Dispersal of Phraortes illepidus (Phasmida: Phasmatidae) Eggs by Workers of the Queenless Ant, Pristomyrmex punctatus (Hymenoptera: Formicidae)

Eggs of some stick insects bear external appendages called capitula. Foraging worker ants attracted by capitula disperse eggs in a response similar to the responses of workers to elaiosome-bearing seeds of many plants. For this study, we conducted rearing experiments in the laboratory to elucidate the interspecific relation between the queenless ant, Pristomyrmex punctatus Smith, and the stick insect, Phraortes illepidus (Brunner von Wattenwyl) of which eggs bear capitula. Eggs of P. illepidus were proposed to P. punctatus in the laboratory. Capitula were removed from most of the eggs not only when ants were starved but also when ants were well-fed. In large rearing containers, eggs were transported by ants from their place of origin. Many eggs were transferred horizontally on the surface. Although some eggs were found in the artificial ant nests, it is likely that stick insects are not in active ant nests at the time of hatching in nature because of P. punctatus nest-moving habits. The percentage of eggs buried in the sand was small. Furthermore, most of the buried eggs were found at less than 3 cm depth. Results show that many P. illepidus hatchlings can reach host plants safely without being attacked by ant workers. These results suggest that P. punctatus can be a good partner of P. illepidus. Ants disperse eggs of slow-moving stink insects in exchange for some nutrition from capitula.

Sasakia Charonda (Apaturinae: Nymphalidae) and its Three Related Butterfly Larvae Use Halitosis to Repel Predators

Accidentally, we discovered that Sasakia charonda (Nymphalidae: Apaturinae) larvae disturbed by ants or humans released volatile compounds from their mouth; thus, we tried to identify these halitosis. We collected halitosis directly from the mouths of S. charonda larvae into volatile-collecting tubes. Trapped halitosis were subjected to gas chromatography-mass spectrometry (GC–MS). We confirmed the identity of eleven substances by comparison to GC of known standards, and inferred them to be mainly alcohols and aldehydes/ketones, with main chains of 4–5 carbons. Three of the chemicals in these halitosis, 2-butanol, 1-penten-3-ol and 3-pentanone, affected the behavior of Pristomyrmex punctatus and Formica japonica ants that co-inhabited the S. charonda rearing cage. We concluded that the substances we identified in this study were used as defensive halitosis, analogous to osmeterium emissions specific to Papilionidae butterflies. Based on smell, Holikawa found that Hestina assimilis and H. persimilis larvae have closely related halitosis. Thus, we also analyzed the halitosis of these two species as well as Apatura metis, another Apaturinae, using the same methods. We found that these species also release halitosis. The composition of the substances of H. assimilis and H. persimilis were somewhat similar to that of S. charonda, whereas that of A. metis differed. Some of the substances also induced defensive behavior in these species of Apaturinae larvae.