Comparative investigations of the distal part of the vesica spermalis (‘glans’) of the anisopteran male secondary copulatory apparatus reveal three different ‘solutions’ of combining the emptying-mechanism of the sperm-reservoir with a ‘washing out’ of sperm of the male predecessor. The responsible apparatus of the glans—actually driven by pressure-changes inside the erectile organ, which is a…
In the premontane rain forests of northwest Costa Rica, patches of secondary forest can contain high densities of large Vriesea spp. bromeliads. Such patches contain an average of 6,470 ± 1,080 (s.e.) larvae ha-1 of the bromeliad-dwelling pseudostigmatid, Mecistogaster modesta, ca 3 6× higher than larval densities that we previously reported for adjacent primary forest.
The larva of Mecistogaster linearis is described and illustrated from specimens collected within or near the Río Dantas Wildlife Refuge at the north-western border of the Barbilla National Park on the Costa Rican Caribbean slope. Characters of F-0 larvae permit easy separation from Megaloprepus caerulatus, a species coexisting with M. linearis. Diagnostic characters include overall…
In odonates, female specific color polymorphisms appear to be an evolutionary response to sexual harassment, but we know little about the decision rules males use when searching for variable females. For two sympatric species of Enallagma, we measured male responses to live female variants under field conditions, early and later in the day. In the…
Progomphus obscurus is one of the most abundant dragonflies in South Carolina, USA. We collected dragonfly larvae from 127 sites in the Enoree River and nine of its tributaries, and correlated the abundance of P. obscurus larvae with physical and chemical characteristics of these streams. As expected for this burrowing species, larval abundance varied among…
Communities have a nested-subset structure if the species found in species-poor assemblages are also found in progressively more species-rich assemblages. This nested-subset structure can be caused by differential colonization rates among species, differential extinction rates among species, or nested niche space. In this study, the assemblages of larval odonates in the Enoree River of South…
The microdistribution patterns of larval Gomphus graslinii and Oxygastra curtisii in three rivers in southern France were studied. While G. graslinii was caught mainly in sandy reaches covered with leaf litter, O. curtisii was found almost exclusively clinging to alder roots at the river margins. Preferences of habitat structure were determined from habitat selection experiments…