Effects of age and food source on secondary chemistry of larvae of Lymantria species (Lepidoptera: Lymantriidae).

Haemolymph and osmeterial secretions of caterpillars of Lymantria monacha (Linnaeus) and L. concolor Walker were analysed by gas chromatography/mass spectrometry for low molecular weight secondary metabolites. The similarities of their chemical compositions were determined by means of cluster analysis techniques in order to characterize possible chemical variations related to developmental stage or food of the larvae. For this purpose, two dissimilarity coefficients (Euclidean distances, Canberra metrics) and four clustering methods (UPGMA, WPGMA, WPGMC, single linkage) were combined. The patterns of secondary compounds obtained from the haemolymph and osmeterial secretions studied did not differ statistically significantly between two groups of L. monacha larvae fed with either larch, Larix decidua Mil., or Norway spruce, Picea abies (L.), indicating no relevant influence of plant chemistry. However, haemolymph of penultimate instar larvae of L. concolor fed on Rhododendron contained a mixture of compounds differing statistically significantly from that of last instar caterpillars. The total compositions of the corresponding gland secretions were statistically identical though the presence/amounts of individual compounds varied. This suggested that the haemolymph composition reflected changing physiological requirements of the successive instars, whereas the composition of the defensive mixtures remained comparatively constant, possibly due to a constant spectrum of potential enemies. A more pronounced age-dependence of larval chemistry was shown by a similar analysis of data from various developmental stages of L. dispar (Linnaeus) and one of its food plants. This analysis suggested plant composition affected the secondary chemistry of early larval instars of L. dispar. The results are discussed in terms of the roles of secondary metabolites in defence against natural enemies.

Biodegradation and transfer of ingested 2,4-D herbicide by a polyphagous saturniid caterpillar.

A herbicide containing 2,4-dichlorophenoxyacetic acid (2,4-D) and related chemicals was fed to caterpillars of Eupackardia calleta, and the fate of the substances in the larvae and during further ontogenesis was followed by combined gas chromatography/mass spectrometry. The compounds were found in differing amounts in larval midgut, faeces, fat body/haemolymph, and even in an exocrine secretion produced by integumental glands. Furthermore, they were detected in samples from the resulting adult moths, indicating an intraindividual transfer. Since the individual development of E. calleta was distinctly accelerated by 2,4-D, possible impacts of the herbicide on the life history of the animals in the field are discussed. Based on the chemical data, hypothetical metabolic pathways for 2,4-D in E calleta larvae are proposed.

Influence of food and larval age on the defensive chemistry of Saturnia pyri.

Scolus secretions and hemolymph of caterpillars of Saturnia pyri fed with two different foodplants (Crataegis monogyna, Prunus spinosa) were chemically analyzed and their chemical similarities determined. The secondary-compound patterns obtained for the two body fluids showed no significant differences when compared between the two groups of alternatively fed last-instar larvae. Thus, the composition of these fluids of full-grown caterpillars is not influenced by the larval diet. However, younger larvae on P. spinosa revealed a diversity of compounds differing significantly from that of larger caterpillars fed with either C. monogyna (both body fluids) or P. spinosa (hemolymph only). This indicates that, on the one hand, the hemolymph composition is adapted to the changing physiological requirements of the given instars whereas, on the other hand, the defensive mixtures remain unaltered in the late larval instars due to a constant spectrum of potential enemies.

Comparative morphology and evolution of the funnel warts of larval Lymantriidae (Lepidoptera).

The larval funnel warts of 14 species of Lymantriidae (tussock moths) were investigated by means of scanning electron microscopy. The smaller, paired osmeteria on other abdominal segments were also inspected in four of the species. It seems that the bilaterally symmetrical funnel warts have developed by fusion of two smaller, single osmeteria. Based on the morphological findings from surface views and inside views of the structures, we made an attempt to reconstruct the pathway of evolution of the funnel warts. The high degree of specific modifications of the funnel warts appears valuable for analyses of the phylogenetic relationship of the investigated species.

Benzoquinones and hydroquinones in defensive secretions of tropical millipedes.

The defensive secretions of two tropical species of millipedes (the spirostreptid Telodeinopus aoutii and a species of Harpagophoridae) contain a complex mixture of closely related benzoquinones and hydroquinones. The major compounds are toluquinone and 2-methoxy-3-methylbenzoquinone, accompanied by the minor components, 2,3-dimethoxybenzoquinone and toluhydroquinone. Because of the large size and the geographic separation of the test animals a common defensive strategy of tropical, large millipedes against predation by vertebrates is assumed.

Attacus atlas caterpillars (Lep., Saturniidae) spray an irritant secretion from defensive glands.

The ability ofAttacus atlas caterpillars to spray a defensive secretion seems to be due to the fine structure of the integumental glands that produce it. The giant gland cells are fixed to stable cuticular rings surrounding the gland openings and tightly closed by cuticular lids. Probably by increasing hemolymph pressure, the lids are blasted off and the secretion spouts out. The fluid contains several aromatics, biogenic amines (e.g., acetylcholine, histamine), glycerol, and trehalose and exhibits tyrosinase activity. Deterrent effects of caterpillar secretion and hemolymph on predatory ants could be shown. Presumably the spraying process serves to apply the secretion to sensitive sites of vertebrate target organisms.