Presence of predatory wasps and stinkbugs alters foraging behavior of cryptic and non-cryptic caterpillars on plantain (Plantago lanceolata)

We examined the foraging patterns of two species of caterpillar (Junonia coenia: Nymphalidae and Spilosoma congrua: Arctiidae) that contrast in feeding specialization and crypticity on plantain (Plantago lanceolata) in the absence and presence of two different insect predators [stinkbugs, Podisus maculiventris (Pentatomidae) and wasps, Polistes fuscatus (Vespidae)]. Junonia larvae were quite apparent to human observers, feeding on upper leaf surfaces during daylight, whereas Spilosoma larvae were relatively cryptic, often hiding under leaves and in soil crevices during daylight. In the presence of either predator species, the non-cryptic Junonia caterpillars more quickly left the plant on which they were initially placed and were less apparent than Junonia larvae not exposed to predators. The presence of predators had no detectable influence on where the caterpillars occurred on the plants (new, intermediate-aged or mature leaves, or reproductive stalks). Surprisingly, the predators influenced the behavior of the inherently cryptic Spilosoma: the apparency of these larvae at night increased when wasps had access to the plots during the day. Survivorship of the non-cryptic Junonia was less than 12% when stinkbugs were present compared to 60% in their absence. Although the presence of wasps resulted in a lower relative growth rate for the non-cryptic Junonia larvae, the indirect effect of predators on reduction in survivorship due to alterations in prey growth rate through behavioral changes was less than 3%. After taking into account the decline in caterpillars per plot through predation, we found that both the amount of leaves eaten and the proportion of plants eaten were altered on plots with predators present, which suggests that the caterpillars' increased consumption countered increased maintenance costs due to the presence of predators. Overall, our results indicate that hostplant size, level of predation and type of predator can influence the degree to which these caterpillars react to the presence of insect predators. In contrast, degree of inherent feeding specialization and cryptic behavior seemed to have little effect on the expression of reactive behaviors of these caterpillars to predators.     

Effects of plant spinescence on large mammalian herbivores

Summary Plant thorns and spines had these effects on the feeding behaviour of the three species of browsing ungulate that we studied, kudu, impala and domestic goats: (i) bite sizes were restricted, in most cases to single leaves or leaf clusters; (ii) hooked thorns retarded biting rates; (iii) the acceptability of those plant species offering small leaf size in conjunction with prickles was lower, at least for the kudus, than those of other palatable plant species; (iv) the inhibitory effect of prickles on feeding was much less for the smaller impalas and goats than for the larger kudus; (v) from certain hook-thorned species the kudus bit off shoot ends despite their prickles; (vi) for certain straight-thorned species the kudus compensated partially for the slow eating rates obtained by extending their feeding durations per encounter. Most spinescent species were similar in their acceptability to the ungulates to unarmed palatable species, despite higher crude protein contents in their foliage than the latter. Such structural features furthermore reduce the tissue losses incurred by plants per encounter by a large ungulate herbivore, by restricting the eating rates that the animals obtain. In this way prickles function to restrict foliage losses to large herbivores below the levels that might otherwise occur.     

Generalist caterpillar prey are more palatable than specialists for the generalist predator Iridomyrmex humilis

Summary Experiments are described which test the hypothesis that more host-specific species of caterpillars should be less aceptable to a generalist predator than polyphagous species. Caterpillars of all species were tested in paired choice tests with the Argentine ant, Iridomyrmex humilis. Experiments were replicated ten times, videotaped and later analyzed. Brightly colored specialist species (normally considered to be aposematic) were clearly the least palatable, while more cryptic specialists were also significantly less acceptable than generalists overall. Leaf-tying species were considered separately; all were highly palatable independent of host range. The results indicate that among caterpillars that do not construct leaf shelters, those with a wide post range are more acceptable than those with a narrow host range. This is consistent with the notion that generalist predators provide selection pressure favoring narrow host range in their herbivorous prey.     

Avoidance of unpalatable prey by predaceous diving beetle larvae: The role of hunger level and experience (Coleoptera: Dytiscidae)

The effects of hunger and experience on the avoidance of unpalatable prey were examined. Larvae of the predaceous diving beetle,Dytiscus verticalis, after feeding on one of two feeding regimes, were offered palatable and unpalatable prey during a series of trials. Consumption of palatable prey (calf heart) was not affected by hunger or experience. Avoidance of unpalatable prey (tails of the red-spotted newtNotophthalmus viridescens) decreased with increased hunger, with hungrier predators sampling unpalatable prey more often. Although the overall level of avoidance varied across trials, the degree of difference in avoidance between predators at different hunger levels remained relatively constant across trials. Beetle larvae responded to an increase in their feeding regime within 36 h (after two trials), by becoming more selective. In a separate experiment, hunger level affected the number of beetle larvae that seized unpalatable newt tails, but experience did not.     

Larval feeding experience influences adult predator acceptance of chemically defended prey

Generalist predatory paper wasps, Polistes dominulus, experience plant secondary defensive compounds as developing larvae through their herbivorous lepidopteran caterpillar prey and as adults through attacking caterpillars while foraging. We evaluated the role that larval and early adult experience with unpalatable prey plays in subsequent foraging choices by adult wasps. For periods of two or four weeks, caged wasps were raised exclusively on caterpillars of either unpalatable Buckeye, Junonia coenia, that sequester substantial levels of iridoid glycosides (IG) or on Painted Lady, Vanessa cardui, that contain very low levels of IG. Wasps were then allowed to forage on both caterpillar species simultaneously. Patterns of prey capture differed significantly based on previous prey experience. Regardless of previous feeding experience, adult wasps overwhelmingly preferred to take Vanessa. Yet Junonia-experienced wasps continued to attack and take back to the nest over 50% more Junonia than did Vanessa-experienced wasps. The longer the wasps' larval experience with Junonia, the more likely they were to capture Junonia caterpillars. However, the life stage at which the wasps experienced Junonia was also influential as young adult experience with the unpalatable prey was more of a deterrent than was experience strictly as larvae for Junonia-experienced wasps. The results demonstrate that, in these predators, previous experience with deterrent chemicals during their larval development alters patterns of prey acceptability to the adult insects.     

Larval mortality and population regulation in the butterfly Danaus chrysippus in Ghana

An ecological study was made of a population of caterpillars of the African queen butterfly (Danaus chrysippus) feeding on three species of asclepiad plants at Nungua, Ghana, over a nine month period in 1972-73. The principal sources of mortality of caterpillars are probably the parasitic hymenopterans Apanteles chrysippi and Charops sp. There is an inverse correlation between the population of caterpillars and incidence of parasitization. This, and other evidence, suggests that the two parasites are important in limiting the population of Danaus chrysippus below the level imposed by the available food supply. Early instar caterpillars are probably palatable to birds but later instars may be edible or emetic depending on the toxicity of their food plant. It is suggested that the early instar caterpillars are cryptic whilst late instars are cryptic from a distance but conspicuous from nearby, and these may be aposematic or mimetic according to the nature of the food plant. Caterpillars parasitized by Apanteles are paler and hence more cryptic than normal caterpillars. There is also a green, cryptic morph present in the population at low frequency. It is suggested that there is a correlation between colour of caterpillars and the principal source of mortality: i.e., cryptic caterpillars are palatable to birds, suffer heavy predation but a low incidence of parasitization, whilst conspicuous caterpillars are unpalatable to many birds, suffer little predation but have a high incidence of parasitization.     

Behavioral mechanisms underlie an ant-plant mutualism

Predators can reduce herbivory by consuming herbivores (a consumptive effect) and by altering herbivore behavior, life history, physiology or distribution (non-consumptive effects). The non-consumptive, or trait-mediated, effects of predators on prey may have important functions in the dynamics of communities. In a facultative ant-plant mutualism, we investigated whether these non-consumptive effects influenced the host plants of prey. Here, predaceous ants (Forelius pruinosus) consume and disturb a dominant lepidopteran folivore (Bucculatrix thurberiella) of wild cotton plants (Gossypium thurberi). Season-long ant exclusion experiments revealed that ants had a larger proportional effect on damage by B. thurberiella than on caterpillar abundance, a result that suggests ants have a strong non-consumptive effect. Behavioral experiments conducted in two populations over 2 years demonstrated that B. thurberiella caterpillars were substantially less likely to damage wild cotton leaves in the presence of ants due to ant-induced changes in caterpillar behavior. In the absence of ants caterpillars spent more time stationary (potential feeding time) and less time dropping from leaves by a thread of silk than when ants were present. Furthermore, ants altered the spatial distribution of both caterpillars and damage; caterpillars spent relatively more time on the upper surfaces of leaves and caused damage further from the leaf margin in ant exclusion treatments. Both direct encounters with ants and information conveyed when ants walked onto leaves were key events leading to the anti-predator behaviors of caterpillars. This study contributes to a small body of evidence from terrestrial systems demonstrating that the trait-mediated effects of predators can cascade to the host plants of prey.     

Effects of prey quantity and quality on predatory wasps

1. The simultaneous effects of prey quantity and prey quality on fitness correlates of the predatory wasp Polistes fuscatus were examined in a glasshouse study. Prey quantity was manipulated by providing prey in excess (high quantity) or one‐third of that (low quantity). Prey quality was manipulated by providing either palatable (Manduca sexta) caterpillars or unpalatable (Junonia coenia) caterpillars. 2. The effect of prey quality on wasp production depended on prey quantity. Nests given unpalatable prey produced few wasps whereas nests given palatable prey increased wasp production with increased prey. 3. The low production of nests given unpalatable prey reflected the low acceptability of those prey. The wasps preferred the palatable prey and learned to reject the unpalatable prey. With no choice of prey, they took only enough unpalatable prey to develop a small nest or colony. 4. A diet of unpalatable prey also resulted in smaller wasps and reduced the proportion of males produced, from about 40% to just 8–14%, depending on the year.     

Aversive reactions of two invertebrate predators to European red–black insects

Prey species gain protection by imitating signals of unpalatable models in defensive mimicry. Mimics have been traditionally classified as Batesian (palatable mimic resembling an unpalatable model) or Müllerian (unpalatable mimic resembling a similarly unpalatable model). However, recent studies suggest that rather than discrete categories, the phenomenon of mimicry can be better understood as a continuum. The level of unpalatability of defended prey is a key factor in determining the type of mimetic relationship. Herein, we used insects (ladybugs and true bugs) from a putative European “red–black” mimetic complex as experimental models of defended species and crickets as a control prey. We offered the prey to two species of sympatric invertebrate predators (praying mantis and spider) and video recorded the interactions. We tested three alternative hypotheses, namely (i) the three red–black species tested are similarly defended against both predators; (ii) some red–black species are better defended than others against both predator species, and (iii) the effectiveness of the red–black species defenses is predator dependent. Both predators attacked all prey types with a similar frequency. But while all three red–black species similarly elicited aversive behaviors in spiders, the mantises' aversive reactions varied depending on the prey species. Our results provide support to the third hypothesis, suggesting that the same prey species can fall into different parts of the spectrum of palatability–unpalatability depending on the type of predator.     

Aversive Learning in the Praying Mantis (<Emphasis Type="Italic">Tenodera aridifolia</Emphasis>), a Sit and Wait Predator

Animals learn to associate sensory cues with the palatability of food in order to avoid bitterness in food (a common sign of toxicity). Associations are important for active foraging predators to avoid unpalatable prey and to invest energy in searching for palatable prey only. However, it has been suggested that sit-and-wait predators might rely on the opportunity that palatable prey approach them by chance: the most efficient strategy could be to catch every available prey and then decide whether to ingest them or not. In the present study, we investigated avoidance learning in a sit-and-wait predator, the praying mantis (Tenodera aridifolia). To examine the effects of conspicuousness and novelty of prey on avoidance learning, we used three different prey species: mealworms (novel prey), honeybees (novel prey with conspicuous signals) and crickets (familiar prey). We sequentially presented the prey species in pairs and made one of them artificially bitter. In the absence of bitterness, the mantises consumed bees and crickets more frequently than mealworms. When the prey were made bitter, the mantises still continued to attack bitter crickets as expected. However, they reduced their attacks on bitter mealworms more than on bitter bees. This contrasts with the fact that conspicuous signals (e.g. coloration in bees) facilitate avoidance learning in active foraging predators. Surprisingly, we found that the bitter bees were totally rejected after an attack whereas bitter mealworms were partially eaten (~35%). Our results highlight the fact that the mantises might maintain a selection pressure on bees, and perhaps on aposematic species in general.     

Foliage acceptability to browsing ruminants in relation to seasonal changes in the leaf chemistry of woody plants in a South African savanna

Summary We investigated seasonal changes in food selection by hand-reared kudus and impalas in savanna vegetation in northern Transvaal, South Africa. The acceptability of the leaves of woody plants to these animals was compared with leaf concentrations of nutrients, fibre components and old leaf phenophases. No consistently significant correlation was found between acceptability and any single chemical factor. Based on an a priori palatability classification, discriminant function analysis separated relatively palatable species from unpalatable species in terms of a linear combination of protein and condensed tannin concentrations. The high acceptability of certain otherwise unpalatable species during the new leaf phenophase was related to elevation of protein levels relative to condensed tannin contents. Species were added to the diet during the dry season approximately in the order of their relative protein-condensed tannin difference.     

Daily foraging schedule of field colonies of the eastern tent caterpillar Malacosoma americanum

Summary The daily foraging patterns of seven colonies of the eastern tent caterpillar, Malacosoma americanum, were monitored photoelectronically during the last three larval stadia to provide the first detailed record of the foraging behavior of a gregarious caterpillar under field conditions. Colonies were active an average of 49.3% of each day. Three bouts of foraging, centered about 0600 h, 1500 h and 2000 h (EST), occurred daily during the fourth and fifth stadia. Although ambient temperatures were less favorable for foraging and food processing than at other times of the day, the caterpillars were most active at dusk and dawn, and spent comparatively little time away from the tent during the daylight hours. In the last (sixth) stadium, the caterpillars foraged only under the cover of darkness. A lack of relationship between the rate at which the caterpillars processed food and the spacing of their feeding bouts, indicates that this species follows a schedule of feeding and growth shaped by factors other than those directly related to feeding efficiency and ambient temperature. Colony foraging patterns may reduce caterpillar mortality by minimizing contact between larvae and day-active predators and parasitiods.     

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.     

Leaf ties as colonization sites for forest arthropods: an experimental study

Abstract.  1. Secondary colonization of leaf shelters constructed by caterpillars has been reported from a number of systems. Both the mechanism (larval or adult movement vs. oviposition) and the cues used by arthropods in locating leaf shelters, however, have received little attention.
2. Artificial leaf shelters (i.e. leaf ties or pairs of leaves clipped together to form sandwiches) were constructed on understorey white oak ( Quercus alba L.) trees and the abundance and species composition of arthropods colonizing and ovipositing on leaf pairs was examined in three treatments: occupied leaf ties (containing a leaf-tying caterpillar), unoccupied leaf ties, and non-tied control leaves.
3. The density of arthropods present in the occupied and unoccupied leaf ties after two weeks was seven and four times greater respectively, than non-tied controls. The guild composition of these early colonists differed among treatments, with the highest densities of leaf chewers, scavengers, and predators in occupied ties and the lowest densities in non-tied controls.
4. The densities of all arthropods ovipositing on leaf pairs in the occupied and unoccupied leaf tie treatments were four and three times greater than non-tied controls. Leaf-chewing insects (including leaf-tiers and non-tying inquiline species) and scavengers showed strong oviposition preferences for tied leaves. However, most species of leaf-tying caterpillars and the psocids (Psocoptera) did not distinguish between occupied and unoccupied ties, suggesting that these groups do not use occupancy-related cues in selecting oviposition sites.     

Cascading effects of predatory fish on the composition of benthic algae in high‐altitude streams

Cascading effects of predators can affect ecosystem properties by changing plant biomass, distribution and assemblage composition. Using data from field surveys and whole‐stream experiments we tested the hypothesis that predatory trout change assemblage composition of benthic algae in high‐elevation streams mediated by grazer behavior. Field surveys revealed that the taxonomic composition of algal assemblages differed significantly between streams that contained trout and those that were fishless; but comparisons of palatable versus unpalatable algal taxa between fish and fishless streams were equivocal because of high natural variability. Therefore, we tested for a behavioral (non‐consumptive) trophic cascade experimentally by adding brook trout chemical cues to six naturally fishless streams for 25 days and compared responses of grazers and algae to six reference streams without fish cues added. Algal response variables included rates of change in the abundance of three physiognomic categories, from most palatable (attached erect and prostrate diatoms) to least palatable (non‐diatoms), as determined from food selectivity analyses of the most common grazers (mayflies and caddisflies). Fish cues did not affect the mean densities or changes in densities of total grazers or any individual grazer species. However, in streams where fish cues were added, rates of accrual of attached erect diatoms, which was the preferred algal type for the grazer most vulnerable to trout predation (Baetis), were higher and their densities increased significantly faster with increasing densities of this grazer species than in reference streams. Results of his experiment support the hypothesis that predator induced suppression of grazer foraging behavior, rather than cascading effects of top predators on grazer density, may contribute to variation in the composition of algal assemblages among streams by allowing proliferation of most palatable algal species.     

Effects of chlorogenic acid-and tomatine-fed caterpillars on the behavior of an insect predator

If generalist insect predators are a selective force contributing to patterns of feeding specialization by insect herbivores, then predators should be deterred from eating allelochemical-fed prey. The attack and feeding behaviors of naive predators (Podisus maculiventris stinkbugs) reared on control caterpillars (Manduca sexta) fed plain diet were compared to experienced predators reared on caterpillars fed tomato allelochemicals. Tomatine-fed prey were found more quickly by both naive and tomatine-experienced predators, and chlorogenic acid-experienced predators were more stimulated to begin searching for prey. However, experienced predators were less likely to attack both chlorogenic acidfed and tomatine-fed caterpillars than were naive predators. These results indicate that allelochemical-fed prey were easier for predators to locate, but allelochemical-containing prey often deterred predation by experienced predtors.     

Variation in foraging behavior facilitates resource partitioning in a polymorphic cichlid, Herichthys minckleyi

We examined foraging behavior (microhabitat use and feeding behavior) in a trophically polymorphic cichlid fish, Herichthys minckleyi, to address several questions regarding resource partitioning in this threatened species. These include: (1) do morphotypes demonstrate different foraging behaviors? (2) do individuals within a morphotype vary in their foraging behavior (e.g. are some individuals specialists, only using a subset of available resources, while other are generalists)? (3) do foraging behaviors vary between isolated pools? (4) do foraging behaviors vary across seasons? We quantified microhabitat use and feeding behavior for over 100 individuals (of two morphotypes) feeding freely in two isolated pools (populations) and across two seasons (winter and summer). We found differences in foraging behavior between morphotypes and individual specializations within morphotypes; i.e. some individuals specialize on certain food resources by using a few feeding behaviors within a subset of microhabitats, whereas others employ a range feeding behaviors across many microhabitats. Foraging behavior also varied between pools and across seasons. This spatial and temporal variation in foraging behavior and resource use may serve to maintain this polymorphism, as the relative fitness of the each morph may vary over space and time.     

Phenological influences on the utilization of woody plants by eland in semi-arid shrubland

Our study monitored the acceptability, shoot phenology and chemical content of karoid woody species over the seasonal cycle. Species favoured by eland as long as they retained leaves, were classified as palatable, while those neglected for part of the seasonal cycle, even though they retained leaves, were classified as unpalatable. Changes in the acceptability of unpalatable species over the seasonal cycle appeared to be related to changes in the proportion of young shoots on plants, as influenced by rainfall and temperature. These species were typically only favoured when they offered relatively high proportions of young shoots. Our study identified total fibre as the most important chemical factor influencing the acceptability of woody species to eland. The shoots of palatable species contained low fibre concentrations, while the shoots of unpalatable species were more variable in fibre content. When favoured, the shoots of unpalatable species typically had similar levels of fibre to palatable species, but when neglected, the shoots of unpalatable species generally had increased fibre levels. Eland have thrived since being introduced into our study area, which is dominated by microphyllous and leptophyllous woody species. We suggest that this is because eland are able to select a diet sufficiently low in fibre content.     

Constitutive exposure to the volatile methyl salicylate reduces per‐capita foraging efficiency of a generalist predator to learned prey associations

Understanding the factors that influence the ability of predators to find and kill herbivores is central to enhancing their impact on prey populations, but few studies have tested the impact of these factors on predation rates in realistic foraging environments. Using the tri‐trophic system consisting of tomato, Solanum lycopersicum L. (Solanaceae), hornworm caterpillars, Manduca sexta L. (Lepidoptera: Sphingidae), and the predaceous stink bug Podisus maculiventris (Say) (Hemiptera: Pentatomidae), we measured the effects of associative learning and plant volatile camouflage on predator behavior and foraging efficiency in field enclosures. To do so, we compared experienced vs. naive individuals under varying environmental contexts. Experienced predators were those with prior exposure to induced volatiles from the tomato–caterpillar association, whereas naive predators had not experienced tomato, only prey (caterpillars). We varied their environmental foraging matrix using either (1) tomato surrounded by basil (Ocimum basilicum L.; Lamiaceae) or (2) tomato exposed to the synthetic volatile, methyl salicylate (MeSA). We found that (1) experienced predators were more efficient than naive predators, capturing 28% more prey; (2) the tomato–basil combination did not affect predator–prey interactions; and (3) constitutive emission of synthetic MeSA caused a 22% reduction in P. maculiventris predation rate. These differences corresponded with distinct shifts in predator foraging; for example, experienced individuals were less stationary and exhibited unique behaviors such as stylet extension. Taken together, these results suggest that it is possible to improve the function of generalist predators in suppressing prey by coupling odors with food. However, constitutive emission of volatiles to attract natural enemies may ultimately camouflage neighboring plants, reducing the benefits of orientation to learned stimuli such as induced volatiles.     

Pupal warning color development in above-ground pupating species but cryptic color in ground-surface pupating species of the nine-spotted diurnal moths (Erebidae: Arctiinae: Syntomini)

Insects usually have cryptic colors to avoid detection by visually hunting predators. However, if the insects acquire toxic or repellent substances against predators, some of them develop conspicuous coloration to exhibit their unpalatability. Such warning colors allow insects to survive. In the nine-spotted diurnal moths (Erebidae: Arctiinae: Syntomini), we found the above-ground pupating species to have conspicuous colored pupae, but the ground-surface pupating species to have cryptic colored pupae. In this study, the relationships between unpalatability and coloration of these pupae are examined among three species of Amata and one species of Syntomoides. Pupae of the two species (A. germana and A. flava) are conspicuous in their color pattern with seven black dotted lines longitudinally on their pale-yellow bodies. These pupae are exposed to the aerial predators in a coarse silk mesh hanging from leaves and/or branches. The other two species (A. fortunei and S. imaon) pupate in spaces under stones, fallen twigs and leaves on the ground surface, and the pupae in a coarse silk cocoon is cryptic dark brown. Their pupation site selections are reproduced in the rearing glass vessels. Palatability assessment using lizards as a potential predator suggests that pupae of A. germana, A. flava and A. fortunei are unpalatable and the lizard's feeding response decreases with experience. However, pupae of S. imaon are all eaten (palatable). Finally, the possible evolutionary scenario of pupal colors of these four species is discussed in relation to pupation site selection and palatability.