Oviposition Site Selection and Spatial Predictability of Female White-faced Dragonflies (Leucorrhinia intacta) (Odonata: Libellulidae)

Location of breeding or egg-laying sites may be an important factor underlying social behavior of many organisms. We studied oviposition sites used by a population of Leucorrhinia intacta dragonflies at a small pond near Syracuse, NY, USA. Females preferentially used shallow water as an oviposition habitat. Shallow water increases egg hatching rate through temperature effects on development time and reduces predation on the female. Use of shallow water areas was reduced by locally high densities of territorial males. The same oviposition sites probably maximized the fitness of the male, female, and offspring, meaning that site selection did not necessitate fitness tradeoffs among these classes of individuals. Pond sectors used by ovipositing females were significantly correlated within and between years, but not within days or between consecutive days. Use of pond sectors within and between days was not related to the relative availability of the shallow water habitat, while seasonal use of pond sectors was related positively to availability of shallow water. In spite of the preference by females for ovipositing in shallow water, short-term location of females was not predictable and males could not search predictably good areas during a day. However, across a season, areas with more shallow water available were used for oviposition more than areas with limited substrate.     

Cost of oviposition site selection in a water strider Aquarius paludum insularis: Egg mortality increases with oviposition depth

Females generally avoid selecting sites for oviposition which have a high predation risk to increase offspring survival. Previous studies have focused on costs to ovipositing females. However, although offspring may also incur costs by being oviposited at low predation risk sites, no studies have focused on costs to offspring. Such costs to offspring were examined by using Aquarius paludum insularis, females of which avoid eggs parasitism by ovipositing at deep sites. Deep sites are safe from egg parasitism but may be unsuitable for hatching due to environmental factors. We examined the costs to offspring at deep sites by comparing the hatching rate, the duration to hatching and the proportion of drowned larvae between eggs that were set at three levels of water depth (0 cm, 25 cm and 50 cm depth). While the hatching rate at 50 cm was lower than that at 0 cm, the rate at 25 cm did not differ from that at 0 cm. Duration to hatching and the proportion of drowned larvae did not differ between the three depths. It is suggested that the declining survival rate of A. paludum eggs was due to increased water pressure at greater depth. Such a cost may exist in other species and such an observation may aid in understanding oviposition site selection.     

Effect of body size and sugar meals on oviposition of the yellow fever mosquito,Aedes aegypti (Diptera: Culicidae)

The effects of dietary sugar and body size on the oviposition of Ae. aegypti were studied under laboratory conditions. In female mosquitoes provided with sugar, the start of maximum fecundity was significantly delayed and the oviposition period was longer than in females provided with water. The peak of oviposition was also delayed in sugar‐fed females. Large females oviposited more eggs per day than small females at maximum fecundity and during eight days of observations. Large females also visited significantly more water‐containing cups in their cages per day than small females at maximum fecundity. During the eight days of observations, large females and sugar‐fed females visited more water‐containing cups in their cages than water‐fed small females. Both large females and sugar‐fed females oviposited their eggs at sites higher above the water line than water‐fed small females. These results suggested that large and sugar‐fed female Ae. aegypti mosquitoes had more energy reserves and oviposited their eggs at higher sites, which would lead to a time lag in hatching.     

Breeding ecology and oviposition site selection of black-spotted pond frogs (Rana nigromaculata) in Ningbo, China

The black-spotted pond frog (Rana nigromacu-lata) is one of the most widely distributed species in China. However, there have been only a few qualitative descrip-tions of their breeding ecology and oviposition site selec-tion. From 2004 to 2006, we investigated the breeding ecology and oviposition site selection of K nigromaculata in Ningbo, China, quantitatively. Analyses of breeding ecology show that: (1) mean frog density in the breeding season was 0.0903 ± 0.0029 individuals per meter (n = 11) (mean ± SE); (2) R. nigromaculata was a sexually dimorphic species, with females significantly larger than males in both body weight and snout-vent length; (3) the clutch size averaged 4643.04± 235.96 eggs (range 1546-7897, n = 50); and (4) the egg size ranged from 1.50 to 1.74 mm in diameter, with an average egg size of 1.6050 ± 0.0046 mm (n = 226). Oviposition sites differed significantly from random sites in percentages of water, bare ground and vegetation cover, water depth (cm), water temperature (°C) and water turbidity. Rana nigro-maculata preferred microhabitats with higher percentages of water and vegetation cover, while it avoided microha-bitats with deeper water. The results suggest that micro-habitats with higher percentages of water and vegetation cover, but not deeper water, should be priorities for pro-tection and conservation of the breeding habitats of R. nigromaculata.     

Timing of oviposition and reproductive skew in cobreeding female burying beetles (Nicrophorus vespilloides)

Burying beetles (genus Nicrophorus) are known for their elaborate parental care. Two or more conspecific females may reproduceon the same carcass, especially when the carcass is large.Here we present the results of experiments in which we observedpatterns of larval hatching and parental care in unmanipulatedcobreeders, manipulated hatching synchrony between cobreeders,and compared patterns of oviposition in cobreeding and single females. Our results show that in these cobreeding associations,one of the females may or may not monopolize the carcass duringthe period of larval hatching. We present evidence that ineither case, infanticide based on temporal cues constitutesan important proximate mechanism underlying the observed reductionin average reproductive success in cobreeding females. Femaleswith higher synchrony (i.e., greater overlap between their oviposition patterns) produce larger broods with lower reproductive skew.Cobreeding females oviposit later and less synchronously thansingle breeders. Such delayed oviposition may reduce the riskthat a female's larvae fall victim to cannibalistic acts committedby her cobreeder or maximize her own opportunity to selectivelykill her cobreeder's larvae.     

Breeding strategy of the male brooding water bug,Diplonychus major esaki (Heteroptera: Belostomatidae): Is male back space limiting?

Breeding ecology of brooding males of the water bugDiplonychus major was investigated in the field and laboratory. During one breeding season an individual male may consecutively brood 3 or 4 egg-masses on his back until hatching. The 1st and the 2nd egg-masses brooded took about 1 month to hatch. Eggs generally hatched. Most of them hatched in synchronously, and males received a new brood of eggs within a few days. Therefore, total male back spaces in the pond, here regarded as the reproductive resource for females, showed considerable fluctuation. When the resource was in low availability, male back space was estimated to be strongly limiting, and in order to ensure successful oviposition in a competitive environment, females are expected to lay eggs aggressively. In laboratory studies, intensive competition to lay eggs was observed, and polygamy also occurred. Males always attempted to copulate before receiving eggs. However, some females sometimes thrust themselves into mating pairs and laid eggs without copulation before the copulating female laid her eggs. Repeated copulation was likely unnecessary for females. Furthermore, since individual male back space is always limiting for each individual male it is evolutionarily advantageous for a male to receive only eggs fertilized by himself. Oviposition occurring without additional copulations, as observed in this study, is new evidence supporting the paternity assurance hypothesis.     

Alternative oviposition behaviours in three New Zealand corduliid dragonflies: their adaptive significance and implications for male mating tactics

Oviposition behaviours of female, and mate acquisition and defence behaviours of male, 'Procordulia' grayi, Procordulia smithii and Hemicordulia australiae (three phylogenetically close corduliid species) are contrasted. Twelve distinct methods of oviposition occur involving different motor patterns. These different oviposition behaviours place ova into different microhabitats. Each species has a distinct repertoire of oviposition methods, with only one of the 12 methods occurring in more than one species. The oviposition behaviours differ in their susceptibility to male interference. The implications for male sperm displacement tactics and for the development of conditional male strategies are discussed. Male mating behaviour varies with the geometry of the breeding site, in a manner consistent with an ideal free distribution model where females vary in their 'value' through differential susceptibility to takeover by other males. It is shown that differential susceptibility of females to takeover would stabilize the observed mixed mating strategy among male 'P.' grayi and P. smithii .     

Effect of Population Density,Size of Habitat and Oviposition Substrate on the Breeding System of Pupfish (Cyprinodon pecosensis)

Size of habitat, availability of oviposition substrate, and population density were manipulated to determine their effects on the structure and dynamics of the pupfish breeding system. The fish established a territorial breeding system in large tanks, irrespective of population density or oviposition substrate. A dominance hierarchy, in which one male controlled most of the oviposition substrate and spawned with most females, was established in small tanks at low densities. Both population density and oviposition substrate affected the number of males defending territories. Male spawning success was inversely related to availability of oviposition substrate, but was not affected either by density or tank size. Location of a territory and its size also influenced spawning success. Males with bigger territories had higher spawning success. A “carryover” effect of neighbors was observed; males with reproductively active neighbors spawned more often than those with less successful neighbors. Interference with spawning was affected both by tank size and density. Agonistic behavior of breeding males was not affected by any manipulation, but it was positively associated with male spawning success at high but not at low densities. In all treatments the mortality of breeding males was approximately 8 times as high as that of females, suggesting that, under these experimental conditions, the cost of reproducing is substantially higher for males. Comparisons between breeding pupfish in these experiments and in natural environments provide a basis for understanding the selective pressures that have favored the maintenance of these extremely plastic breeding systems.     

Horizontal transfer of the insect growth regulator pyriproxyfen to larval microcosms by gravid Aedes albopictus and Ochlerotatus triseriatus mosquitoes in the laboratory

The insect growth regulator (IGR) pyriproxyfen is highly active against mosquitoes (Diptera: Culicidae). Through continuous emersion of large larvae (instars 3-4) the concentration causing 50% inhibition of adult emergence (EI50) was determined as 0.200 p.p.b. for Aedes albopictus (Skuse) and 3.5 to 7 times less for Ochlerotatus triseriatus (Say): IE50 0.0288 p.p.b. As a possible method of application to larval microcosms of these species that oviposit in water containers and phytotelmata, the horizontal transfer of pyriproxyfen to larval microcosms by adult mosquitoes was evaluated under laboratory conditions. Gravid females were forced to walk on surfaces treated with pyriproxyfen (tarsal contact exposure) and then allowed to oviposit in larval microcosms. Using replicate bioassay cages, each with an oviposition container, and a factorial experimental design, we assessed Ae. albopictus for the effects of (i) pyriproxyfen concentration (0.2, 0.3 and 0.4 mg/cm2) contacted by gravid females, and (ii) the number of treated gravid females added to bioassay cages (one, three or five females/cage), on the mortality of larvae in oviposition containers. Only 0.2 mg/cm2 treatment rate was tested on Oc. triseriatus. A significant (P < 0.05) curvilinear response in inhibition of emergence (IE) was achieved on both species. Densities of one or three treated Oc. triseriatus females/cage yielded IE rates of only 21-27%, whereas five treated females/cage resulted in 70% inhibition. With Ae. albopictus, densities of three or five treated females/cage yielded 48-67% and 59-73% IE, respectively, whereas one treated female/cage gave only 4-30% inhibition. Use of IGR-treated oviposition containers to achieve horizontal transfer of pyriproxyfen to mosquito oviposition sites could be a field management technique based on mosquito biology and behaviour. In binary choice tests with Ae. albopictus, horizontal transfer of pyriproxyfen from a container with a treated ovistrip (0.3 or 0.4 mg/cm2) to an untreated microcosm resulted in 14-38% inhibition. In larval bioassays, pyriproxyfen activity declined markedly within 10 days. Forcibly exposing gravid female mosquitoes to pyriproxyfen-treated paper surface did not affect their fecundity. However, from the 1st to 2nd gonotrophic cycles the egg hatch rate declined by 30% (P < 0.05). Some variation of results could be due to interactions between females at the oviposition site, possibly causing disproportionate transfer of pyriproxyfen to larval microcosms. Comparative studies of the oviposition behaviour of each mosquito are warranted and would potentially provide information needed to improve the technique.     

Laboratory and field evaluation of the effects of the neonicotinoid imidacloprid on the oviposition response of Aedes (Stegomyia) aegypti Linnaeus (Diptera: Culicidae)

In this paper, we assessed the suitability of using the neonicotinoid imidacloprid with standard ovitraps by evaluating the ovicidal properties of imidacloprid and its influence on the oviposition response of gravid females of Aedes (Stegomyia) aegypti Linnaeus (Diptera: Culicidae). First, we calculated the imidacloprid lethal dose 99 (LD(99)) by exposing third instar larvae of the target species to different concentrations of the insecticide. Next, Ae. aegypti eggs were exposed to the imidacloprid LD(99) for 24 h and hatching inhibition was recorded. Finally, we investigated any potential repellent effect of the imidacloprid solution on the oviposition response of gravid Aedes females in field and laboratory conditions. The LD(99) obtained from larvae tests proved to be sufficient to keep any exposed eggs from hatching. No repellent effect was observed; females laid as many eggs in imidacloprid-treated ovitraps as in traps containing either clean water or temephos-treated water in both field and laboratory conditions. Our results indicate that imidacloprid is a suitable insecticide for treating ovitraps against Ae. aegypti.     

Hydrologic and behavioral constraints on oviposition of stream insects: implications for adult dispersal

The supply of recruits plays an important role in plant and animal population dynamics, and may be governed by environmental and behavioral constraints on animals. Mated females of the mayfly genus Baetis alight on rocks protruding from streams, crawl under water and deposit a single egg mass under a rock. We surveyed oviposition and emergence of a bivoltine population of B. bicaudatus in multiple stream reaches in one high-altitude watershed in western Colorado over 3 years to establish qualitative patterns at a regional scale (entire watershed), and quantitative patterns over six generations at a local scale (one stream reach). We also measured characteristics of preferred oviposition substrates, performed experiments to test hypotheses about cues used by females to select oviposition sites, and measured mortality of egg masses in the field. Our goals were to determine whether: (1) hydrologic variation necessitated dispersal of females to find suitable oviposition sites; (2) the local supply of females could provide the supply of local recruits; and (3) local recruitment determined the local production of adults. The onset of oviposition corresponded with the decline of spring run-off, which differed dramatically among years and among sites within years. However, eggs appeared before any adults had emerged in 8 of 22 site-years, and adults emerged 2-3 weeks before any eggs were oviposited in 3 site-years. Furthermore, the size distribution of egg masses differed from that predicted by the size distribution of females that emerged from seven of nine stream reaches. Protruding rocks and eggs appeared earlier each summer in smaller tributaries than in larger mainstream reaches, suggesting that hydrologic and behavioral constraints on oviposition may force females to disperse away from their natal reach to oviposit, and possibly explain the predominantly upstream flight of Baetis females reported in other studies. Local oviposition rates in one third-order stream-reach increased rapidly as soon as substrates protruded from the water surface, and females preferred large rocks that became available early in the flight season. However, females oviposited on <10% of all available rocks, and <65% of preferred rocks as determined by an empirical model. These data indicated that the timing of appearance of suitable oviposition sites determined the phenology of local recruitment, but that preferred oviposition sites were not saturated. Thus, the magnitude of local recruitment was not limited by the absolute abundance of preferred oviposition sites. Only 22% of egg masses observed in the field suffered mortality during their embryonic development, and per capita Baetis egg mass mortality was significantly lower on rocks with higher densities of egg masses. Thus, we suspect that specialized oviposition behavior may reduce the probability of egg mortality, potentially compensating for the costs of dispersal necessary to locate suitable oviposition sites. Finally, the number of adults that emerged at one stream reach was independent of the number of egg masses oviposited over six generations of Baetis; and local recruitment was not a function of the number of adults of the previous generation that emerged locally. The patterns of oviposition and emergence of Baetis found in this study are consistent with the following hypotheses. Recruitment of eggs in a stream reach is not limited by the local supply of adults, but is a function of the regional supply of dispersing adults, which are constrained by the spatial and temporal distribution of preferred oviposition habitat. Furthermore, subsequent local production of adults is not a function of the supply of recruits, arguing for post-recruitment control of local populations by processes operating in the larval stage (e.g., predation, competition, dispersal, disturbance). Processes affecting larval and adult stages of Baetis act independently and at different scales, thereby decoupling local population dynamics of successive generations.     

Influence of breeding site availability on the oviposition behaviour of Aedes aegypti

Despite the importance of the mosquito Aedes aegypti in the transmission of arboviruses, such as yellow fever, Chikungunya fever and dengue fever, some aspects of their behaviour remain unknown. In the present study, the oviposition behaviour of Ae. aegypti females that were exposed to different densities of breeding sites (2, 4, 8 and 16) was evaluated in laboratory and semi-field conditions. The number of breeding sites that were used was proportional to the number available, but tended towards stabilisation. Females used four-six breeding sites on average, with a maximum of 11. A high percentage of eggs was observed in the water, along with the presence of a breeding site termed “favourite”, which received at least 40% of the eggs. The results are discussed in ecological, evolutionary and epidemiological approaches.     

Effects of pyriproxyfen and buprofezin on immature development and reproduction in the stable fly*

The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), is one of the most significant biting flies that affect cattle. The use of traditional insecticides for stable fly control has only a limited success owing to the insect's unique feeding behaviours and immature development sites. A laboratory study was conducted to evaluate the effects of two insect growth regulator (IGR) products, pyriproxyfen and buprofezin, on the development of the immature stages of the stable fly and the effects of pyriproxyfen on oviposition and egg hatch. Both pyriproxyfen and buprofezin had significant inhibitory effects on immature development. The LC₅₀s of pyriproxyfen and buprofezin were 0.002 and 18.92 p.p.m., respectively. Topical treatment of adult females with different doses of pyriproxyfen had significant negative effects on both female oviposition and egg hatching when 1‐ and 3‐day‐old females were treated, and the effects were dose dependent. A significant reduction in the mean number of eggs laid was observed only at the highest pyriproxyfen dose (8 µg/fly) and egg hatch was unaffected by pyriproxyfen treatment when 5‐day‐old females were treated. Results from the present study indicate that pyriproxyfen has the potential to be used as part of an integrated stable fly management programme.     

柳毒蛾繁殖生物学的初步观察

【目的】为了明确柳毒蛾Leucoma salicis(Linnaeus)交配的日节律高峰,温度和不同交配持续时间处理对成虫寿命、产卵量和孵化率等繁殖生物学的影响。【方法】将新羽化的柳毒蛾成虫置于养虫笼中,观察交配的日节律高峰,并统计不同温度和不同交配持续时间处理下的成虫寿命、产卵量和孵化率。【结果】成虫在羽化当晚的后半夜凌晨开始交尾,次日晚上开始产卵。成虫交配集中在羽化翌日凌晨3:00—5:00之间,高峰为4:00。产卵高峰都出现在2日龄成虫,但是,25℃下成虫交配持续时间(9.2 h)显著短于28℃(11.8 h)。交配持续时间为30、60和300 min的处理,雌成虫平均寿命显著长于对照(对照9.2 h),雄虫仅60 min的处理显著长于对照。同时,极短的交配持续时间(30 min)显著降低雌虫的产卵量和孵化率。【结论】试验明确了成虫交配的日节律高峰,在适宜的温度范围内(25~28℃),雌雄成虫的寿命、单雌总产卵量无显著差异,交配持续时间明显影响成虫寿命、产卵量和卵孵化率。     

Thermal preference in the pool frog Rana lessonae: impact on the reproductive behaviour of a northern fringe population

A documented warmth preference in the pool frog Rana lessonae is also expressed in the reproductive behaviour of a northern fringe population (60°N). During the breeding period of 31 days, individually marked frogs were observed during chorus. Male choruses were formed in the warmest parts of the pond, but moved between three areas. At night, these areas maintained the highest water temperatures in the pond, especially at low temperatures prevailing in the beginning of the breeding period. Oviposition occurred in the current chorus areas, and 86% took place during the first two weeks of the breeding period. That the choruses and oviposition changed locations within the favourable breeding areas can be explained by a pronounced thermal preference in the frogs, and winds moving the warm surface water in different directions.
The water temperature required to initiate oviposition was 16°C, which is similar to those reported from related more southern populations. The thermal preference expressed in the breeding behaviour of both sexes and the tendency for early oviposition may be behavioural responses to environmental constraints on reproduction in the short season at 6O°N.     

The reproductive biology of an armoured catfish,Loricaria uracantha,from Central America

Synopsis The reproductive biology of one of the poorly known armoured catfishes, Loricaria uracantha, was studied in Panama. Natural nesting sites consisted of cavities in pieces of wood, open at both ends and positioned above the stream bottom, but artificial cavities of PVC pipe were readily used. Males possess bony bristles on the head and pectoral fins which contact the female prior to oviposition. Males spawned with up to five females in short succession and remained with the eggs until hatching. Following hatching many initiated another spawning cycle. One male was reproductively active for 73 days during which it completed five distinct reproductive cycles. Spawning extended throughout the year.     

Alternative mate-finding tactics in a non-territorial damselfly (Odonata: Coenagrionidae)

Males of the non-territorial damselfly Enallagma hageni have two alternative tactics for finding mates: (1) they search the banks of the pond for unmated females (searching tactic), or (2) wait at oviposition sites for females that resurface prematurely from underwater oviposition (waiting tactic). Although the searching tactic yielded more fertilizations than the waiting tactic, for time invested, the waiting tactic became increasingly successful later in the reproductive season due to changes in female oviposition behaviour. The two tactics can be maintained in the population because males can mate by the waiting tactic during the afternoon when few females are available to searchers. Among males visiting the breeding site an equal number of times, males mating by a mixture of tactics were as successful as males mating only by the main tactic. Because marked males were found to use both tactics, these behaviours are interpreted as evidence of behavioural plasticity within individuals, representing one conditional evolutionary strategy.     

Effects of natal habitat odour, reinforced by adult experience, on choice of oviposition site in the mosquito Aedes aegypti

The effects of natal experience on the oviposition behaviour of adult female mosquitoes were investigated in the laboratory using Aedes aegypti (L.) (Diptera: Culicidae). 'Treatment' mosquitoes were exposed to a dilute repellent (inducing stimulus) in their breeding water (aquatic stages) and/or in the air (adults) during various combinations of life stages [larval only (L regime); larval and pupal (LP regime); larval, pupal and emergent adult (LPE regime); larval, pupal, emergent adult and adult (LPEA regime); pupal, emergent adult and adult (PEA regime); adult only (A regime)]. 'Control' mosquitoes were raised in an identical manner, but were not exposed to the inducing stimulus. The oviposition behaviour of treatment and control females was assessed in an oviposition assay that presented a choice of water with or without the inducing stimulus. Of the 435 mosquitoes tested in the experiment, 176 were non-distributors (i.e. laid all of their eggs in only one of the choices). Treatment females (distributors plus non-distributors) reared in the presence of the inducing stimulus throughout their lives (LPEA regime) showed a significant preference for the oviposition option containing the inducing stimulus (24/36 females) compared with corresponding controls (5/39 females). Distributors reared under the LPEA and PEA regimes also showed this preference (6/6 treatment vs. 2/29 control females, and 13/18 treatment vs. 7/23 control females, respectively). Females that had been exposed to the inducing stimulus as either immatures or adults only showed no preference for, and some showed an aversion to, the treatment oviposition option. This is interpreted as evidence for a natal habitat preference induction (NHPI) in this species, albeit one that requires extensive reinforcement in the adult stage. This adult experience-reinforced NHPI (AER-NHPI) is discussed in terms of its adaptive significance for container breeders, the possible timing mechanism and sensory basis of induction and potential practical consequences.     

Oviposition in three species of limnephiloid caddisflies (Trichoptera): hierarchical influences on site selection

1. Oviposition site selection was studied in three trichopteran species; an undescribed species of Hydatophylax (Limnephilidae), Onocosmoecus unicolor (Limnephilidae) and Neophylax rickeri (Uenoidae), in two Coastal Range streams in California, U.S.A. 2. Hydatophylax sp. egg masses were generally found at or above the water surface on substrata near the bank in pools, where undercut banks, overhanging vegetation and rocks shaded attachment sites and provided wind protection. Onocosmoecus unicolor females deposited their egg masses exclusively above the water on moist emergent wood. The egg masses of N. rickeri were almost exclusively found in high velocity areas of riffles, where females oviposited under water and attached their egg masses to the submersed undersides of unembedded, protruding stones with large emergent surfaces. 3. For Hydatophylax sp. and N. rickeri, a hierarchical selection scheme is proposed in which females use cues at three different spatial levels (stream, stream subunit, substratum) to choose oviposition sites. Females of O. unicolor seemed to choose at only two different levels of spatial resolution (stream, substratum). 4. The formation of large aggregations of egg masses in N. rickeri and O. unicolor suggests that females actively choose oviposition sites where conspecific egg masses are already attached. The clustering of egg masses may minimise the risk of predation through the dilution effect, because egg masses of N. rickeri and O. unicolor are both attacked by dipteran predators. 5. Females of the three Trichoptera species studied are able to make a clear choice of oviposition site in the heterogeneous stream environment. In comparison with other stream microhabitats, these are characterised by stable and relatively predictable environmental conditions during the time of egg development, which is seen as the main selective pressure leading to the observed egg‐laying behaviour.