Date of Award

8-1977

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

David A. Etnier

Committee Members

Dewey L. Bunting, Melborne Whiteside, Susan Riechert, Paul Parmalee

Abstract

Larvae of caddisfly genus Hydropsyche are among the most encountered and abundant organisms in lotic environments in eastern North America. Yet, little is known of the larval stages of this genus. Previously, the larvae of only 12 species were known. In addition to these 12, descriptions of the larvae of additional 27 species are presented here for the first time.

Larval-adult associations were made by simutaneously collecting mature pupae (metamorphotypes) and larvae. Species determination is based on the cleared male genitalia of the mature pupae. The abdomen was cleared in strong KOH so that sclerotized structures lying beneath surrounding tissues could be examined. Larvae were studied under both compound and dissecting microscopes. The scale hairs, club hairs, and minute spines of the abdomen are best studied under high magnification. The larval abdomen was cleared in strong KOH and put into glycerin on a microscope slide for examination.

Presented here are descriptions of the larvae of 18 of the 24 eastern North American species of the scalaris group; 14 of the 15 nominal eastern species of the bifida group; 5 of the 9 species of the depravata group; and the single species of the cuanis group, H. cuanis Ross. A key is provided for these known larvae, and incorporated into the key are a number of characters previously unknown in the taxonomy of Hydropsyche larvae. The key is based on the last or next to the last instar larvae since color patterns may vary greatly in earlier stages.

The larvae of the two species, H. piatrix and H. decalda, have not definitely been associated with metamorphotypes; however, larvae were collected near or at the type locality for each species. The presumed larva of these two species is described, illustrated, and keyed. The larvae of two undescribed species are also described, illustrated, and keyed, respectively as species 1 and species 2. Also included is a listing of all unassociated species with their known distribution and literature citations.

The characters utilized in the key to facilitate separation of the various species include the following: color pattern of the head; the morphology of the anterior margin of the frontoclypeus; the presence or absence of spines and/or bristle-like setae on the frontoclypeus; the presence of a large tubercle on the center of the submentum; the presence or absence of club hairs, scale hairs and/or minute spines on the dorsum of the abdomen; and the presence of large, heavily sclerotized spines on the venter of the anal legs. The minute spines on the abdomen are described and utilized as a taxonomic character for the first time in this key.

In addition to the description of the larva, the following are presented for each of the associated species of Hydropsyche: known range, notes on biology, diagnosis, intraspecific variation, material examined, complete literature survey and synonomies, and an illustration of the head capsule and pronotum.

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