112 The Irish Naturalist. November, 



Abdomen with feebly developed terga, the cuticle covered 

 with numerous minute tubercles giving a roughened appear- 

 ance to the body (fig. 1, i) ; last abdominal tergum with 

 short median spine (fig. I, 8). 



Cerci prominent, sub-conical, inserted close together, 

 each with a short dorsal spine and terminal, elongate, 

 flexible bristle (fig. I, 8). 



Length of full-fed larva 4 mm. 



Colour mxottled brown. 



Comparison of Larva of Megasternum with allied 



Genera. 



The general appearance of the Megasternum larva is 

 very like that of the larval Cercyon described and figured by 

 Schiodte. According to him the larva of Cercyon is legless, 

 while, as stated above, the Megasternum larva has clearly 

 recognisable though vestigial legs. It is, therefore, as 

 regards this character, intermediate between Cercyon and 

 Sphaeridium, whose grub according to Schiodte ^ has 

 small but distinctly segmented legs. The head in the 

 Megasternum larva is relatively broader than in Cercyon ; 

 the segments and terminal spine of the feeler are shorter, 

 the large antennal papilla relatively shorter and stouter. 

 In both genera, the larvae agree in the curious and character- 

 istic asymmetry of the mandibles, the only notable difference 

 being the feebler development in Cercyon of the serrations 

 on the inner edge of the left mandible as compared with 

 the Megasternum grub. 



The base of the hypostome, rounded in the latter, is 

 triangular in Cercyon, and the labial palps of Megasternum 

 are shorter and thicker. In the Megasternum larva the 

 mesonotum and metanotum are more strongly developed 

 than in Cercyon. The cerci in the latter bear elongate 

 lateral bristles in addition to the terminal ones present in 

 Megasternum, the stout dorsal spines of which appear to 

 be absent in Cercyon. 



Cambridge. 



1 Op. cit., pp. 220-1, pi. vi. figs. 6, 13. 



