1884. 



125 



rOTES ON THE LARVA,. &c., OF ASYNARCEUS CCENOSUS, CURT. 

 BT KENNETH J. MORTON. 



Asynarclius coenosios, the only British representative of a genus of 

 Vrichoptera which is boreal in its distribution, is a very common insect 

 uring the months of August and September on the elevated moors of 

 his district, and no doubt occurs in similar localities all over Scotland 

 ,nd the northern part of England. This season I succeeded in rearing 

 he species, and am thus enabled to give a few notes concerning the 

 ijirva, nymph, and case. 



'' The larvae were abundant during the summer in the pools of a 



eat bog (about 800 ft. above sea-level), and, as far as I could dis- 



Dver, were the only caddis-worms which occurred there. Out of a 



;w taken home at the beginning of August and placed in a glass 



el with a piece of peaty earth, one in a few days fixed its case to 



;c peat and became quiescent. On the evening of the 31st of the 



me month, a nymph was observed swimming about in a vigorous 



anner. It very soon left the water and ascended to the muslin 



<'vering of the glass. The perfect insect, a $ , appeared after a short 



iterval. 



tm j! The larva appears to be of the usual Limnophiliform type, with a 



\ ^11 ovate head, almost quadrate prothorax and transverse meso- 



;-K torax ; the abdominal segments slightly depressed, and from the third 



:f f the penultimate inclusive with a lateral thick fringe of very short, 



L^e hairs. The head and pronotum are blackish-fuscous in colour ; 



1 sonotum paler fuscous, with dark dots and streaks, and narrowly 



1 rgined with blackish posteriorly; rest of body greenish-yellow; 



r [)iratory filaments whitish. 



A nymph taken from its case, and probably not quite mature, was 



i^iformly pale yellowish, excepting the eyes, which were blackish. 



T e mandibles agree in form with the figure of those of Limnophilus 



n the "Trichoptera Britannica." The respiratory filaments rather 



fiuierous, arranged on either side of the lateral lines; the last three 



a lominal segments have a strong lateral fringe ; anal extremity with 



t J long, slender processes (present also in StenopJiylax and Halesus^ 



al probably common to all nymphs belonging to the Limnophilida) . 



r ' tarsi of intermediate legs fringed with fine, rather long, hairs : 



e legs, I take it, are the principal natatory organs in the nymph. 



When the larva is young, the case is rather loose, long, slender, 



^Ihtly curved, composed of imbricated short lengths of fine stems. 



•^ ' older case is firmer, made of what appear to be small pieces of 



