Host Plant Specialization and Species Turnover of Caterpillars Among Hosts in the Brazilian Cerrado

Decrease in the species composition similarity of herbivore assemblages with increasing phylogenetic distance between host plants is a widespread pattern. Here we used data for caterpillars in the Brazilian Cerrado to investigate how the similarity in caterpillar species composition decreases as the taxonomic level and genetic distance (GD) of their host plants increases. In addition, we elucidate the plant taxonomic level that provides the greatest contribution to turnover in the caterpillar species composition among host taxa. Adult Lepidoptera were reared from caterpillars collected from 52 plants over 13 yr in the same area, with each host plant sampled for 1 yr. Most species were specialists, with 66 percent of genus specialists among the nonsingleton species. The similarity in caterpillar species composition across plant taxa decreased from host species to genera, and from host genera to orders. Above this level, the similarity was consistently low. The GD between plants explained 82 percent of the variation in the similarity of caterpillar species composition. The contribution of caterpillar species turnover among host orders from the same superorder and among host superorders from the same subclass explained 70 percent of the caterpillar species richness as a whole. Our results lend support to the view that most tropical caterpillars are host specialists. Our findings further indicate that the number of orders and superorders of plants provide the greatest contribution to the total caterpillar richness compared with all of the other host taxonomic levels combined. Abstract in Portuguese is available at http://www.blackwell‐synergy.com/loi/btp .     

Shelter-building caterpillars in the cerrado: seasonal variation in relative abundance, parasitism, and the influence of extra-floral nectaries

Caterpillar shelters provide protection against desiccation and natural enemies, whereas extra-floral nectaries (EFNs) may be an anti-herbivore adaptation that reduces herbivore abundance by attracting predators and parasites. We used a large, long-term dataset for caterpillars found in the Brazilian cerrado to examine temporal variations in the relative abundance of shelter-building caterpillars and exposed caterpillars, and to determine how much variation depends on the season and the presence of EFNs on host plants. We also compared the patterns of parasitism between sheltered and exposed caterpillars, between seasons, and between different host plants. The cerrado has a marked dry season, and its vegetation is a mixture of mostly deciduous shrubs and trees. Leaf production occurs mainly during the rainy season, and many plant species bear EFNs. Our results show that 60?% of cerrado caterpillars build shelters. These caterpillars were found to be proportionally more abundant during the dry season and less parasitized than exposed ones. The proportion of caterpillars building shelters was highest on plants with new leaves (functional EFNs), and parasitism of caterpillars on these plants was higher. Even though our study includes a taxonomically diverse suite of caterpillars that build many different types of shelter and a diverse set of plants and EFN types, our results suggest that EFNs play an important role in structuring caterpillar assemblages in the cerrado, and that the prolific use of shelters by caterpillars may be a result of their effectiveness in protecting caterpillars from natural enemies and desiccation.     

No tree an island: the plant–caterpillar food web of a secondary rain forest in New Guinea

We characterized a plant–caterpillar food web from secondary vegetation in a New Guinean rain forest that included 63 plant species (87.5% of the total basal area), 546 Lepidoptera species and 1679 trophic links between them. The strongest 14 associations involved 50% of all individual caterpillars while some links were extremely rare. A caterpillar randomly picked from the vegetation will, with ≥ 50% probability, (1) feed on one to three host plants (of the 63 studied), (2) feed on < 20% of local plant biomass and (3) have ≥ 90% of population concentrated on a single host plant species. Generalist species were quantitatively unimportant. Caterpillar assemblages on locally monotypic plant genera were distinct, while sympatric congeneric hosts shared many caterpillar species. The partitioning of the plant–caterpillar food web thus depends on the composition of the vegetation. In secondary forest the predominant plant genera were locally monotypic and supported locally isolated caterpillar assemblages.     

Cascading effects of host size and host plant species on parasitoid resource allocation

1. The bottom‐up factors that determine parasitoid host use are an important area of research in insect ecology. Host size is likely to be a primary cue for foraging parasitoids due to its potential influence on offspring development time, the risk of multiparasitism, and host immunocompetence. Host size is mediated in part by host‐plant traits that influence herbivore growth and potentially affect a herbivore's quality as a host for parasitoids. 2. Here, we tested how caterpillar host size and host plant species influence adult fly parasitoid size and whether host size influences wasp parasitoid sex allocation. We measured the hind tibia lengths and determined the sex of wasp and fly parasitoids reared from 11 common host species of polyphagous caterpillars (Limacodidae) that were in turn reared on foliage of seven different host plant species. 3. We also tested how host caterpillar species, host caterpillar size, and host and parasitoid phenology affect how the parasitoid community partitions host resources. We found evidence that parasitoids primarily partition their shared hosts based on size, but not by host species or phenology. One index of specialisation (d′) supports our observation that these parasitoids are quite generalised within the Limacodidae. In general, wasps were reared from caterpillars collected in early instars, while flies were reared from caterpillars collected in late instars. Furthermore, for at least one species of solitary wasp, host size influenced sex allocation of offspring by ovipositing females. 4. Host‐plant quality indirectly affected the size attained by a tachinid fly parasitoid through its direct effects on the size and performance of the caterpillar host. The host plants that resulted in the highest caterpillar host performance in the absence of enemies also yielded the largest parasitoid flies, which suggests that host plant quality can cascade up to influence the third trophic level.     

Biology and occurrence of Inga Busk species (Lepidoptera: Oecophoridae) on Cerrado host plants

We sampled Inga Busk species caterpillars weekly in the cerrado on 15 plants of Diospyros burchellii Hern. (Ebenaceae) from January 2002 to December 2003, on 30 plants of Caryocar brasiliense (Caryocaraceae) from July 2003 to June 2004, and since 1991 on several other plant species. In total we found 15 species of Inga on cerrado host plants. Nine species were very rare, with only one to five adults reared. The other six species occurred throughout the year, with higher abundance during the dry season, from May to July, coinciding with overall peaks of caterpillar abundance in the cerrado. Caterpillars of the genus Inga build shelters by tying and lining two mature or old leaves with silk and frass, where they rest and develop (a common habit found in Oecophorinae). The final instar builds a special envelope inside the leaf shelter, where it will complete the larval stage and pupate. The species are very difficult to distinguish in the immature stages. External features were useful in identifying only four species: I. haemataula (Meyrick), I. phaecrossa (Meyrick), I. ancorata (Walsingham), and I. corystes (Meyrick). These four species are polyphagous and have wide geographical distributions. In this paper we provide information on the natural history and host plants of six Inga species common on cerrado host plants, for which there are no reports in the literature.     

Behavioural ecology of defence in a risky environment: caterpillars versus ants in a Neotropical savanna

1. Predatory ants may reduce infestation by herbivorous insects, and slow‐moving Lepidopteran larvae are often vulnerable on foliage. We investigate whether caterpillars with morphological or behavioural defences have decreased risk of falling prey to ants, and if defence traits mediate host plant use in ant‐rich cerrado savanna. 2. Caterpillars were surveyed in four cerrado localities in southeast Brazil (70–460 km apart). The efficacy of caterpillar defensive traits against predation by two common ant species (Camponotus crassus, C. renggeri) was assessed through experimental trials using caterpillars of different species and captive ant colonies. 3. Although ant presence can reduce caterpillar infestation, the ants' predatory effects depend on caterpillar defence traits. Shelter construction and morphological defences can prevent ant attacks (primary defence), but once exposed or discovered by ants, caterpillars rely on their size and/or behaviour to survive (secondary defence). 4. Defence efficiency depends on ant identity: C. renggeri was more aggressive and lethal to caterpillars than C. crassus. Caterpillars without morphological defences or inside open shelters were found on plants with decreased ant numbers. No unsheltered caterpillar was found on plants with extrafloral nectaries (EFNs). Caterpillars using EFN‐bearing plants lived in closed shelters or presented morphological defences (hairs, spines), and were less frequently attacked by ants during trials. 5. The efficiency of defences against ants is thus crucial for caterpillar survival and determines host plant use by lepidopterans in cerrado. Our study highlights the effect of EFN‐mediated ant‐plant interactions on host plant use by insect herbivores, emphasizing the importance of a tritrophic viewpoint in risky environments.     

Traditional Regulation of Edible Caterpillar Exploitation in the Kopa Area of Mpika District in Northern Zambia

The Traditional Ecological Knowledge (TEK) of the Bisa people of northern Zambia on species, life cycles and host plants of the caterpillars they exploit for food and for household income generation, and the traditional control of caterpillar harvesting, were investigated through a household survey. The accessed indigenous knowledge on caterpillar biology was validated through a forest survey, caterpillar collections and identifications. Eight species of caterpillars were harvested from the surrounding miombo woodlands. Their life systems and host plants were well understood by members of local communities and this knoweldge was communicated amongst them orally. Popular commercial species were Gynanisa maya Strand and Gonimbrasia zambesina Walker. Over 20 miombo tree species hosted the two species but the mean numbers of the caterpillars on Julbernadia paniculata Troupin were significantly larger than those on other host plants (p < 0.05), indicating that J. paniculata was probably the main host plant of the two species. Traditional regulation of caterpillar harvesting involved: (i) monitoring for edible caterpillar development and abundance and for changes in caterpillar habitats, (ii) protection of host plants and moth eggs against late bush fires, through use of traditional fire technology, and (iii) temporal restriction of edible caterpillar harvesting. The possibility of the Zambian Government promoting caterpillar harvesting as an economic incentive to the Bisa people to conserve both this renewable edible caterpillar natural resource and their environment is discussed.     

An altitudinal comparison of caterpillar (Lepidoptera) assemblages on Ficus trees in Papua New Guinea

Aim This analysis of caterpillar (Lepidoptera) beta‐diversity between tropical lowlands and highlands attempts to separate the effects of between‐site (1) turnover of herbivore species on particular host plants, (2) changes in host use by herbivores, and (3) turnover of plant species on changes in herbivore assemblages. Location Two rain forest areas 130 km and 1700 altitudinal metres apart were studied in Papua New Guinea: one in the lowlands (100 m a.s.l.) on the northern coast of the island and one in the central New Guinean cordillera at 1800 m a.s.l. Methods The analysis is based on caterpillar feeding records obtained by quantitative sampling and rearing of caterpillars from four Ficus species studied in the mountains and 21 Ficus species and 62 plant species from other genera and families studied in the lowlands, including three Ficus species studied in both areas. Results Only 17% of species feeding on Ficus in the highlands also occurred in the lowlands. These species represented 1–46% of individuals in caterpillar assemblages on particular Ficus hosts. Widespread species included both Ficus specialists and generalists feeding on numerous plant families. Some of the Ficus specialists changed their preferred host species with altitude. High species turnover was not explained by changes in the species composition of host plants with altitude as lowland and montane assemblages feeding on the same Ficus species showed high turnover. Despite the rarity of widespread caterpillars, the lowland and montane Ficus assemblages were remarkably similar in their dominance structure, species richness, host specificity, generic composition and familial composition. Main conclusions Ficus‐feeding Lepidoptera assemblages between tropical lowlands and highlands are characterized by substantial species turnover not explained by altitudinal changes in the composition of the vegetation. Further, species‐rich plant genera can support caterpillar assemblages with relatively low beta‐diversity compared with species‐poor genera as caterpillars can switch their host preferences from one congeneric host species to another along an altitudinal gradient. Closely related plant species can thus represent a broad, continuously distributed resource along such gradients.     

Folivore caterpillars on Roupala montana Aubl. (Proteaceae) in cerrado sensu stricto

Richness of lepidopteran species in the cerrado is high. The confirmation of this richness is based on adult records but knowledge of larvae-host plants interactions is still incipient. The main purpose of this work was to identify folivorous caterpillar species on Roupala montana Aubl. in areas of a Brazilian cerrado sensu stricto, their dietary range, and the relative age of the consumed leaves richness. Three data sets, collected from 1991 to 2004 were used in this study. All caterpillars found on the host plants in the field were collected and reared in the laboratory. Sixty-two lepidopteran species from 22 families were recorded; they were found feeding on new (8%) and mature (92%) leaves of R. montana. Cerconota sciaphilina (Zeller) (Elachistidae), two unidentified Gracillariidae species and, one species of Gelechiidae fed only on new leaves. These species showed a short life cycle, which was very syncronized with the host plant foliar phenology. Among the species feeding on mature leaves, 36 were considered polyphagous and, these showed a large variation in the use of the food resource. Twenty-six species were found only on R. montana, 58% were very rare, a character that difficults the analysis of their dietary range. The monophagous species on R. montana were: Chlamydastisplatyspora (Meyrick) (Elachistidae), Stenoma cathosiota Meyrick (Elachistidae), Idalus prop. sublineata (Rothschild) (Arctiidae), and Eomichla sp. (Oecophoridae).     

Does a polyphagous caterpillar have the same gut microbiota when feeding on different species of food plants?

We used classical culture techniques to explore gut bacteria and changes associated with dietary change in the highly polyphagous, tropical caterpillar Automeris zugana (Saturniidae). Fifty-five third instar wild-caught sibs feeding on Annona purpurea (Annonaceae) in the Area de Conservación Guanacaste (ACG) in northwestern Costa Rica were divided into eight groups. Each of seven groups was reared to the ultimate instar on another species of food plant normally used by A. zugana. Some pupae were also analyzed for the presence of bacteria. Aerobic bacterial cultures were obtained from all 33 caterpillar guts and the eight pupae inventoried. There was no clear pattern in species composition of cultivated bacteria among the eight diets, and each caterpillar on a given food plant carried only a small fraction of the total set of species isolated from the set of caterpillars feeding on that food plant. Taken as a whole, the larvae and pupae contained 22 species of cultivable bacteria in 12 genera. Enterobacter, present in 81.8% of the samples, was the genus most frequently isolated from the caterpillars, followed by Micrococcus and Bacillus. Bacillus thuringiensis was isolated from 30.3% of the dissected caterpillars, but found in caterpillars feeding on only half of the species of food plants.     

Host plant preference in the protected myrmecophilous Transylvanian Blue (<Emphasis Type="Italic">Pseudophilotes bavius hungarica</Emphasis>) butterfly (Lepidoptera: Lycaenidae) and its relationship with potential ant partners

When selecting specific host plants, caterpillars of many lycaenid butterflies, such as the protected Pseudophilotes bavius hungarica, are known to engage in various interactions with ants, which help them survive. Although P. bavius is a protected species, data about its host plant selection is very scarce, and little information is available on its myrmecophilous relationships. Our aim was to identify the host plant characteristics that determine the occurrence of the caterpillar and to clarify the specificity of its myrmecophily. We conducted a series of field surveys regarding host plant characteristics. Laboratory experiments were carried out to investigate the nature of interactions between the caterpillar and its potential ant partners. Control experiments involving non-visiting ants were also performed. On the basis of our findings, the physical characteristics of host plants do not seem to influence host plant choice, but the absence of aphids and the presence of different ant species proved important. According to the results of behavioural assays, neutral reactions to the caterpillars were recorded in the case of ant species that regularly visited the host plant (Lasius paralienus, Camponotus aethiops), in contrast to Tapinoma subboreale, which was not observed at all on the host plants and which behaved aggressively towards the larvae. Therefore, the caterpillar is expected to show a certain ant host selectivity. The study constitutes an essential contribution to our knowledge of the natural history of a protected butterfly species, which can be used as a basis for more appropriate management strategies, while also shedding light on aspects of myrmecophilous relationships in Lycaenidae in general.     

The interaction between host and host plant influences the oviposition and performance of a generalist ectoparasitoid

The successful development of parasitoids of herbivores depends on the quality of their host, which is often affected by the host plant. Therefore, a parasitoid’s oviposition decisions will directly depend on the host, but also on plant quality. Here, we investigated the direct effects of host species and the indirect effects of the host’s food plant on the oviposition decisions and performance of the gregarious ectoparasitoid Euplectrus platyhypenae Howard (Hymenoptera: Eulophidae). With a series of no‐choice experiments, we determined the oviposition and performance of the parasitoid on: (1) two caterpillar species, fall armyworm, Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae), and velvet armyworm, Spodoptera latifascia Walker, reared on maize (Zea mays L., Poaceae), (2) the same caterpillars reared on maize, bean (Phaseolus vulgaris L., Fabaceae), or squash (Cucurbita pepo L., Cucurbitaceae) leaves, and (3) S. latifascia caterpillars reared on leaves of wild and cultivated lima bean, Phaseolus lunatus L. All these insects and plants originate from Mesoamerica where they have coexisted for thousands of years in the traditional agricultural system known as Milpa in which maize, beans, and squash are planted together. We found that the preferred and best combination of host and host plant for parasitoid performance was S. frugiperda on maize. Parasitoids laid larger clutches, had higher survival, and more females and larger adults emerged from S. frugiperda reared on maize. However, when both caterpillar species were reared on squash, S. latifascia was the better host. Contrary to the literature, S. frugiperda was not able to develop on bean plants. Results from the lima bean experiment showed that parasitoid performance was best when S. latifascia was reared on leaves of cultivated compared to wild lima bean. These findings are discussed in the context of mixed cropping in which the ability of generalist parasitoids to switch among hosts and host plant species could be advantageous for pest management.     

Chemical convergence between a guild of facultative myrmecophilous caterpillars and host plants

1. Ants exert strong selective pressure on herbivorous insects, although some caterpillars can live in symbiosis with them using chemical defensive strategies.
2. We investigated the adaptive resemblance of cuticular hydrocarbons (CHCs) in multitrophic systems involving a guild of facultative myrmecophilous caterpillar species (Lepidoptera: Lycaenidae), tending ants (Hymenoptera: Formicidae), and host plants from three families. We hypothesised that the CHCs of the caterpillars would resemble those of their host plants (chemical camouflage).
3. We analysed CHCs using gas chromatography/mass spectrometry. Morisita's similarity index (SI) was used to compare CHC profiles of caterpillar species with different types of ant associations (commensal or mutualistic), ants, and host plants.
4. We found strong convergence between caterpillars' CHCs and plants, especially for commensal species that do not provide secretion rewards for ants. Moreover, we found unexpected chemical convergence among mutualistic (trophobiotic) caterpillar species that offer caloric reward secretions to ants.
5. These results show that the studied caterpillars acquire CHCs through their diet and that they vary according to host plant species and type of ant association (commensalism or mutualism). This ‘chemical camouflage’ of myrmecophilous caterpillars may have arisen as a defensive strategy allowing coexistence with ants on plants, whereas ‘chemical conspicuousness’ may have evolved in the context of honest signalling between mutualistic partners.
6. We suggest the existence of chemical mimicry among myrmecophilous species, especially between mutualistic caterpillars. Cuticular chemical mixtures can play a key adaptive role in decreasing ant attacks and increasing caterpillar survival in multimodal sensory systems.

     

Temporal and spatial variation of Stenoma cathosiota Meyrick (Lepidoptera: Elachistidae) caterpillar abundance in the cerrado of Brasilia, Brazil

The caterpillars of Stenoma cathosiota Meyrick feed on Roupala montana Aubl. (Proteaceae) in the cerrado of the Distrito Federal, Brazil. They construct shelters by joining leaves of the plant where they feed and pupate. The caterpillars are parasitized by a wasp (Hymenoptera: Brachonidae), which emerges from the pupae. Caterpillar abundance and parasitism frequency were associated in an area of frequently burned cerrado (biennial fire) and in another area that burns sporadically (1987 and 1994). For S. cathosiota, the variation among years in a single area, with sporadic fires, was greater than the variation among areas with different fire regimes. Caterpillar abundance among years was significantly different in the area that burns sporadically (chi2 = 24.06; df. = 1; P = 0.000). However, there were no significant differences on caterpillar abundance between areas for the same period (chi2 = 3.45; df. = 1; P = 0.063). Parasitism frequency was high, reaching 29% of the collected caterpillars, and did not differ among areas. The great temporal variation in abundance of lepidopteran caterpillars in the cerrado makes it difficult to determine the effects that fire exerts over this fauna.     

Impact of plant architecture versus leaf quality on attack by leaf-tying caterpillars on five oak species

Because shelter-building herbivorous insect species often consider structural features of their host plants in selecting construction sites, their probability of attack is likely to be a function of some combination of plant architectural traits and leaf quality factors. We tested the hypothesis that plant architecture, in the form of the number of touching leaves, influences interspecific variation in attack by leaf-tying caterpillars in five species of sympatric Missouri oaks (Quercus). We compared colonization on control branches, in which both architecture and leaf quality were potentially important, with colonization on experimental branches for which we controlled for the effects of architecture by creating equal numbers of artificial ties. Colonization of artificial ties was highly correlated with natural colonization on neighboring control branches, suggesting that leaf quality factors and not architecture influenced interspecific variation in attack by leaf-tying caterpillars. Of the leaf quality factors measured (water, protein-binding capacity, nitrogen, specific leaf area, pubescence, and toughness), nitrogen was the most explanatory. With the exception of white oak, natural leaf tie colonization was positively correlated with nitrogen availability (ratio of nitrogen to protein-binding capacity), and negatively correlated with protein-binding capacity of leaf extracts. Both host plant species and subgenus oak influenced the community composition of leaf-tying caterpillars and the non-tying symbionts colonizing the ties. Host plant differences in leaf nitrogen content were positively correlated with pupal weight of one of two caterpillar species reared on all five host plant species. Thus, interspecific differences in nitrogen, nitrogen availability, and protein-binding capacity of leaf extracts are the best predictors at this time of interspecific differences in attack by leaf-tying caterpillars, in turn affecting their success on individual host plants in the laboratory.     

Parasitoid Wasps in Flower Heads of Asteraceae in the Brazilian Cerrado: Taxonomical Composition and Determinants of Diversity

This study provides the first survey of the parasitoid fauna reared in flower heads of Asteraceae in the Brazilian cerrado. We investigated the relative importance of herbivore richness and plant species commonness to differences in parasitoid species richness among the plant species. A total of 15,372 specimens from 192 morphospecies belonging to 103 genera of Hymenoptera were reared from the flower heads of 74 Asteraceae species. Chalcidoidea and Ichneumonoidea were the most common superfamilies, with Eulophidae and Braconidae as the main families of parasitoid wasps. Singletons and doubletons accounted for 45% of total parasitoid species richness. The number of parasitoid species per plant species ranged from 1 to 67, and the variation in parasitoid species richness among plants was mainly explained by the number of sites in which the plants were recorded. This study shows that there is a highly diversified fauna of Hymenoptera parasitoids associated with flower heads of Asteraceae in the Brazilian cerrado. Our findings suggest that the accumulation of parasitoid species on plants is mainly determined by the regional commonness of plant species rather than the number of herbivore species associated with the plants.     

Plant quality and local adaptation undermine relocation in a bog specialist butterfly

The butterfly Boloria aquilonaris is a specialist of oligotrophic ecosystems. Population viability analysis predicted the species to be stable in Belgium and to collapse in the Netherlands with reduced host plant quality expected to drive species decline in the latter. We tested this hypothesis by rearing B. aquilonaris caterpillars from Belgian and Dutch sites on host plants (the cranberry, Vaccinium oxycoccos). Dutch plant quality was lower than Belgian one conferring lower caterpillar growth rate and survival. Reintroduction and/or supplementation may be necessary to ensure the viability of the species in the Netherlands, but some traits may have been selected solely in Dutch caterpillars to cope with gradual changes in host plant quality. To test this hypothesis, the performance of Belgian and Dutch caterpillars fed with plants from both countries were compared. Dutch caterpillars performed well on both plant qualities, whereas Belgian caterpillars could not switch to lower quality plants. This can be considered as an environmentally induced plastic response of caterpillars and/or a local adaptation to plant quality, which precludes the use of Belgian individuals as a unique solution for strengthening Dutch populations. More generally, these results stress that the relevance of local adaptation in selecting source populations for relocation may be as important as restoring habitat quality.     

Comparison of midgut bacterial diversity in tropical caterpillars (Lepidoptera: Saturniidae) fed on different diets

As primary consumers of foliage, caterpillars play essential roles in shaping the trophic structure of tropical forests. The caterpillar midgut is specialized in plant tissue processing; its pH is exceptionally alkaline and contains high concentrations of toxic compounds derived from the ingested plant material (secondary compounds or allelochemicals) and from the insect itself. The midgut, therefore, represents an extreme environment for microbial life. Isolates from different bacterial taxa have been recovered from caterpillar midguts, but little is known about the impact of these microorganisms on caterpillar biology. Our long-term goals are to identify midgut symbionts and to investigate their functions. As a first step, different diet formulations were evaluated for rearing two species of tropical saturniid caterpillars. Using the polymerase chain reaction (PCR) with primers hybridizing broadly to sequences from the bacterial domain, 16S rRNA gene libraries were constructed with midgut DNA extracted from caterpillars reared on different diets. Amplified rDNA restriction analysis indicated that bacterial sequences recovered from the midguts of caterpillars fed on foliage were more diverse than those from caterpillars fed on artificial diet. Sequences related to Methylobacterium sp., Bradyrhizobium sp., and Propionibacterium sp. were detected in all caterpillar libraries regardless of diet, but were not detected in a library constructed from the diet itself. Furthermore, libraries constructed with DNA recovered from surface-sterilized eggs indicated potential for vertical transmission of midgut symbionts. Taken together, these results suggest that microorganisms associated with the tropical caterpillar midgut may engage in symbiotic interactions with these ecologically important insects.     

Bacillus thuringiensis in caterpillars and associated materials collected from protected tropical forests in northwestern Costa Rica

Bacillus thuringiensis (Bt) synthesizes crystalline inclusions that are toxic to caterpillars (Lepidoptera) and other orders of invertebrates. Materials associated with 37 caterpillars from 16 species, collected while feeding on 15 different species of host plants in dry, cloud and rain forests located in the Area de Conservación Guanacaste in northwestern Costa Rica, were examined for the presence of Bt. From a total of 101 derived samples, 25 Bt isolates were cultured: 56% from host plant leaves, 8% from caterpillar guts and 36% from caterpillar fecal pellets. Bt was isolated from at least one sample in 38% of the systems constituted by the food plant, gut and fecal pellets corresponding to a single caterpillar. Four different morphologies of crystalline inclusions were observed, with bipyramidal and irregular crystal morphologies being the most prevalent.     

Dietary specialization and the effects of plant species on potential multitrophic interactions of three species of nymphaline caterpillars

The diet breadth of insect herbivores influences their response to variation in plant quality, and these bitrophic interactions have implications for the higher‐level trophic interactions between herbivores and their natural enemies. In this comparative study, we examined the role of host plant species and plant secondary chemistry on the potential interactions between three species of nymphaline caterpillars and their natural enemies. The caterpillar species (all Lepidoptera: Nymphalidae) varied in their degree of specialization: the buckeye, Junonia coenia Hübner, is a specialist on plants that contain iridoid glycosides (IGs); the white peacock, Anartia jatrophae L., feeds on plants in five families, some of which contain IGs and some of which do not; and the painted lady, Vanessa cardui L., is a generalist, feeding on plants in at least 15 families. Each species was reared on leaves of an introduced host plant, Plantago lanceolata L. (Plantaginaceae), which produces two IGs, aucubin and catalpol, and on another plant species that is a common host plant. These alternate host plants were Plantago major L. (Plantaginaceae) for J. coenia, Bacopa monnieri (L.) Pennell (Plantaginaceae) for A. jatrophae, and Malva parviflora L. (Malvaceae) for V. cardui. We examined growth, sequestration, and immune response of these caterpillars on the different host plant species. Junonia coenia developed more rapidly and sequestered higher IG concentrations when reared on P. lanceolata, whereas both other species grew more slowly on P. lanceolata. Host plant did not influence immune response of J. coenia or A. jatrophae, whereas V. cardui immune response was weaker when reared on P. lanceolata. Junonia coenia was most efficient at IG sequestration and A. jatrophae was least efficient, when all three species were reared on P. lanceolata. These results indicate that diet breadth may play an important role in structuring tritrophic interactions, and this role should be further explored.