THE LARVAL AND PUPAL STAGES OF THE BIBIONIDAE. 229 



The most striking difference is exhibited in the cuticle. In both species the 

 cuticle of the full-grown larva bears a great number of small, irregularly-shaped, 

 scale-hke structures. In B. marci the largest of these scales bear one stout spine, 

 while in B. lacteipennis (fig. 14) the scales are much less well developed, and only 

 those on the processes, and on the anterior part of the ventral side of the first segment 

 of the body, bear these spines. The latter are, moreover, less stout than those of 

 B. marci, and there do not seem to be more than two on any scale. On the ventral 

 surface of the twelfth segment a few of the scales bear single, long, stout spines. 



Fig. 14. Portion of cuticle of larva of Bibio 



lacteipennis from dorsal surface of fourth segment : 



a, lateral view ; h, vertical view ; X 330. 



The only apparent difference in the mouth-parts is the presence of a slight median 

 projection between the two processes at the anterior end of the submentum. 



The larva bears a pair of protrusible pseudopod-hke structures at the end of the 

 twelfth segment, which are relatively larger and better developed than is the case 

 in B. marci. 



The alimentary canal, Malpighian tubes and caeca appear to be similar to those 

 of B. marci, and there is no posterior caecum. 



The length of the full-grown larva is about 15 mm. 



Pupa. 



The pupa of Bihio lacteipennis bears a considerable resemblance to that of 

 B. marci. It is distinguished from the latter by its smaller size and the somewhat 

 greater development of the median process at the anterior end. The male pupa 

 bears a pair of small, blunt processes, slightly ventral to the median process and 

 situated on the anterior portion of the eyes. Length of pupa 7 to 7-5 mm. 



Bibio venosus, Mg. 



Larva. 



A few larvae of this species were found in leaf-mould at Brockenhurst on 22nd 

 March 1920, but unfortunately before they could be thoroughly examined they 

 had all pupated. 



The mouth-parts do not show any noticeable difference from those of Bihio 

 marci, and the number and arrangement of the spiracles and processes is similar. 

 With this larva again, as in the case of B. lacteipennis, the chief difference from 

 B. marci is in the scales on the cuticle. As in B. lacteipennis, these scales are very 

 slightly developed and do not bear spines, except those on the twelfth segment 



