Divergence of larval resource acquisition for water conservation and starvation resistance in Drosophila melanogaster

Laboratory selection experiments have evidenced storage of energy metabolites in adult flies of desiccation and starvation resistant strains of D. melanogaster but resource acquisition during larval stages has received lesser attention. For wild populations of D. melanogaster, it is not clear whether larvae acquire similar or different energy metabolites for desiccation and starvation resistance. We tested the hypothesis whether larval acquisition of energy metabolites is consistent with divergence of desiccation and starvation resistance in darker and lighter isofemale lines of D. melanogaster. Our results are interesting in several respects. First, we found contrasting patterns of larval resource acquisition, i.e., accumulation of higher carbohydrates during 3rd instar larval stage of darker flies versus higher levels of triglycerides in 1st and 2nd larval instars of lighter flies. Second, 3rd instar larvae of darker flies showed ~40?h longer duration of development at 21°C; and greater accumulation of carbohydrates (trehalose and glycogen) in fed larvae as compared with larvae non-fed after 150?h of egg laying. Third, darker isofemale lines have shown significant increase in total water content (18%); hemolymph (86%) and dehydration tolerance (11%) as compared to lighter isofemale lines. Loss of hemolymph water under desiccation stress until death was significantly higher in darker as compared to lighter isofemale lines but tissue water loss was similar. Fourth, for larvae of darker flies, about 65% energy content is contributed by carbohydrates for conferring greater desiccation resistance while the larvae of lighter flies acquire 2/3 energy from lipids for sustaining starvation resistance; and such energy differences persist in the newly eclosed flies. Thus, larval stages of wild-caught darker and lighter flies have evolved independent physiological processes for the accumulation of energy metabolites to cope with desiccation or starvation stress.     

Relationship between adult and larval host plant selection and larval performance in the generalist moth, Trichoplusia ni

Adult oviposition preferences are expected to correlate with host plant suitability for the development of their offspring. For most lepidopteran species, this is particularly important as the hatching neonate larvae of many species are relatively immobile. Thus, the site of oviposition chosen by a female adult can greatly influence the probability of survival for her offspring. In the present study, we investigated the oviposition preference of adult Trichoplusia ni moths for six plant species to determine whether they could accurately rank the suitability of the plants for larval development. We also compared oviposition preferences to neonate larval acceptance and preference to determine whether the adult host range matched that of larval diet breath. Our results indicate that in two-choice and no-choice tests adult T. ni were able to rank the plants accurately, with the exception of anise hyssop. However, when given a choice of all six plants together, they laid more eggs on a plant that was not suitable for larval survival. Larvae accepted and fed on all plants in no-choice tests, and accurately ranked them according to larval performance. We conclude that neonate larvae are better able than adults to rank plants according to larval performance, and that larval diet breadth is wider than the range of plants accepted by adults. We also provide a discussion of the reduced accuracy of adult oviposition preference with increased plant choices.     

Experimental Evidence for Nutrition Regulated Stress Resistance in Drosophila ananassae

Background

The amount and quality of nutrients consumed by organisms have a strong impact on stress resistance, life-history traits and reproduction. The balance between energy acquisition and expenditure is crucial to the survival and reproductive success of animals. The ability of organisms to adjust their development, physiology or behavior in response to environmental conditions, called phenotypic plasticity, is a defining property of life. One of the most familiar and important examples of phenotypic plasticity is the response of stress tolerance and reproduction to changes in developmental nutrition. Larval nutrition may affect a range of different life-history traits as well as responses to environmental stress in adult.

Principal Findings

Here we investigate the effect of larval nutrition on desiccation, starvation, chill-coma recovery, heat resistance as well as egg to adult viability, egg production and ovariole number in Drosophila ananassae. We raised larvae on either protein rich diet or carbohydrate rich diet. We found that flies consuming protein rich diet have higher desiccation and heat shock resistance whereas flies developed on carbohydrate rich diet have higher starvation and cold resistance. Egg production was higher in females developed on protein rich diet and we also found trade-off between egg production and Egg to adult viability of the flies. Viability was higher in carbohydrate rich diet. However, sex specific viability was found in different nutritional regimes. Higher Egg production might be due to higher ovariole number in females of protein rich diet.

Conclusion

Thus, Drosophila ananassae adapts different stress tolerance and life-history strategies according to the quality of the available diet, which are correlated with phenotypic adjustment at anatomical and physiological levels.     

Testing the plant stress hypothesis: stressed plants offer better food to an insect herbivore

Temperature and nutrition are among the most important environmental factors affecting ectotherm growth. As temperature and host‐plant quality often co‐vary in nature, the interaction between the two is of potentially high ecological importance for herbivorous insects. We here use the temperate‐zone butterfly Pieris napi L. (Lepidoptera: Pieridae) to investigate interactive effects of larval rearing temperature and host‐plant quality (by manipulating water availability) on larval growth. As growth rates have been hypothesized to govern stress tolerance, we additionally assessed adult starvation resistance. Butterflies followed the ‘temperature‐size rule’, which states that body size increases at lower developmental temperatures, proximately caused by differences in growth increment, which resulted from increased consumption at the lower temperature. Larvae benefitted from feeding on stressed plants from the low‐water regime by having higher body mass, growth rate, and food conversion efficiency, thus supporting the plant stress hypothesis, which predicts that plant quality for herbivores should increase if stress is imposed on plants. Some effects of host‐plant quality on larval growth parameters were as strong as or even stronger than effects of temperature, whereas interactive effects between temperature and food quality were scarce. At the low temperature, adult starvation resistance was higher than at the higher temperature and females were more resistant than males, whereas plant water regime had no clear impact. No evidence was found for a trade‐off between growth rate and starvation resistance. This study illustrates the importance of considering effects of host‐plant quality along with variation in other environmental factors for estimating the impact of environmental changes on herbivorous species.     

The impact of food type, temperature and starvation on larval development of Balanus amphitrite Darwin (Cirripedia: Thoracica)

The impact of diatom food species (Chaetoceros calcitrans and Skeletonema costatum), temperature and starvation on the larval development of Balanus amphitrite was evaluated. Starvation threshold levels for different ages of larvae (0- to 5-day-old) fed with C. calcitrans and S. costatum and then starved at 5, 15 and 25 °C temperature were estimated as ultimate recovery hour (URH; denoting the starvation point in hours at the end of which larvae can recover and continue development). Effect of temperature on starvation threshold varied significantly with larval age and food species. The URH declined with larval age at 5 °C, but not at 15 and 25 °C. The URH and grazing rates were high for early instars fed on C. calcitrans, and for advanced instars fed on S. costatum. Carbon gain through feeding was maximum for 2-day-old larvae when fed with C. calcitrans and decreased with larval age. However, when fed with S. costatum carbon gain increased with larval age. This confirms that with development the utility of food types changes. The differences in the carbon gain can be attributed to differences in grazing rate due to variations in the size of the diatom cells, larval intersetular distance, diatom sinking rate and the photo-taxic behavior of larvae. Molting was observed at times when larvae were undergoing starvation and this could be viewed as stress-induced molting, and it differed with the larval age and food organisms.     

Family matters: effect of host plant variation in chemical and mechanical defenses on a sequestering specialist herbivore

Insect herbivores contend with various plant traits that are presumed to function as feeding deterrents. Paradoxically, some specialist insect herbivores might benefit from some of these plant traits, for example by sequestering plant chemical defenses that herbivores then use as their own defense against natural enemies. Larvae of the butterfly species Battus philenor (L.) (Papilionidae) sequester toxic alkaloids (aristolochic acids) from their Aristolochia host plants, rendering larvae and adults unpalatable to a broad range of predators. We studied the importance of two putative defensive traits in Aristolochia erecta: leaf toughness and aristolochic acid content, and we examined the effect of intra- and interplant chemical variation on the chemical phenotype of B. philenor larvae. It has been proposed that genetic variation for sequestration ability is ??invisible to natural selection?? because intra- and interindividual variation in host-plant chemistry will largely eliminate a role for herbivore genetic variation in determining an herbivore??s chemical phenotype. We found substantial intra- and interplant variation in leaf toughness and in the aristolochic acid chemistry in A. erecta. Based on field observations and laboratory experiments, we showed that first-instar larvae preferentially fed on less tough, younger leaves and avoided tougher, older leaves, and we found no evidence that aristolochic acid content influenced first-instar larval foraging. We found that the majority of variation in the amount of aristolochic acid sequestered by larvae was explained by larval family, not by host-plant aristolochic acid content. Heritable variation for sequestration is the predominant determinant of larval, and likely adult, chemical phenotype. This study shows that for these highly specialized herbivores that sequester chemical defenses, traits that offer mechanical resistance, such as leaf toughness, might be more important determinants of early-instar larval foraging behavior and development compared to plant chemical defenses.     

IMMUNE RESPONSE TO PARASITISM REDUCES RESISTANCE OF DROSOPHILA MELANOGASTER TO DESICCATION AND STARVATION

Abstract In natural populations, organisms experience simultaneously biotic (e.g., competitors and parasites) and abiotic (e.g., temperature and humidity) stresses. Thus, species must have the capacity to respond to combinations of stressors. How does interaction between biotic and abiotic stress affect organismal performance? To address this question, I studied stress resistance of adult Drosophila melanogaster that survived parasitic attack (as larvae) by the parasitoid Asobara tabida. To determine the impact of genotype on stress resistance, I measured survival under desiccation and starvation of flies within isofemale (genetic) lines. Survivors of parasitism had slightly reduced survivorship compared to unparasitized relatives when both were unstressed, and this difference was exacerbated by desiccation and starvation. These results indicate multiple stressors can compound each other's individual negative effects on fitness. Moreover, isofemale lines differed in their sensitivity to environmental stress and to parasitism. Consequently, genotypic differences in sensitivity to stress may reflect differences in investment priorities between traits that promote survival over other life‐history characters.     

Adult beetles compensate for poor larval food conditions

Life history traits of herbivores are highly influenced by the quality of their hosts, i.e., the composition of primary and secondary plant metabolites. In holometabolous insects, larvae and adults may face different host plants, which differ in quality. It has been hypothesised that adult fitness is either highest when larval and adult environmental conditions match (environmental matching) or it may be mainly determined by optimal larval conditions (silver spoon effect). Alternatively, the adult stage may be most decisive for the actual fitness, independent of larval food exposure, due to adult compensation ability. To determine the influence of constant versus changing larval and adult host plant experiences on growth performance, fitness and feeding preferences, we carried out a match–mismatch experiment using the mustard leaf beetle, Phaedon cochleariae. Larvae and adults were either constantly reared on watercress (natural host) or cabbage (crop plant) or were switched after metamorphosis to the other host. Growth, reproductive traits and feeding preferences were determined repeatedly over lifetime and host plant quality traits analysed. Differences in the host quality led to differences in the development time and female reproduction. Egg numbers were significantly influenced by the host plant species experienced by the adults. Thus, adults were able to compensate for poor larval conditions. Likewise, the current host experience was most decisive for feeding preferences; in adult beetles a feeding preference was shaped regardless of the larval host plant. Larvae or adults reared on the more nutritious host, cabbage, showed a higher preference for this host. Hence, beetles most likely develop a preference when gaining a direct positive feedback in terms of an improved performance, whereby the current experience matters the most. Highly nutritious crop plants may be, in consequence, all the more exploited by potential pests that may show a high plasticity in reproduction and feeding preferences.     

Resistance to environmental stress in Drosophila ananassae: latitudinal variation and adaptation among populations

Geographical variation in traits related to fitness is often the result of adaptive evolution. Stress resistance traits in Drosophila often show clinal variation, suggesting that selection affects resistance traits either directly or indirectly. Multiple stress resistance traits were investigated in 45 natural populations of Drosophila ananassae collected from all over India. There was significant positive correlation between starvation resistance and lipid content. Significant negative correlations between desiccation and lipid content and between desiccation and heat resistance were also found. Flies from lower latitudes had higher starvation resistance, heat resistance and lipid content but the pattern was reversed for desiccation resistance. These results suggest that flies from different localities varied in their susceptibility to starvation because of difference in their propensity to store body lipid. Multiple regression analysis provided evidence of climatic selection driven by latitudinal variation in the seasonal amplitude of temperature and humidity changes within the Indian. Finally, our results suggest a high degree of variation in stress resistance at the population level in D. ananassae.     

Contrasting egg and larval performances help explain polyphagy in a florivorous butterfly

We examined both egg and larval performances in the polyphagous butterfly Parrhasius polibetes (Lycaenidae) using two host plants differing in morphological and ecological traits. Oviposition on mixed and pure patches of Schefflera vinosa (Araliaceae) and Pyrostegia venusta (Bignoniaceae), as well as the fate of eggs laid on both hosts, was assessed. To disentangle the effects of egg origin and host quality on larval performance, eggs were collected from Schefflera and Pyrostegia, and the corresponding newly hatched larvae were reared either on the natal (control) or non-natal (experimental) host. Lastly, we evaluated whether early and late instars are able to switch to alternative hosts. In both mixed and pure patches, parasitism was significantly lower, and oviposition and hatching rates were significantly higher for eggs laid on Schefflera than on Pyrostegia. Survivorship did not differ among treatments. Larvae fed with Pyrostegia were heavier than those fed with Schefflera, regardless of egg origin. Only early instars fed with Schefflera switched to Pyrostegia in the tests; in the remaining cases, larvae fed on the alternative hosts significantly less than on the controls. Our results help to explain why the use of multiple hosts by P. polibetes is maintained in nature, as the host conferring superior egg survival may incur poor larval performance and vice versa. Oviposition pattern is better understood from a tri-trophic rather than a bi-trophic perspective. Our study also highlights the monophagous condition of individual P. polibetes larvae; the constraint for switching to novel hosts is dependent on both larval instar and host plant species.     

The effects of adaptation to urea on feeding rates and growth in Drosophila larvae

A collection of forty populations were used to study the phenotypic adaptation of Drosophila melanogaster larvae to urea‐laced food. A long‐term goal of this research is to map genes responsible for these phenotypes. This mapping requires large numbers of populations. Thus, we studied fifteen populations subjected to direct selection for urea tolerance and five controls. In addition, we studied another twenty populations which had not been exposed to urea but were subjected to stress or demographic selection. In this study, we describe the differentiation in these population for six phenotypes: (1) larval feeding rates, (2) larval viability in urea‐laced food, (3) larval development time in urea‐laced food, (4) adult starvation times, (5) adult desiccation times, and (6) larval growth rates. No significant differences were observed for desiccation resistance. The demographically/stress‐selected populations had longer times to starvation than urea‐selected populations. The urea‐adapted populations showed elevated survival and reduced development time in urea‐laced food relative to the control and nonadapted populations. The urea‐adapted populations also showed reduced larval feeding rates relative to controls. We show that there is a strong linear relationship between feeding rates and growth rates at the same larval ages feeding rates were measured. This suggests that feeding rates are correlated with food intake and growth. This relationship between larval feeding rates, food consumption, and efficiency has been postulated to involve important trade‐offs that govern larval evolution in stressful environments. Our results support the idea that energy allocation is a central organizing theme in adaptive evolution.     

Biogeography and phenology of oviposition preference and larval performance of <Emphasis Type="Italic">Pieris virginiensis</Emphasis> butterflies on native and invasive host plants

In invaded environments, formerly reliable cues might no longer be associated with adaptive outcomes and organisms can become trapped by their evolved responses. The invasion of Alliaria petiolata (garlic mustard) into the native habitat of Pieris virginiensis (West Virginia White) is one such example. Female butterflies oviposit on the invasive plant because it is related to their preferred native host plant Cardamine diphylla (toothwort), but larvae are unable to complete development. We have studied the impact of the A. petiolata invasion on P. virginiensis butterflies in the Southeastern USA by comparing oviposition preference and larval survival on both plants in North Carolina (NC) populations without A. petiolata and West Virginia (WV) populations where A. petiolata is present. Larval survival to the 3rd instar was equally low in both populations when raised on A. petiolata. Mean oviposition preference on the two plants also did not differ between populations. However, we found a seasonal effect on preference between early and late season flights within WV populations. Late season females laid 99% of total eggs on A. petiolata while early season females utilized both host plants. Late season females were also less likely to lay eggs than early season females. This change in preference toward A. petiolata could be driven by the early senescence of C. diphylla and suggests a seasonal component to the impact of A. petiolata. Therefore, the already short flight season of P. virginiensis could become further constrained in invaded populations.     

Temperature and photoperiod affect stress resistance traits in Drosophila melanogaster

The long‐term survival of species and populations depends on their ability to adjust phenotypic values to environmental conditions. In particular, the capability of dealing with environmental stress to buffer detrimental effects on fitness is considered to be of pivotal importance. Resistance traits are readily modulated by a wide range of environmental factors. In the present study, Drosophila melanogaster Meigen is used to investigate plastic responses to temperature and photoperiod in stress resistance traits. The results reveal that stress resistance traits (cold, heat, starvation and desiccation resistance) are affected by the factors temperature and sex predominantly. Cooler temperatures compared with warmer temperatures increase cold tolerance, desiccation and starvation resistance, whereas they reduce heat tolerance. Except for heat resistance, females are more stress‐resistant than males. Stress resistance traits are also affected by photoperiod. Shorter photoperiods decrease cold tolerance, whereas longer photoperiods enhance desiccation resistance. Overall, thermal effects are pervasive throughout all measured resistance traits, whereas photoperiodic effects are of limited importance in the directly developing (i.e. nondiapausing) flies used here, suggesting that pronounced photoperiodic effects on stress resistance traits may be largely limited to, and triggered by, diapause‐inducing effects.     

Greater impact of host plant species on oviposition of a willow leaf beetle <Emphasis Type="Italic">Plagiodera versicolora</Emphasis> Laicharting (Coleoptera: Chrysomelidae) during the adult stage than in developing larval stage

In some herbivorous insects, such as Coleoptera and aphids, not only the host species of larvae, but also those of adults should be considered as key determinants of potential fecundity because oviposition is affected by the quality of host species during both larval and adult stages. This study examined the relatively greater impact on host species of the larval or adult stage on oviposition of the willow leaf beetle Plagiodera versicolora Laicharting (Coleoptera: Chrysomelidae). We conducted an experiment using a 2 × 2 experimental design, in which either of two different host plant species was fed in larval and adult stages. Females fed on a locally unavailable host Salix eriocarpa in the adult stage did not lay any eggs, but those fed on the locally available host S. babylonica laid 67–75 eggs on average, irrespective of larval host species. Such reproductively inactive females fed S. eriocarpa as an adult host recovered reproductive activity within 3 weeks after changing the host species to S. babylonica. This result indicated that the host species fed in the adult stage had a greater impact on oviposition than in the larval stage.     

Protein and carbohydrate composition of larval food affects tolerance to thermal stress and desiccation in adult Drosophila melanogaster

Larval nutrition may affect a range of different life history traits as well as responses to environmental stress in adult insects. Here we test whether raising larvae of fruit flies, Drosophila melanogaster, on two different nutritional regimes affects resistance to cold, heat and desiccation as well as egg production and egg-to-adult viability. We raised larvae on a carbohydrate-enriched and a protein-enriched growth medium. We found that flies developed on the high protein medium had increased heat and desiccation tolerance compared to flies developed on the carbohydrate-enriched medium. In contrast, flies developed on the carbohydrate-enriched growth medium recovered faster from chill coma stress compared to flies developed on a protein-enriched medium. We also found gender differences in stress tolerance, with female flies being more tolerant to chill coma, heat knockdown and desiccation stress compared to males. Egg production was highest in females that had developed on the protein-enriched medium. However, there was a sex-specific effect of nutrition on egg-to-adult viability, with higher viability for males developing on the sucrose-enriched medium, while female survival was highest when developing on the protein-enriched medium. Our study indicates that larval nutrition has a strong impact on the ability to cope with stress, and that the optimal nutrient composition varies with the type of stress.     

Influence of Dietary Experience on the Induction of Preference of Adult Moths and Larvae for a New Olfactory Cue

In Lepidoptera, host plant selection is first conditioned by oviposition site preference of adult females followed by feeding site preference of larvae. Dietary experience to plant volatile cues can induce larval and adult host plant preference. We investigated how the parent’s and self-experience induce host preference in adult females and larvae of three lepidopteran stem borer species with different host plant ranges, namely the polyphagous Sesamia nonagrioides, the oligophagous Busseola fusca and the monophagous Busseola nairobica, and whether this induction can be linked to a neurophysiological phenotypic plasticity. The three species were conditioned to artificial diet enriched with vanillin from the neonate larvae to the adult stage during two generations. Thereafter, two-choice tests on both larvae and adults using a Y-tube olfactometer and electrophysiological (electroantennography [EAG] recordings) experiments on adults were carried out. In the polyphagous species, the induction of preference for a new olfactory cue (vanillin) by females and 3^rd instar larvae was determined by parents’ and self-experiences, without any modification of the sensitivity of the females antennae. No preference induction was found in the oligophagous and monophagous species. Our results suggest that lepidopteran stem borers may acquire preferences for new olfactory cues from the larval to the adult stage as described by Hopkins’ host selection principle (HHSP), neo-Hopkins’ principle, and the concept of ‘chemical legacy.’     

Plant-mediated indirect effects of climate change on an insect herbivore

Anthropogenic climate change is a substantial challenge to biodiversity conservation, exerting direct effects on plants and animals alike. Herbivores may be additionally affected by indirect effects, mediated through, for instance, climate change-induced alterations in host-plant quality. Thus, climate change may pronouncedly impact long-evolved plant-animal interactions, but our knowledge is still in its infancy, particularly with regard to the combined effects of temperature and water availability. We here investigate the effects of simulated climate change, considering variation in both temperature and water availability, on (1) host-plant chemistry, (2) herbivore oviposition and larval feeding preference, and (3) larval and adult performance. As study system, we used the butterfly Pieris napi (Lepidoptera: Pieridae) and its host plant Sinapis alba (Brassicacae). Host-plant chemistry was affected by simulated climate change, with higher temperatures increasing the carbon-nitrogen ratio and concentrations of glucosinolates, while drought stress led to reduced glucosinolate concentrations. Both egg-laying females and larvae preferred plants with the highest concentrations of the glucosinolate glucosinalbin, potentially acting as oviposition and feeding stimulus. Herbivore performance was positively affected by plants grown at control temperatures or under drought stress and thus reduced glucosinolate concentrations. Hence, P. napi was not able to select the most profitable host. Our study indicates that (1) climate-induced changes in plant chemistry may exert indirect effects on herbivores, (2) effects of climate change will depend on the magnitude of change in specific abiotic parameters and their interactions, whereby positive (e.g. drought) and negative (e.g. temperature) effects may even cancel out each other, and (3) changes in critical chemical cues may diminish host-plant detectability and thereby result in reduced realised fecundity. We thus highlight the important role of temperature and water availability on plant chemistry, which may change interactions between insects and plants.     

Interactions between desiccation resistance,host-plant contact and the thermal biology of a leaf-dwelling sub-antarctic caterpillar,Embryonopsis halticella (Lepidoptera: Yponomeutidae)

During May 1997 thermal tolerance, supercooling point (SCP), low and high temperature survival, and desiccation resistance were examined in field-fresh Embryonopsis halticella Eaton larvae from Marion Island. SCPs were also examined in acclimated larvae, larvae starved for seven days, larvae within their leaf mines, and in larvae exposed to ice crystals. Field-fresh larvae had a critical minimum temperature (CT(Min)) and critical maximum temperature (CT(Max)) of 0 degrees C and 39.7 degrees C, respectively. Mean SCP of field-fresh caterpillars was -20.5 degrees C and this did not change with starvation. Field-fresh larvae did not survive freezing and their lower lethal temperatures (70% mortality below -21 degrees C) and survival of exposure to constant low temperatures (100% mortality after 12hrs at -19 degrees C) indicated that they are moderately chill tolerant. SCP frequency distributions were unimodal for field-fresh larvae, but became bimodal at higher acclimation temperatures. Contact with ice-crystals caused an increase in SCP (-6.5 degrees C), but contact with the host plant had less of an effect at higher subzero temperatures. It appears that the remarkable desiccation resistance of the larvae is selected for by the absence of a boundary layer surrounding their host plant, caused by constant high winds. This suggests that the low SCPs of E. halticella larvae may have evolved as a consequence of pronounced desiccation resistance.     

Life history and host range of Sauris nr. purpurotincta,an unsuitable biological control agent for Chinese tallowtree

Foreign surveys in China discovered a defoliating insect species feeding on the leaves of Chinese tallowtree (Triadica sebifera), an invasive weed of the southeastern U.S.A. The life history of this species, Sauris nr. purpurotincta (Lepidoptera: Geometridae), was examined and larval no-choice and adult multiple-choice host range tests were conducted in quarantine to evaluate their suitability for biological control of Chinese tallowtree. The results indicated that the larvae have five instars and require approximately 22 days to complete development to the adult stage. Host range tests indicated that the larvae could not feed and complete development on most species tested. However, 40% of the larvae survived when fed leaves of Hippomane mancinella, a state-listed endangered species in Florida, and all larvae survived when fed Morella cerifera, a common native species of the southeastern U.S.A. Multiple-choice oviposition tests indicated eggs were laid on leaves of both a south Florida native plant Gymnanthes lucida and Chinese tallowtree. Considering this broad host range, this species will not be considered further for biological control of Chinese tallowtree in the U.S.A.     

Effect of food plant switching by a herbivore on its parasitoid: Cotesia melanoscela development in Lymantria dispar exposed to reciprocal dietary crosses

1. Host plant switching by dispersing early instar lepidopterans could have implications for parasitoid performance, but this possibility has not been evaluated thoroughly. 2. The relative growth rates of Lymantria dispar parasitized by Cotesia melanoscela, and the weight of larvae at the time of parasitoid emergence, were affected most by the second larval food plant consumed. 3. The relative growth rates, pupal weights, weight of larva at the time of parasitoid emergence, and development times of L. dispar were affected significantly by the second larval food plant consumed. 4. Development time and size of Cotesia melanoscela were affected most by the second larval food plant consumed. 5. Parasitoid performance was affected most by the larval host’s relative growth rate and the final weight of the host larva at the time of parasitoid emergence. 6. Host plant switching affected the weight of L. dispar larvae at the time of parasitoid emergence, but the effect of switching per se was not a significant factor in C. melanoscela size or development. 7. Lymantria dispar larvae that fed on Populus as their second host outperformed larvae that fed ultimately on Acer. 8. Parasitoids yielded from L. dispar larvae that fed ultimately on Populus outperformed parasitoids yielded from larvae that fed ultimately on Acer. 9. Per cent mortality of L. dispar due to parasitism and percentage adult C. melanoscela emergence were highest in parasitized larvae fed Populus, poor in hosts fed Acer, and intermediate in switching larvae.