84 [-'^n-ii, 



ON THE PREPAEATORY STATES OF DIPLECTRONA FELIX, 



McLACH. 



BY KENNETH J. MORTON, P.E S. 



This very lively and interesting little caddis-fly occurs sparingly 

 in one of our warmer glens. I had long held the idea that a Hydro- 

 psyclie-\We larva, which lives in springs and trickling streams along 

 with such larvae as those of Cruncecia irrorata, JBercsa, &e., was that 

 of Diplectrona, but not until last summer was this proved by the 

 rearing of the imago. As the preparatory states have not hitherto 

 been noticed, it may be worth while putting on record a few notes 

 about them, especially as they seem to throw some light on the 

 alliances of the genus. 



The head of the larva is a very short-oval, almost as broad as long, depressed, 

 thickly beset with short spinous hairs, with a few longer hairs in front ; clypeus 

 large ; under piece very small. Labrura narrowly transverse, heavily fringed at the 

 sides. Mandibles strong, deeply dentate, with a number of hairs on the back. 

 Maxilla; armed with spines, ciliated inwardly ; palpi 4-]'ointed, tapering. Colour of 

 head brown ; eyes in a yellowish space. 



The thoracic segments are all more or less chitinous, quadrate, not differing 

 greatly in size, prothorax smallest, angles moderately sharply defined, hind angles 

 slightly rounded. The legs are strong, femora of fore-legs dilated ; the second and 

 third pairs each of slightly greater length than the pair preceding. Prothorax and 

 mesothorax brown, bordered with black; metathorax paler, with black margins. 



The segments of the abdomen increase gradually in size to about the 4th, then 

 fall away equally gradually to the 8th ; the 9th segment is small. The retractile 

 anal filaments are five in number. The anal limbs are long, with a pencil of hairs 

 on the inner side of the apex, and a strong, simple claw placed inferiorly. Tracheal 

 branchiae in large branched fascicles occur on the meso- and metasterna, and on the 

 sterna of the first six abdominal segments ; mesothorax apparently with two fascicles 

 only, the other segments each with four arranged in two series, the outer (posterior) 

 row the larger, each fascicle arising from two semi-independent bases. In addition, 

 segments three to seven of abdomen have each on tlie lateral region two or three 

 branchia-like processes. 



The materials for the nymph state are unfortunately very limited, only the 

 cast-off slough of the single bred example of the insect. This skin, however, shows 

 very well that the characters of Hydropsyche which the larva has, are likewise a 

 feature in the later state. The mandibles are broad at the base, elongate, with four 

 and five apical teeth respectively, thus much as in Hydropsyche ; and the posterior 

 abdominal appendages are also similar to what prevails in that genus. The large 

 branchia-like lateral appendages of the abdomen are also common to both genera. 

 True fasciculated tracheal branchiae exist, but their distribution and form are a little 

 uncertain from the material in hand. Nor can the formula of the dorsal hooks be 

 safely given from the single nymph-skin. 



The economy and habitations of the larva seem to be of the type prevailing in 

 Hydropsyche. 



