Transgenic plants expressing immunosuppressive dsRNA improve entomopathogen efficacy against Spodoptera littoralis larvae

Transgenic plants that express double-stranded RNA (dsRNA) targeting vital insect genes have recently emerged as a valuable new tool for pest control. In this study, tobacco plants were transformed to produce dsRNA targeting Sl 102 gene that is involved in the immune response of Spodoptera littoralis larvae, a serious lepidopteran pest of several crops. Experimental larvae reared on transgenic tobacco lines showed (1) a strongly reduced level of Sl 102 transcripts, which was positively associated with food consumption; (2) a substantial impairment of the encapsulation response mediated by hemocytes; and (3) a marked increase in the susceptibility to Xentari™, a Bacillus thuringiensis-based insecticide. Importantly, this approach may allow a reduction in the doses of B. thuringiensis used for field applications and enhance its killing activity on mature larvae. The results obtained thus support the use of immunosuppressive RNAi plants to enhance the performance of microbial insecticides on lepidopteran larvae.

Tissue extraction from whole caterpillars v1

This protocol is designed for extracting DNA from Lepidopteran larvae but it will work on most animal tissue with some modifications to tube volumes and homogenisation settings.

Tachinid flies (Diptera: Tachinidae) reared from deciduous plant-feeding lepidopteran larvae at Hokkaido University Tomakomai Forest (Japan), with descriptions of three new species

Seven species of tachinid flies reared from herbivorous lepidopterans collected from the deciduous forest canopy at Hokkaido University Tomakomai Experimental Forest (0.2 ha plot), Hokkaido, Japan, are recorded and described: Blepharomyia brevicornis sp. nov. ex Erannis golda Djakonov (Geometridae), Catocala lara Bremer and Orthosia odiosa (Butler) (both Noctuidae); Ctenophorinia grisea Mesnil ex Himeropteryx miraculosa Staudinger (Notodontidae); Blepharipa carbonata (Mesnil) ex Marumba jankowskii (Oberthür) (Sphingidae); Cyzenis equifacialis sp. nov. ex Faristenia geminisignella Ponomarenko (Gelechiidae), Archips crataegana (Hübner), A. nigricauda Walshingham, Epinotia exquisitana Christoph and Pseudohedya gradana Christo (all Tortricidae); Cyzenis tetrasetosa sp. nov. ex Lomographa simplicior (Butler), Operophtera brunnea Nakajima and O. relegata Prout (Geometridae); Eulasiona zimini Mesnil ex Archips crataegana (Hübner), Pseudohedya gradana (Christoph), Rhopobota naevana (Hübner) and Rhopobota sp. (all Tortricidae); Panzeria sp. (nr. japonica Shima) ex Erannis golda Djakonov (Geometridae). The genus Eulasiona Townsend is moved to the subfamily Tachininae from its present position in the subfamily Dexiinae, and the female and puparium of Eulasiona zimini Mesnil are described for the first time. The parasitization rates and life habits of these tachinids are briefly discussed.

Infestation of Early- and Late-Flushing Trees by Spring Caterpillars: An Associational Effect of Neighbouring Trees

In temperate forests within Europe, early-flushing (EF) deciduous trees are often heavily infested by early spring leaf-eating Lepidoptera, while late-flushing (LF) trees are better protected in a phenological manner against such heavy infestations, as spring moth larvae begin to appear before their bud burst. The associational effects of EF trees on LF ones are only poorly known. We studied whether or not the infestation of LF trees by spring Lepidoptera can be affected by EF ones if they grow in the immediate vicinity. We compared spring assemblages of leaf-eating larvae of Lepidoptera on LF Quercus cerris L. with those on EF Q. pubescens Willd. in several microhabitats in Slovakia, Central Europe. Larvae were collected from mature and young trees. Mature trees sampled were growing: (1) in a closed-canopy forest; (2) in small groups; or (3) as a lone tree. Forest and tree groups are both constituted by oak species. Tree groups and lone trees were 20–50 m distant from forest edges. Young trees were growing (1) under mature Q. pubescens trees in a forest or (2) as a lone tree within forest gaps or near the edges. In the closed-canopy forest where LF trees (Q. cerris) were surrounded by EF ones (Q. pubescens), the caterpillars on mature LF trees were in abundance, almost as on mature EF ones. The species composition of larval assemblages on the two oak species was similar. In contrast, on small groups and on lone trees, the lepidopteran larvae were significantly less abundant on LF trees than EF ones. In the case of young trees, the abundance of larvae and their composition assemblages on both oaks were comparable in the forest. In the open habitat, LF trees were less infested by larvae than EF ones and the assemblages of moth larvae differed between the two. Our results reveal the effect (associational susceptibility) of EF trees on LF ones when growing in a close vicinity. It means that the phenological protection of LF trees may not be sufficient if they grow close to or are surrounded by EF ones.

Aphid Odorant-Binding Protein 9 Is Narrowly Tuned to Linear Alcohols and Aldehydes of Sixteen Carbon Atoms

Aphid odorant-binding protein 9 is almost exclusively expressed in antennae and is well conserved between different aphid species. In order to investigate its function, we have expressed this protein and measured ligand-binding affinities to a number of common natural compounds. The best ligands are long-chain aldehydes and alcohols, in particular Z9-hexadecenal and Z11-hexadecenal, as well as 1-hexadecanol and Z11-1-hexadecenol. A model of this protein indicated Lys37 as the residue that is likely to establish strong interactions with the ligands, probably a Schiff base with aldehydes and a hydrogen bond with alcohols. Indeed, when we replaced this lysine with a leucine, the mutated protein lost its affinity to both long aldehydes and alcohols, while the binding of other volatiles was unaffected. Long-chain linear alcohols are common products of molds and have been reported as aphid antifeedants. Corresponding aldehydes, instead, are major components of sex pheromones for several species of Lepidoptera. We speculate that aphids might use OBP9 to avoid mold-contaminated plants as well as competition with lepidopteran larvae.

A study of ladder-like silk foothold for the locomotion of bagworms

While walking on horizontal substrates, caterpillars skilfully engage all their legs, including three pairs of thoracic legs and a maximum of five pairs of prolegs, to move in a flexible wave-like motion. Such locomotory behaviours, represented by ‘crawling’ and ‘inching’ motions, have widely inspired the development of locomotion systems in soft robotics. However, bagworms are unable to use their prolegs for walking because these are always accommodated in a portable bag; thus, they are unable to walk using such general locomotory behaviours. Indeed, how they walk with only three pairs of thoracic legs is unknown at present. In this study, we show that bagworms construct a ladder-like foothold using their silk to walk without using prolegs. This enables them to walk not only on horizontal floor surfaces but also on wall and ceiling surfaces, even those with slippery or smooth surfaces. They construct the foothold by spinning a continuous silk thread in a zigzag manner and controlling the discharge of adhesive to attach the folded parts of the silk to a substrate. Discovery of this elaborate silk utilisation technique offers fresh insights into the diversity of silk use in lepidopteran larvae and provides potential designs for robot locomotion systems.

Comparison of Silks from Pseudoips prasinana and Bombyx mori Shows Molecular Convergence in Fibroin Heavy Chains but Large Differences in Other Silk Components

Many lepidopteran larvae produce silk feeding shelters and cocoons to protect themselves and the developing pupa. As caterpillars evolved, the quality of the silk, shape of the cocoon, and techniques in forming and leaving the cocoon underwent a number of changes. The silk of Pseudoips prasinana has previously been studied using X-ray analysis and classified in the same category as that of Bombyx mori, suggesting that silks of both species have similar properties despite their considerable phylogenetic distance. In the present study, we examined P. prasinana silk using ‘omics’ technology, including silk gland RNA sequencing (RNA-seq) and a mass spectrometry-based proteomic analysis of cocoon proteins. We found that although the central repetitive amino acid sequences encoding crystalline domains of fibroin heavy chain molecules are almost identical in both species, the resulting fibers exhibit quite different mechanical properties. Our results suggest that these differences are most probably due to the higher content of fibrohexamerin and fibrohexamerin-like molecules in P. prasinana silk. Furthermore, we show that whilst P. prasinana cocoons are predominantly made of silk similar to that of other Lepidoptera, they also contain a second, minor silk type, which is present only at the escape valve.