HYDROPTILIDAE (TRICHOPTERA) 

 OF AMERICA NORTH OF MEXICO 



by 



R. L. Blickle^ 



HYDROPTILIDAE 



These small Trichoptera, usually less than 6 mm in length, 

 are known as microcaddis flies. The larvae are aquatic but do not 

 construct cases until the last instar, being "free living" in their 

 earlier stages. In the imago the antennae are generally stout and 

 shorter than the body length. Ocelli may be present or absent, 

 most genera have ocelli. Maxillary palpi five segmented in both 

 sexes. Legs moderately long, hairy; spurs may be present on the 

 tibiae either apically, preapically or both. The spurs are usually 

 larger than spines, are movable and may be covered with sharp 

 points. The spur formula, as in the genus Hydroptila for example, 

 would be 0-2-A. This indicates the number of spurs on the fore, 

 middle, and hind legs respectively. Since there are never more 

 than two spurs together and the apical ones are indicated first, 

 thus in the genus Hydroptila there would be on the foreleg, 2 

 apical ones on the mesotibia and 2 apical plus 2 preapical spurs on 

 the metatibia. Both sexes have the same spur count. Wings 

 generally acute at apex with reduced venation, although the vena- 

 tion may be difficult to see due to the numerous hairs on the 

 wings. Hair fringes of the wing may be several times the width of 

 the wing itself, especially the hind wings. 



The spur formula and the presence or absence of ocelli enables 

 one to separate some genera from others using only these criteria. 

 The following table gives the spur formula and the presence or ab- 

 sence of ocelli for each genera. As can be noted the genus Neotri- 

 chia may be immediately separated by the spur formula. In the 

 group with 0-2-4 spurs the Hydroptila are separated by lack of 

 ocelli. In the next group of 0-3-4 spurs the Orthotrichia also are 

 separated by lack of ocelli. In the next group of 1-3-4 the genus 

 Dibusa is the only one without ocelli. Thus by observation of the 

 spurs and ocelli, one fourth of the genera may be determined. 



The small size of the Neotrichia and the possession of "scent 

 caps" on the dorsal part of the head of male Hydroptila also give 

 clues that are helpful in determination of species of these genera. 



Taxonomic determination to species is based on the male geni- 

 talia primarily. There is a general resemblance among those spe- 

 cies in each genus and one can recognize the proper genus quite 

 readily with experience. The female specimens in most instances 

 will have to be run through a genera key to place them properly, 

 although here again with practice they may be easily recognized as 

 to the correct genus. 



— Professor of Entomology, Department of Entomology, Univer- 

 sity of New Hampshire. 



