Hydropsyche vasoumittra, Schmid, 1961

Oláh, J. & Johanson, K. A., 2008, Generic review of Hydropsychinae, with description of Schmidopsyche, new genus, 3 new genus clusters, 8 new species groups, 4 new species clades, 12 new species clusters and 62 new species from the Oriental and Afrotropical regions (Trichoptera: Hydropsychidae), Zootaxa 1802, pp. 1-248 : 57-58

Hydropsyche vasoumittra species group

The Hydropsyche vasoumittra species group has been established by Malicky and Chantaramongkol (2000) with four species ( H. athamas , H. atlas , H. dhusaravarna and H. vasoumittra ) based upon the presence of numerous large sclerites in their phallic apparatus. This group having no phallotremal sclerits was used as outgroup in the cladistic analysis of H. hamifera species group ( Mey, 2003). The group is particularly species rich in the Oriental Region. A representative of this species group, H. dhusaravarna Schmid , was regarded one of the most primitive species in the genus Hydropsyche by the author. Malicky & Chantaramongkol (2000) placed species into this group based on the presence of a high number of large sclerites, spines or cornuti associated with, or embedded in, the enlarged membranous endotheca. Mey (1999b) noted that similarly to the species of the H. formosana species group, species of the H. vasoumittra species group all lack phallotremal sclerites. However, we consider that the sclerous structure at the end of endophallus is homolog with the phallotremal sclerite, present in more or less all species of the group. It is uncertain, however, whether the sclerous structure are remnants of the aedagus ( sensu Ross & Unzicker 1977 ). This was mentioned by Mey when stating that in primitive species of Hydropsyche , the endotheca with phallotrema is slightly eversible, probably by using retractor muscles attached to the lips of the phallotrema. Enlargement and sclerotization of the phallotremal lips may represent a development of the phallotremal sclerites. This morphological feature, with the less visible lips at the distal opening of the endophallus , is possibly a primitive state in the development of phallotremal sclerites. Mey (2003) recognized 2 derived characters for this species group: (1) presence of 5 or more pairs of endothecal spines, or cornuti, arranged in 2 rows along the dorsolateral surface of the endothecal terminalia; and (2) presence of paired, or unpaired, membranous process on the endotheca arising dorsally between the phallotrema and the tip of the phallic apparatus. Recognizing the possible primitive state of the phallotremal sclerites in the H. vasoumittra species group, we have found a third derived character consistently present in all its 4 species, especially visible in H. januha , new species: (3) appearance of phallotremal sclerites, or as Mey (2003) recognized, the presence of the chitinized internal lips. This derived character supports Mey’s explanation of the function of the small fold, or internal lips, at the distal opening of endophallus . These internal lips serve as attachments for the retractor muscle, and developed into a more sophisticated phallotremal sclerite for closing or opening the phallotrema in the process of interaction with the gonopore at the ejaculatory duct as indicated by Ross & Unzicker (1977).

The species group is disjunctively distributed along the southern Karakorum and Himalayas. The absence from Himachal Pradesh and West Nepal is probably due to sampling errors. The discovery of H. januha , new species in Meghalaya and Manipur expands the distribution of the species group further east and southeast.