Microbiomes of a specialist caterpillar are consistent across different habitats but also resemble the local soil microbial communities

Background Insect-associated microorganisms can provide a wide range of benefits to their host, but insect dependency on these microbes varies greatly. The origin and functionality of insect microbiomes is not well understood. Many caterpillars can harbor symbionts in their gut that impact host metabolism, nutrient uptake and pathogen protection. Despite our lack of knowledge on the ecological factors driving microbiome assemblages of wild caterpillars, they seem to be highly variable and influenced by diet and environment. Several recent studies have shown that shoot-feeding caterpillars acquire part of their microbiome from the soil. Here, we examine microbiomes of a monophagous caterpillar (Tyria jacobaeae) collected from their natural host plant (Jacobaea vulgaris) growing in three different environments: coastal dunes, natural inland grasslands and riverine grasslands, and compare the bacterial communities of the wild caterpillars to those of soil samples collected from underneath each of the host plants from which the caterpillars were collected. Results The microbiomes of the caterpillars were dominated by Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes. Only 5% of the total bacterial diversity represented 86.2% of the total caterpillar’s microbiome. Interestingly, we found a high consistency of dominant bacteria within the family Burkholderiaceae in all caterpillar samples across the three habitats. There was one amplicon sequence variant belonging to the genus Ralstonia that represented on average 53% of total community composition across all caterpillars. On average, one quarter of the caterpillar microbiome was shared with the soil. Conclusions We found that the monophagous caterpillars collected from fields located more than 100 km apart were all dominated by a single Ralstonia. The remainder of the bacterial communities that were present resembled the local microbial communities in the soil in which the host plant was growing. Our findings provide an example of a caterpillar that has just a few key associated bacteria, but that also contains a community of low abundant bacteria characteristic of soil communities.

Biodiversity of beet webworm microsporidia in Eurasia

The beet webworm Loxostege sticticalis (LS) has eruptive type of population dynamics and high migratory activity. The LS outbreaks are therefore difficult to predict and the pest belongs to the category of highly dangerous pests. However, during periods of depressions this insect is not observed within the most of its range and is very susceptible to infection by pathogens, including various species of microsporidia, some of which are not specific parasites of the order Lepidoptera. The distribution of LS microsporidia in Eurasia is quite extensive. During the study period of LS from 2003 to 2019, we have found 6 species of microsporidia. The parasite list includes not only species known for Lepidoptera such as Nosema sp. and Vairimorpha thomsoni, but also Vairimorpha (Nosema) ceranae as the typical pathogen from Apis mellifera, as well as Endoreticulatus cf poecilimonae, a pathogen similar to Endoreticulatus poecilimonae from Poecilimon thoracicus. Moreover, two isolates from the genus Tubulinosema identified in LS belong to the group of parasites with a very wide host range, including humans. In laboratory experiments, LS proved high sensitivity to microsporidia N. pyrausta from Ostrinia nubilalis and N. tyriae from Tyria jacobaeae. Its susceptibility to Paranosema locustae from Locusta migratoria has also been discovered.

Distance-dependent aposematism and camouflage in the cinnabar moth caterpillar ( Tyria jacobaeae , Erebidae)

Defended prey often use distinctive, conspicuous, colours to advertise their unprofitability to potential predators (aposematism). These warning signals are frequently made up of salient, high contrast, stripes which have been hypothesized to increase the speed and accuracy of predator avoidance learning. Limitations in predator visual acuity, however, mean that these patterns cannot be resolved when viewed from a distance, and adjacent patches of colour will blend together (pattern blending). We investigated how saliency changes at different viewing distances in the toxic and brightly coloured cinnabar moth caterpillar ( Tyria jacobaeae ). We found that although the caterpillars' orange-and-black stripes are highly salient at close range, when viewed from a distance the colours blend together to match closely those of the background. Cinnabar caterpillars therefore produce a distance-dependent signal combining salient aposematism with targeted background matching camouflage, without necessarily compromising the size or saturation of their aposematic signal.

Predator Interference with the Cinnabar Moth (Tyria jacobaeae) for the Biological Control of Tansy Ragwort (Senecio jacobaea)

Quantification of interference with biological control agents can provide support for anecdotal claims of success or failure of agent establishment and efficacy. This study was initiated because of observed predation of cinnabar moth larvae by carpenter ants when releasing larvae for the control of tansy ragwort, an invasive plant in Montana. Biotic and abiotic factors were compared among three sites with historically variable moth population establishment. Two experiments were developed to (1) observe and document insect activity, predation, or disappearance on tansy ragwort stems either protected or accessible to ants; and (2) quantify the effects of ant exclusion on herbivory of tansy ragwort. Site comparisons indicated that ant colony density was highest at the driest of three sites, and, interestingly, no ant colonies were detected at the site with higher observed numbers of moth larvae and adults and lower densities of tansy ragwort. Available substrate (logs and stumps) for ant colonization did not differ between the three sites. In the ant exclusion experiments, a larger number of larvae were missing on plants accessible to ants (63%) compared with plants where ants were excluded (39%) after 36 h. Direct observation of predation of larvae by carpenter ants accounted for 9% of missing larvae on stems accessible to ants. Larvae were able to consume 81% of original flowers or buds on ant-excluded stems, compared with 18% consumption on ant-accessible stems, suggesting that ant predation could limit the efficacy of cinnabar moth larvae. These results provide one of many possible explanations for the anecdotal observations of large, persistent populations of cinnabar moths in moist areas. This work emphasizes the importance of post-release observation and monitoring to detect and, ideally, quantify factors to support anecdotal perceptions regarding the fate and subsequent efficacy of insect biological-control agents.

Nontarget species selection for host range testing of Cotesia urabae

Classical biological control is being attempted for Uraba lugens (Lepidoptera Noctuidae Nolinae) an Australian eucalypt pest established in New Zealand The Australian solitary larval endoparasitoid Cotesia urabae (Hymenoptera Braconidae) is the most promising agent under investigation A nontarget species list was compiled for host range testing The endemic species Celama parvitis is the sole New Zealand representative of the Nolinae and was highest priority The next most closely related subfamily is the Arctiinae of which New Zealand has four endemic species (Metacrias huttoni M erichrysa M strategica and Nyctemera annulata) and one introduced biological control agent (Tyria jacobaeae) The merits of including other more distantly related members of the Noctuidae and unrelated Lepidoptera filling a similar niche are discussed

Host range testing of a nucleopolyhedrovirus of the lightbrown apple moth Epiphyas postvittana

Epiphyas postvittana nucleopolyhedrovirus (EppoNPV) has considerable potential as a biocontrol agent or biopesticide for control of lightbrown apple moth Epiphyas postvittana a pest of horticultural crops in New Zealand and a market access problem in export fruit To obtain regulatory approval for EppoNPV in either role EppoNPV must not negatively impact on nontarget organisms In this study eight nontarget insect species from one hymenopteran and five lepidopteran families were inoculated with EppoNPV at high titre (109 PIB/ml) Larval survival growth rates pupation and pupal weights were measured and larvae examined for EppoNPV Minor differences in one parameter were found in Helicoverpa armigera and Cydia pomonella but no viral infection Growth and survival were compromised in virusfed individuals in only one species Tyria jacobaeae The majority of T jacobaeae larvae had high microsporidal infections and EppoNPV polyhedra were found in only one larva suggesting a very low likelihood of field infectivity

Safety in New Zealand weed biocontrol a nationwide survey for impacts on nontarget plants

The safety record of weed biocontrol was questioned recently when examples of damage to nontarget plants were reported overseas Until now systematic investigations of nontarget feeding have not been performed in New Zealand Results of surveys looking for evidence of nontarget damage caused by 20 biological control agents released against weeds in New Zealand are presented Most agents (16) are apparently hostspecific However two species (Tyria jacobaeae and Phytomyza vitalbae) were recorded attacking native plants although their attack was very minor and predictable from hostrange testing performed prior to release For two other species Bruchidius villosus and Cydia succedana nontarget attack was not predicted from hostrange testing Larval feeding by these species was confined to mainly weedy exotic plants that are closely related to their target plants The reliability of hostspecificity testing and overall safety record of weed biological control in New Zealand are discussed