The comparative morphology of epidermal glands in Pentatomoidea (Heteroptera)

A Comprehensive Survey of Stink Bug Pheromones - Extraction, Identification, Synthesis, Biosynthesis, and Phylogenetic Insights

Stink bugs (Hemiptera, Pentatomidae) are well known by the strong odor of the defensive compounds they release, which can mediate intra- and/or interspecific interactions. Pentatomidae is one of the largest families of Heteroptera and includes many phytophagous species that are considered pests of various crops, as well as predatory species that provide biological control. Against this background, numerous research papers in Chemical Ecology have focused on communication within this group. This paper reviews the chemical compounds reported for nearly ninety taxa, including sex and aggregation pheromones for fifty-three species of Pentatomidae. Based on these pheromones and proposed biosynthesis pathways, we hypothesize that sex/aggregation pheromones could play a role in taxonomic groups. Characters were determined and evaluated according to their distributions in recent taxonomic classifications, allowing for the inference of the phylogenetic positioning of three species never evaluated in previous taxonomic analyses.

External morphology of the abdominal glands in Asopinae (Hemiptera: Heteroptera: Pentatomidae)

Heteropterans communicate chemically through thoracic or abdominal glandular complexes. The dorso-abdominal scent glands (DAGs) are externalized by cuticular specialized structures forming the external scent efferent system (SES). Different groups in Heteroptera present other glands, such as the Asopinae (Pentatomidae), whose males can have ventral abdominal pheromonal glands externalized by cuticular modifications, called glandular patches (GPs). Here we describe the SES of DAGs and, for the first time, the GPs of 22 Asopinae genera. The ostioles of SES 1 vary in shape. SES 2 and SES 3 were restricted to scars, indicating that only the SES 1 remains functional in adults. The GPs are found mostly in segments V and VI. We have not found any difference in the morphological pattern between the SES of species bearing GPs and those lacking it, meaning that the acquisition of GPs is likely related to some sexual behavior, thus not as a complex structure replacing any role of the DAGs. The cuticle of the GPs is microsculptured, bearing many pores surrounding the base of sensilla being the pathway for the secretions to reach the outside of the exoskeleton. The sensilla may be adaptations to increase the contact surface, assisting rapid evaporation of the volatile secretions from the pores.

Chemical polymorphism in defense secretions during ontogenetic development of the millipede Niponia nodulosa

A mixture of defense compounds (benzaldehyde, benzoyl cyanide, benzoic acid, mandelonitrile, and mandelonitrile benzoate), found commonly in cyanogenic polydesmid millipedes, was identified in the non-cyanogenic millipede Niponia nodulosa. These compounds were major components in 1st-4th instars, but were absent in older instars and adults. Extracts of older instars and adults contained 1-octen-3-ol, 2-methyl-2-bornene, E-2-octen-1-ol, 2-methyl-isoborneol, and geosmin; these compounds were minor components in 1st-4th instars. This ontogenetic allomone shift may be explained by the high cost of biosynthesis of polydesmid compounds from L-phenylalanine being offset by their potency in protecting the insect during fragile and sensitive growth stages. However, as the cuticle hardens in older juveniles (5th, 6th, 7th instars) and adults, this allows for a switch in defense to using less effective and less costly volatile organic compounds (presumably microbial in origin) that are ubiquitous in the millipede's habitat or are produced by symbiotic microbes and may be readily available through food intake or aspiration.