Short review of the presocial evolution in Coleoptera

Abstract

A brief synthesis of presocial evolution in the insect order Coleoptera is presented. Most beetles are solitary, but in many species and/or higher taxa conglobations, aggregations and a wide variety of parental care types is known. The nonparental forms of inter-individual association are mostly pheromone controlled aggregations without phenotype changes. Within the range of parent-offspring relationships the most interesting sociogenetic events have been observed, and in at least seven-eight families (or “subfamilies”) a true subsocial level is attained.

The parental (subsocial) evolutionary pathway often starts from a more selective egg-laying mode, “care for eggs”, that probably evolved towards “nesting”, i.e. the building of paedotrophic nests if food relocation is performed, or towards “nutritional sheltering”, if a shelter for the eggs is dug in the larval feeding substrate. A post-natal relation to the offspring is achieved when the mother (the parents) remain in the nest or near the eggs. As in the Heteroptera, a more passive kind of brood care (“brood watching”) has to be separated from the more active “nursing of the offspring”, where direct feeding (trophallaxis), acoustic communication and transmission of microorganisms make the parent/offspring relationship more close. The nursing level seems derived from nesting or from nutritional sheltering, no evidence is found of a further evolution of brood watching.

Up till now, only in a single family, the Passalidae, has a higher level of sub-sociality been ascertained, with generation overlapping and cooperative nursing of the older larvae and pupae.

KEY WORDS:

• sociogenesis
• presocial evolution
• brood care
• Coleoptera
• behaviour