Corydalus

Abstract: Phylogenetic relationships of the World genera of dobsonflies, subfamily Corydalinae, are reappraised, as well as those of species of the New World genus Corydalus, both on the basis of morphological characters. Previous phylogenetic hypotheses of dobsonfly genera by Glorioso, Penny, and Contreras-Ramos, respectively, are re-evaluated, and a fourth revised phylogeny is presented. Ninety-five characters of 10 taxa, one outgroup and nine ingroup taxa, were used in the updated analysis of Corydalinae. It recognizes four lineages, with Chloroniella as sister to the other three, of which the Nevromus lineage (Acanthacorydalis + Nevromus + Neoneuromus) is sister to the Corydalus lineage (Chloronia + Platyneuromus + Corydalus), and both as a group are sister to the Protohermes lineage (Protohermes + Neurhermes). The main changes in the updated Corydalinae phylogeny are the placement of Chloroniella as sister to all other dobsonfly genera, and the placement of Acanthacorydalis as a member of the Nevromus lineage. Previously, Penny had proposed Chloroniella as sister to all dobsonfly genera except the Protohermes lineage, and both Glorioso and Penny, respectively, placed Acanthacorydalis as sister to the Corydalus lineage. About Corydalus, its species phylogeny is herein updated, as four species from Venezuela were added to the genus after its taxonomic revision. For the new phylogeny, 120 characters of 35 taxa, two outgroup and 33 ingroup taxa, were used. It produced a strict consensus of two trees, better resolved than the previous one. The C. arpi species group is moved to sister of all other species except the C. cephalotes species pair, while the C. batesii species group is conserved, being the only unresolved group within the phylogeny. Two of the species added, C. hayashii and C. mayri, belong to the well defined C. arpi species group, of Guayana Shield affinity, whereas C. crossi is sister to a large and widespread group beginning with the C. nubilus species group, and C. clavijoi is sister to C. tesselatus within the latter group.

Abstract: Phoretic associations among three species of Chironomidae (Thienemanniella sp. nov., Rheotanytarsus sp. 1, and R. sp. 2) and two genera of Corydalidae (Corydalus sp. and Chloronia sp.) were studied in 13 streams in northwestern Costa Rica that varied in size, elevation, and water chemistry. Thienemanniella sp. nov. seemed to be obligatorily phoretic on Corydalidae larvae, while Rheotanytarsus sp. 1 and R. sp. 2 were also found on other benthic substrates. The number and location of chironomids on megalopteran larvae were assessed over a 9-mo period (February to October). Corydalus sp. was the preferred host for all three chironomid species. Site selection by Chironomidae was related to age of the chironomid (e.g., late instar Thienemanniella were on the thorax while earlier instars were on the abdominal gills). Large megalopteran larvae supported more chironomids than smaller larvae.

Abstract: The adult male, adult female, pupa, and larva of a new genus (Tempisquitoneura) of midge (Diptera:Chironomidae) are described and illustrated from specimens collected and reared from Corydalus (Megaloptera:Corydalidae) in northwestern Costa Rica. Larvae and pupae of the midge live attached to the Corydalus larvae. The genus belongs in the Corynoneura group of the subfamily Orthocladiinae, but its relationship to the two other described genera in the group (Corynoneura and Thienemanniella) will remain unclear until more Neotropical members of this group are described and analyzed in all life stages.

Abstract: Male–male competition is strongly affected by female presence. In insects with primitive features such as megalopterans, however, it is not known how aggressiveness is expressed in the context of female presence. Here we examined the effect of social environments on the use of secondary sexual traits in the sexual behavior of the Mexican dobsonfly Corydalus bidenticulatus (Megaloptera: Corydalidae). Males of this species have exaggerated traits such as disproportionally elongated mandibles with no dentition, which is a secondary sexual trait used in competition over female access as well as males of other Corydalus species. We investigated how male–male interactions are carried out, and the scaling relationships of sexual and non-sexual traits. Our results show that males of C. bidenticulatus are not indiscriminately aggressive. The decision whether to fight or not is affected by their social environments: males are aggressive against other males only when the presence of a female is detected. Results also suggest that mandibles and antennae are sexually dimorphic, being exaggerated and showing positive allometry only in males. In contrast, male genitalia, a sex-specific trait, show negative allometry.