Belonuchus, Nordmann, 1837

Frank, J. H. & Barrera, R., 2010, Natural history of Belonuchus Nordmann spp. and allies (Coleoptera: Staphylinidae) in Heliconia L. (Zingiberales: Heliconiaceae) flower bracts, Insecta Mundi 2010 (110), pp. 1-12 : 10

On Belonuchus and other Staphylinidae associated with Heliconia bracts

An unresolved question about B. cephalotes is why the adults rotate the abdomen. Could this be to disperse a pheromone? Another question is why the color pattern of those adults (black, with the apical abdominal segments yellow) matches the color pattern of B. agilis and of Philonthus nr. infimus . Is it pure coincidence that the yellow color is shared also by the flowers of the Heliconia spp. that some of them inhabit?

Seifert and Seifert (1976a) supposed that mosquito larvae formed a major part of the diet of Odontolinus fasciatus adults in Costa Rican Heliconia bracts. Although newly hatched larvae of 11 Quichuana and Beebeomyia were eaten, they were thought generally to be unavailable to this predator because of their restriction to partially opened bracts which O. fasciatus could not enter. Those investigators made no mention of possible predation by O. fasciatus on larger Quichuana and Beebeomyia larvae, which necessarily occur in older, open bracts, and we do not think that possibility should be dismissed. However, we agree that prey availability in the habitat is the most likely determinant of diet for both Odontolinus and Belonuchus .

These conclusions are supported by the records of occurrence of these and other Belonuchus in other decaying vegetable materials such as cacao husks, bananas, breadfruit, and fallen and rotting citrus fruits. Dipterous larvae usually are abundant in such habitats. It is possible that the natural habitat of at least some of these species is Heliconia bracts, but that human cultivation of these crops in the Neotropics expands the habitat available to them, if only at those seasons when rotting husks or fruit harbor concentrations of prey larvae. This association between these Belonuchus (and a few close allies) is not pure happenstance because the corollary of the observation is consequential: the family Staphylinidae includes thousands of genera, many of them with individuals of large size, but large individuals of other genera were NOT collected in the Heliconia bracts sampled. To the extent that other staphylinids were encountered in the Heliconia bracts sampled, they were Coproporus (Tachyporinae) and occasionally Medon (Paederinae) with much smaller individuals and (undoubtedly) other diets. The hypothesis presented here is that quite a few species of Belonuchus (and a few close allies) have evolved an association with Heliconia bracts, and this association is most prominent in those species whose adults can immerse totally in water ( B. cephalotes and O. fasciatus ) to attack mosquito larvae and pupae. By such attacks they may structure the prey community. Future studies may be used to test this hypothesis.

The stage seems to be set for many more ecological studies to document the fascinating behavior and effects of these and many more Belonuchus spp. associated with Heliconia spp. Thanks to Berry and Kress (1991) the Heliconia spp. can now be identified even by entomologists. Unfortunately, there is no revision of the Neotropical Belonuchus species. The senior author (JHF) was able to identify those he encountered only because he believes in the maxim that every insect ecologist should become proficient in identification of at least one taxon of insects, and he selected Staphylinidae (an extremely large family) for attention. The species occurring in the West Indies were documented as 14 by Blackwelder (1943); those of the USA were documented as nine ( Smetana 1995) but then B. agilis was detected in Florida ( Frank 2004) raising the total to 10; many dozens have been reported from the Neotropics. So now we see that the preliminary task is for an insect taxonomist to revise the Neotropical species of Belonuchus .