Population Ecology of Two Species of Pasimachus (Coleoptera: Carabidae) in the Sandhill Habitat of Florida

Abstract

The population ecology of Pasimachus subsulcatus Say and of P. strenuus LeConte was studied with beetles captured by pitfall trapping. We searched for patterns in: (1) activity/density, (2) reproduction, (3) body size, and (4) parasitization. Females and males of both species were most active/dense in spring and autumn; females of both species were especially active/dense, relative to males, in late summer-early autumn; few females of both species bore post-vitellogenic eggs in summer; and males of P. subsulcatus produced mature sperm in spring and autumn. It was concluded that mating occurs in spring and autumn for both species, and oviposition in summer-early autumn. Our data suggest that relatively high percentages of both female and male P. subsulcatus trapped in late summer-early autumn were relatively large. In most months, females of P. subsulcatus were, on average, larger than males, but the two sexes of P. strenuus were similar in size. About 1.4% of P. subsulcatus and 3.3% of P. strenuus were parasitized by tachinid flies. Parasitization of both species peaked in late summer-autumn, and there was no evidence that paratization was influenced by sex, size, or female gravidity, with one exception. Small individuals of P. subsulcatus were parasitized more often than one would expect from their representation among captured individuals.