (Kieffer, 1911) were investigated under laboratory conditions, with the use of larval development time and wing length as key features. An index of fitness was derived using these two parameters to represent the fitness of adults as a function of the larval development. Survivorship, deduced from the data on the mortality of larval stages, was related to developmental time as—(survivorship, l_x) y = 1.16 ? 0.04 × (days). The larval development time varied between males and females with a minimum of 8 and a maximum of 12 days from first instar larva to eclosion of imagine. The average wing length of adult females was larger than males (3.9 mm ± 0.03 S.E. vs. 3.36 mm ± 0.02 S.E.), for both early and late emerging individuals. The degree of dimorphism between the sexes was prominent for wing length and larval development time. The index of fitness for the early and late emerging adults differed significantly (P < 0.05) in both the sexes.     

Effects of high density on spacing behaviour and reproduction in Akodon azarae: A fencing experiment

We studied the short term spacing behavioural responses of Pampean grassland mouse (Akodon azarae) with regard to population density in four 0.25 ha enclosures (two control and two experimental) in the 2011 breeding season. Based on the hypothesis that A. azarae breeding females exhibit spacing behaviour, and breeding males show a fusion spatial response, we tested the following predictions: (1) home range size and intrasexual overlap degree of females are independent of population density values; (2) at high population density, home range size of males decreases and the intrasexual home range overlap degree increases. To determine if female reproductive success decreases at high population density, we analyzed pregnancy rate, size and weight of litters, and period until fecundation in both low and high enclosure population density. We found that both males and females varied their home range size in relation to population density. Although male home ranges were always bigger than those of females in populations with high density, home range sizes of both sexes decreased. Females kept exclusive home ranges independent of density values meanwhile males decreased home range overlap in high breeding density populations. Although females produced litters of similar size in both treatments, weight of litter, pregnant rate and period until fecundation varied in relation to population density. Our results did not support the hypothesis that at high density females of A. azarae exhibit spacing behaviour neither that males exhibit a fusion spatial response.     

Reproductive ecology of Odontostilbe pequira (Steindachner, 1882) (Characidae, Cheirodontinae) in the Paraguay River, southern Pantanal, Brazil

The reproductive biology of Odontostilbe pequira was studied aiming to determining differences in population structure, reproductive tactics and correlating the reproductive period with rainfall, temperature and level of the Paraguay River, in the southern Pantanal, Brazil. Data were obtained for 623 individuals (366 females and 257 males), and of these, 253 females and 126 males were dissected for reproductive analysis. No significant variation was observed in the distribution of standard length and total weight between the sexes. The sex ratio was 1.42:1 (female: male), but the ratio did not differ over most months and between most length classes. The reproductive period was long (10 months). No correlation was found between the gonadosomatic index (GSI) of both sexes with water temperature and rainfall over the months analyzed. Males showed no significant association between the GSI and river level, but a marginally significant correlation was observed for females. Moreover, an effect of the mean historical river level on GSI was observed in both sexes, indicating that the flooding regime drive the reproductive activity, which proportions spawnings even when rainfall and temperature levels are low. Length at first maturity of the females was 24.2 mm and of the males 22.2 mm, with a significant difference between the sexes. The mean absolute fecundity was 181.4 oocytes/female, while mean relative fecundity was 0.544 oocytes/mg. Absolute fecundity was positively related to total weight, gonad weight and standard length. The mean diameter of the mature oocytes was 0.46 mm and the frequency distribution of the diameters showed various modes, indicating a multiple spawning. Thus, the reproductive tactics of O. pequira was characterized as “opportunistic strategist”, with reproductive activity strongly associated with the flood pulse.     

Negative density-dependent emigration of males in an increasing red deer population

In species with polygynous mating systems, females are regarded as food-limited, while males are limited by access to mates. When local density increases, forage availability declines, while mate access for males may increase due to an increasingly female-biased sex ratio. Density dependence in emigration rates may consequently differ between sexes. Here, we investigate emigration using mark-recovery data from 468 young red deer Cervus elaphus marked in Snillfjord, Norway over a 20-year period when the population size has increased sixfold. We demonstrate a strong negative density-dependent emigration rate in males, while female emigration rates were lower and independent of density. Emigrating males leaving the natal range settled in areas with lower density than expected by chance. Dispersing males moved 42 per cent longer at high density in 1997 (37 km) than at low density in 1977 (26 km), possibly caused by increasing saturation of deer in areas surrounding the marking sites. Our study highlights that pattern of density dependence in dispersal rates may differ markedly between sexes in highly polygynous species. Contrasting patterns reported in small-scale studies are suggestive that spatial scale of density variation may affect the pattern of temporal density dependence in emigration rates and distances.