Effects of meadow suitability on female behaviour in the alpine butterfly Parnassius smintheus

Abstract  1. Many butterfly populations persist in networks of naturally fragmented habitat patches. Movement and reproductive decisions made by adult females are critical to the persistence of these populations because colonisation of extinct habitat patches in the network requires emigration of fecund adult females from their natal meadow and their subsequent establishment in the extinct patch.
2. Movement and oviposition behaviours of mated Parnassius smintheus females released in suitable meadows (a good- and a poor-quality meadow) and an unsuitable meadow were compared, to determine whether adult females consider meadow suitability for their offspring despite frequent oviposition events off the larval host plant.
3. Bootstrap and correlated random walk analyses of female step lengths and turn angles demonstrated that females flew more randomly in the unsuitable meadow than in the suitable meadows. Although females tended to turn the sharpest angle between landing sites in the good-quality meadow, and fly the smallest distance between landing sites and displace the smallest distance from the release site in the suitable meadows, no significant differences were detected in turn angle, step length, and dispersal rates between suitable and unsuitable meadows.
4. Results from female flight observations and a caged oviposition study suggest that females lay significantly more eggs in suitable habitat than in unsuitable habitat despite not ovipositing on the host plant, and support the above findings.
5. Movement and oviposition behaviours of adult female P. smintheus promote their retention within meadows that can support their offspring.     

Abundance,size, and feeding success of larval shortnose suckers and Lost River suckers from different habitats of the littoral zone of Upper Klamath Lake

We examined near-shore habitat use by larval shortnose and Lost River suckers in the lower Williamson River and Upper Klamath Lake of south-central Oregon. Emergent macrophytes Scirpus, Sparganium and Polygonum supported significantly more, larger, and better-fed larvae than submergent macrophytes, woody vegetation, or open water. Abundance, size, and gut fullness were similar for sucker larvae collected from different emergent macropytes. During the larval period, there was no evidence of density dependant effects or habitat shifts. Ranked catch per unit effort data indicated potential predators also were more likely to use emergent macrophytes, but ordination indicated larvae and potential predators were differentially distributed along a vegetation structure-water depth gradient with larvae in shallow vegetated areas. Between-habitat differences appeared to be due to larval sucker selection for, or better survival in, emergent macrophytes, rather than differential access or exclusion from other habitats. The importance of emergent macrophytes appears to be related to increased foraging success and reduced predation. Because larvae in emergent macrophytes have a size and gut fullness advantage, the amount of emergent habitat could affect early survival. However, interannual differences in recruitment to the adult population may or may not be dependent on larval dynamics. Our results suggest larval sucker access to emergent macrophytes may be necessary, but perhaps not sufficient, for promoting good year class formation.     

Metapopulation dynamics of the bog fritillary butterfly: movements between habitat patches

Recent studies on metapopulation dynamics have emphasized the need for improved methods for quantifying individual movements between local populations and habitat patches. In this paper, we report on a 6-yr study in which a network of 12 habitat patches occupied by the bog fritillary, Proclossiana eunomia , was surveyed, with special focus on quantifying movements between the habitat patches. We applied the Virtual Migration model which has been designed to estimate survival and migration parameters in a metapopulation of several connected local populations. The model was parameterized using mark-release-recapture data collected during 6 yr. Generally, the estimated parameter values indicated a high level of movements, with roughly half of butterfly-days spent outside the natal patch. Mortality within patches was higher in males than in females. Females tended to be more mobile and spent more time outside their natal patch than males. Further analysis of the MRR data shows that in this protandrous species males tend to move very little between habitat patches before substantial numbers of females have emerged.     

The effect of host size on quality attributes of the egg parasitoid,Trichogramma pretiosum

In a study of the quality ofTrichogramma pretiosum Riley (Hymenoptera: Trichogrammidae), we compared female wasps emerging from natural hosts, parasitized in the laboratory or the field with those emerging from factitious hosts used for commercial mass production. Females from the natural hosts were larger, more fecund, and longer lived than those from the factitious hosts. Compared to small females, large female wasps are substantially more fecund when honey (carbohydrate) is available but marginally more fecund when honey is unavailable. The size of a femaleT. pretiosum depends on two factors: the size of the host egg from which it emerges even when the wasp was gregarious, and the number of conspecifics that emerge with it. The similarities in the size distribution of female wasps emerging from natural hosts, in conjunction with the mechanism by whichTrichogramma measure host size and allocate eggs accordingly, suggests the hypothesis that size related components of fitness in femaleT. pretiosum are under strong selection in the field.     

A comparison of the developmental and reproductive biology of two soybean pod borers, Etiella spp. in Indonesia

Experiments conducted in West Java, Indonesia investigated the developmental biology and reproductive behavior of two sympatric soybean pod borers, Etiella zinckenella Treitschke and E. hobsoni Butler (Lepidoptera: Pyralidae). It was determined that: (1) significant interspecific differences occurred between the egg, larval, pupal and total egg-to-adult developmental periods of laboratory raised E. zinckenella and E. hobsoni; (2) the pre-pupal and total egg-to-adult development periods of female E. zinckenella were significantly shorter than for males; (3) the longevity of virgin female E. zinckenella was significantly longer than that of virgin males, or virgin male and female E. hobsoni; (4) interspecific differences occurred in the female: male sex-ratios of laboratory raised adults; (5) peak mating for both species occurred on the second night after eclosion; (6) interspecific differences occurred in the temporal distribution of calling and mating behaviors; (7) repeated mating was observed for both species at a very low frequency; (8) interspecific mating did not occur; (9) female E. zinckenella were significantly more fecund than E. hobsoni; (10) the duration in copulo of E. zinckenella was significantly longer than that of E. hobsoni; and (11) wingtraps baited with virgin females caught only conspecific males, and reduced numbers of males were captured in traps simultaneously baited with virgin females of both species. This study demonstrates distinct biological differences and reproductive isolation between the two Etiella spp.     

Pre- and post-maturation survival in adults of the damselfly Pyrrhosoma nymphula (Zygoptera: Coenagrionidae)

The technique of mark-release-recapture was used to study survival before and after sexual maturity in adults of the damselfly Pyrrhosoma nymphula (Sulzer). Fewer females were recaptured upon return to water to breed despite no differences in dispersal or daily survival rate between the sexes over the immature period. Because females took longer to mature than males, their poorer recapture rate was attributed to greater overall mortality during their longer maturation phase. Survivorship curves for tenerals marked at emergence suggested that overall survival of immature adults was similar to, if not better than, that of mature adults. The reasons for this are discussed.
Jolly's model was used to estimate daily survival rates for mature adults. The assumptions of the model were tested rigorously. Estimates for females were statistically less reliable than those for males. Mean reproductive spans for males and females were 6.8 and 6.6 days, respectively, giving mean total adult lifespans of 19.4 days and 21.6 days for individuals surviving the maturation period.
Because neither sex visited the breeding site every day, sampling exclusively at water resulted in underestimation of mean reproductive spans for both sexes. Female reproductive spans were underestimated to a greater extent; because females remain away from water longer between visits, there is a greater chance that they will die before being recaptured.
Mean reproductive spans were also underestimated when only a sub-section of the habitat was sampled. Females were significantly more mobile than males and this increased the likelihood that they would move out of the study area, resulting in more severe underestimation. The importance of obtaining accurate estimates of mature lifespan for females is discussed.     

Host location by chemical stimuli in Bracon hylobii (Ratzeburg) (Hymenoptera: Braconidae), a larval parasitoid of Hylobius abietis (L.) (Coleoptera: Curculionidae)

The Large Pine Weevil, Hylobius abietis, is one of the most important pests in European coniferous forests. The ectoparasitoid Bracon hylobii is known to cause around 50% larval mortality. Chemical volatiles are among the most important stimuli involved in the host location. In the present study, a 4-arm olfactometer and a 2-choice wind-tunnel were used to test the behavioural responses of B. hylobii females to four odour sources from the host-plant/host-insect complex. For each odour, the behaviour of twenty virgin females was individually recorded in an olfactometer, whereas twenty virgin and twenty mated females were individually tested in a wind-tunnel. The following behavioural parameters were analysed: a) time spent walking; b) time spent stopped; c) total time spent in each arm; d) total speed; e) net speed; f) the rate of turning per unit distance walked; g) rate of turning per second. Comparison between odours shows clear differences in the behavioural parameters analysed. In particular, the bark disc/larva complex is the only odour source able to elicit behavioural responses of both naive and mated females. As strong responses were obtained only using experienced females, this suggests that previous searching activities increase the ability of B. hylobii to find its host.     

Olfactory Responses by the Scale Insect Predator Chilocorus nigritus (F.) (Coleoptera: Coccinellidae)

Orientation to host plant and host insect volatiles in the coccidophagous coccinellid, Chilocorus nigritus (F.) was examined using a four-arm olfactometer. Experienced adult females were attracted towards the combination of Solanum tuberosum L. and Abgrallaspis cyanophylli (Sign.) odours, walked further and spent longer in their presence, and showed an increased turning rate and net speed than in their absence. Host plant volatiles increased speed but decreased turning rates compared with odourless controls, but elicited no strongly directional response. It is postulated that this beetle and other coccinellids have a hierarchical prey-location mechanism which involves host habitat location based on olfactory responses.     

Experimental Evidence for Male Sequential Mate Preference in a Lekking Species

In lekking species females visit male aggregations solely to copulate or have their eggs fertilized. Because lekking males do not contribute to parental care, evolutionary theory does not expect them to be choosy. However, we show here that in the cichlid fish Astatotilapia flaviijosephi the lekking males exhibit sequential mate preference that strongly suggests a trade‐off between present and future reproductive effort. We tested mate preferences of A. flaviijosephi males by sequentially presenting them with two images of a gravid female, differing only in size. Previously, males were shown to prefer larger, more fecund females in simultaneous preference tests. The sequential presentation experiment reported here indicates that even in the absence of simultaneous presentation, males spent more time courting larger female images, and stayed longer in their vicinity. Thus, our study suggests that lekking males may be much choosier than previously appreciated. Furthermore, considering the intense competition among lekking males we also suggest that male choosiness, combined with other factors, may help to solve the ‘paradox of the lek’. It can make less attractive females more available to subordinate males, thereby increasing the contribution of the latter to the population gene pool and keeping genetic variability among males at a level that justifies female choice.     

Polyphagy and primary host plants: oviposition preference versus larval performance in the lepidopteran pest Helicoverpa armigera

Oviposition preference and several measures of offspring performance of Helicoverpa armigera (Hübner) were investigated on a subset of its host plants that were selected for their reputed importance in the field in Australia. They included cotton, pigeon pea, sweet corn, mungbean, bean and common sowthistle. Plants were at their flowering stage when presented to gravid female moths. Flowering pigeon pea evoked far more oviposition than did the other plant species and was the most preferred plant for neonate larval feeding. It also supported development of the most robust larvae and pupae, and these produced the most fecund moths. Common sowthistle and cotton were equally suitable to pigeon pea for larval development, but these two species received far fewer H. armigera eggs than did pigeon pea. Mungbean also received relatively few eggs, but it did support intermediate measures of larval growth and survival. Fewest eggs were laid on bean and it was also the least beneficial in terms of larval growth. Among the host plant species tested, only flowering pigeon pea supported a good relationship between oviposition preference of H. armigera and its subsequent offspring performance. Australian H. armigera moths are thus consistent with Indian H. armigera moths in their ovipositional behaviour and larval performance relative to pigeon pea. The results suggest that the host recognition and acceptance behaviour of this species is fixed across its geographical distribution and they support the theory that pigeon pea might be one of the primary host plants of this insect. These insights, together with published results on the sensory responses of the females to volatiles derived from the different host plant species tested here, help to explain why some plant species are primary targets for the ovipositing moths whereas others are only secondary targets of this polyphagous pest, which has a notoriously broad host range. Handling Editor: Joseph Dickens     

Visual Evaluation and Recognition of Hosts by the Tick Parasitoid, Ixodiphagus hookeri (Hymenoptera: Encyrtidae)

The role of host size, movement, feeding status, color, and species in the visual host evaluation and recognition behavior of the tick parasitoid, Ixodiphagus hookeri Howard was investigated. Freshly emerged female parasitoids were subjected to a choice bioassay, where the test materials were placed in sealed vials and the vials placed in a Petri dish. When presented with A. variegatum live and mummified nymphs, females examined: larger nymphs significantly longer than smaller nymphs, fed nymphs significantly longer than unfed nymphs, dead and live nymphs for similar lengths of time, and grey live nymphs and yellow-brown and dark brown mummified nymphs for similar lengths of time. The total number of visits to vials containing these test materials were also not significantly different, except there were significantly more visits to yellow-brown mummies when compared to the number of visits to dark brown mummies. When presented with A. variegatum (host) and R. appendiculatus (nonhost) nymphs, the females examined A. variegatum nymphs significantly longer than R. appendiculatus nymphs. The total number of visits to vials containing A. variegatum nymphs were significantly more than the visits to the vials containing R. appendicualtus nymphs. Furthermore, females spent significantly more total examination time per visit on larger and fed A. variegatum nymphs when compared to smaller and unfed nymphs, respectively. Direct and indirect detection were significant when females were presented with fed versus unfed A. variegatum nymphs, grey nymphs versus yellow-brown mummies, and R. appendiculatus versus A. variegatum nymphs. Direct and indirect detection for the rest of the bioassays were not significantly different. Finally, The percentages of females contacting large fed A. variegatum nymphs first were significantly different from those of females contacting small unfed R. appendiculatus nymphs first. The firstcontact percentages for the rest of the bioassays were not significantly different.     

In Vitro Rearing of the Parasitoid Exorista larvarum (L.) (Diptera: Tachinidae) on Meat Homogenate-Based Diets

The tachinid Exorista larvarum (L.), a polyphagous gregarious larval endoparasitoid of Lepidoptera, was reared from egg to fecund adult on media containing commercial meat homogenates for babies as the main ingredient. Four media, each containing a diverse homogenate supplemented with extract of Galleria mellonella L. pupae, were tested first. Despite the difference in nutrient content, the kind of homogenate did not significantly affect the adult yields (30.2 to 40.7%) or puparial weights. Two other diets free of host materials (I and II) were then tested. Both were based on Gerber veal homogenate combined with different amounts of yeast extract and chicken egg yolk and were supplemented with wheat germ (I) or saccharose (II). Adult yields (28.7 to 32.7%) and puparial weights did not differ significantly between the two diets. Fly longevity and fecundity of the females obtained on diet I were comparable to those of the females emerged from puparia formed in G. mellonella larvae. Male and female puparial weights were, however, higher and development times longer on the diet than in the host.     

Hunting for moving hosts: Cephalonomia tarsalis, a parasitoid of free-living grain beetles

The parasitic wasp Cephalonomia tarsalis parasitizes larvae of the saw-toothed grain beetle Oryzaephilus surinamensis, which feed on wheat grains. In contrast to most other host–parasitoid systems studied so far, the grain beetles are highly mobile within their habitat, bulk of grains in grain stores. This should increase the wasps’ problem to locate the hosts. To study the host-finding strategy of C. tarsalis females, the reaction of wasps to different grain and host-derived odour sources was tested in a four-chamber-olfactometer. These experiments revealed that wasps were attracted by healthy grains and mechanically damaged grains. In direct comparison, healthy and mechanically damaged grains are equally attractive. Both potential sources of host-derived odours, host faeces and trail-traces of larvae on filter paper were attractive to the wasps. The response to trail-traces vanished 30 min after larvae had been removed from the filter paper. With respect to the specificity of the odours, it turned out that wasps were attracted to odours from the seed–host complexes from O. surinamensis and Oryzaephilus mercator and the non-host complex of larvae of the granary weevil Sitophilus granarius in wheat grains. Odours from the seed–host complex were preferred. From these results, we hypothesize that host habitat location in C. tarsalis is achieved by using grain-derived odours. Within the habitat, wasps search for kairomones from host faeces and host trails. Following these larval trails finally leads wasps to their hosts.     

Nitrogen fixation by intact colonies of the termite Nasutitermes corniger

Summary Biosteres longicaudatus Ashmead (Hymenoptera: Bracon dae) is a solitary endoparasite of Anastrepha suspensa larvae (Diptera: Tephritidae), which live in fruit tissue. Larvae make andible noises within macerated fruit or larval medium in which they are reared. Parasite females readily located normal, mobile larvae and spent a mean of 16.5±4.7 min/visit to parasitize these hosts. In contrast, females were unable to locate etherized or dead hosts and abandoned them after only 1.9±0.9 and 2.3±0.8 min, respectively. Females of all ages, with and without oviposition experience, exhibited non-random search and ovipositor probe behaviors in response to artifically created vibration. This response was influenced primarily by the number of mature eggs in the ovaries. These findings suggest that 1) an accumulation of mature eggs in the ovaries increase the appetitive drive of females to find and oviposit in hosts and 2) host sound/vibration produced either by movement of hosts through the medium and/or by the rasping mouth hooks during feeding. is used by parasites as a releaser for host finding behavior as well as a cue to the location of the host within the substrate.     

Parental care behavior in the monogamous,sexually dimorphic Madagascar paradise flycatcher: sex differences and the effect of brood size

I studied the parental care behavior of the Madagascar paradise flycatcher Terpsiphone mutata in northwestern Madagascar. I especially focused on feeding, brooding and vigilance behaviors. Feeding rate did not differ between males and females, but females spent more time at the nest than males. Females dedicated their time to brooding, while males perched on the nest and were vigilant. Both parents changed the feeding rate in relation to brood size, so the feeding rate per nestling was not different among nests of different brood size. Duration of brooding by females increased with decreasing brood size, suggesting that the Royama effect, the pattern of lower feeding rate per nestling in larger broods, did not apply in this study. Males spent more time on vigilance than females. Anti-predator vigilance by males should be important for nestling survival given the high predation pressure typical of this population. In conclusion, males provide considerable parental care probably to minimize nestling starvation and to avoid nest predation. My results are not consistent with the general pattern of less parental effort by males in monogamous, sexually dimorphic species.     

Microhabitat selection by larval Chironomus tentans (Diptera: Chironomidae): effects of predators, food, cover and light

1. As part of a study designed to estimate the developmental costs of antipredator behaviour of larval chironomids, we used laboratory experiments to study effects of food and factors that could influence predation risk [presence of fish, cover from fish (simulated debris) and light level], on microhabitat selection by Chironomus tentans larvae in the third and fourth instar. 2. Larvae were more likely to build tubes where there was more food although their ability to move far to find food appeared limited. 3. Larvae did not avoid areas with fish and the presence of fish did not alter larval response to food. 4. Larvae avoided areas of cover (simulated debris) but cover did not alter larval response to food. 5. When provided with a choice between light and dark areas, larvae initially without tubes were found more often in the dark areas. Light level had no effect on location of larvae that had begun the experiment with tubes. 6. Results suggest the tubicolous life-style of larval Chironomus tentans limits their ability to select microhabitats that could alter their risk of predation.     

Aspects of the biology of the catfish Clarias lazera (Cuv. & Val.) related to its economic cultivation

The seasonal abundance, population structure, reproduction, feeding, respiratory adaptations and tolerance were studied in the catfish Clarias lazera (Cuv. & Val.) in the reservoir of Jebel Aulia on the White Nile, and in the Green-Belt canals near Khartoum. Continuous monitoring of the ripe, spent and spawning females and immature fish in the population revealed that C. lazera breed synchronously in the autumn in the reservoir and rather sporadically in the canals. Medium-sized females were more fecund than old and young females. Administration of pituitary extract enhanced maturation, induced spawning in mature fish, stimulated body growth, especially in maturing specimens, and produced, as a side-effect, a diuretic response. Mature fish depended on pulmonary respiration for about 45% of the total oxygen requirement. C. lazera fed preferentially on its fry and on decayed proteinaceous food. The suitability of this species for economic cultivation is discussed.     

Female Oviposition Decisions and Their Impact on Progeny Life-History Traits

An important factor affecting the life-history of an organism is parental investment in reproduction: reproductive decisions are almost invariably costly. Therefore, reproductive decisions should be beneficial in terms of increased offspring number or fitness. For example, egg laying decisions in many insects can influence resource availability of the offspring through changes in the larval density, and resource availability will have effects on many life-history traits. Here we studied whether female reproductive decisions affect offspring fitness in Callosobruchus maculatus seed beetles. Females laid more eggs on black-eye beans than on mung beans. However, when the difference in the surface area of the beans was accounted for, the number of eggs was not higher in black-eye beans. This together with the poisson distribution of eggs on each of the bean types suggests that females tend to lay their eggs randomly. We found that development time was longer, larval mortality lower and adult survival higher in black-eye beans. We also found interactions between bean type and larval density on size of the offspring such that in mung beans the emergence mass and pronotum width decreased with increasing larval density, but in black-eye beans larval density did not affect the size measures. We conclude that when there is a risk that larval denisty will become high within a bean and there is variable resources available, there exist clear benefits that females might obtain by choosing black-eye beans as a resource for their offspring. However, in contrast to many earlier studies, our results suggest that females may not be making any active oviposition decisions. Therefore, to unequivocally determine whether females do capitalise the potential benefits by active decision making, some further experimentation is required.     

Invasive mosquitoes, larval competition, and indirect effects on the vector competence of native mosquito species (Diptera: Culicidae)

Invasive arthropods that vector pathogens have the potential to influence pathogen transmission both directly, by becoming a novel pathogen vector, or indirectly, by interacting with native vectors. Adult mosquito size is influenced by food availability in the larval stage, and smaller, nutrient-deprived mosquitoes are, in some studies, more efficient viral vectors in the laboratory. This is the first study to examine the indirect impacts that larval competition between Aedes albopictus, an introduced mosquito species, and Ochlerotatus triseriatus, a native mosquito species and the primary vector for La Crosse virus (LACV) in the US, has on native mosquito larval survival, adult size, and vector competence. A. albopictus presence decreased Oc. triseriatus larval survival, but surviving Oc. triseriatus females were larger, potentially owing to a release from intraspecific competition. These larger, native females were more likely to develop both midgut and disseminated LACV infections than females emerging from monospecific treatments. Collectively, these results suggest a need to better understand the ecology of both native and invasive vector species, their interactions, and the potential for those interactions to alter vector-borne disease transmission.