(126) 



STRUCTURE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 367 



1. Chernes nodosus Schrank. 



There are frequently found attached to the legs of the 

 house-fly small scorpion or lobster-like creatures which are 

 Arachnids belonging to the order Pseudo-scorpionidea; 

 the term "chelifers" is also applied to them on account of the 

 large pair of cbelate appendages which they bear. The 

 species which is usually found attached to M. domestica is 

 Chernes nodosus Schrank (fig. 13). It is very widely 

 distributed, and my observations agree with those of Pickard- 

 Cambridge (1892), who has described the group. 



The species is 2'5 mm. in length and Pickard-Cambridges's 

 description of it is as follows : 



" Cephalothorax and palpi yellowish red-brown, the former 

 rather duller than the latter. Abdominal segments yellow- 

 brown; legs paler. The caput and first segment of the 

 thorax are of equal width (from back to front) ; the second 

 segment of the thorax is very narrow. The surface of 

 the cephalothorax and abdominal segments is very finely 

 shagreened, the latter granulose on the sides. The hairs on 

 this part as well as on the palpi and abdomen are simple, but 

 obtuse. The palpi are rather short and strong. The axillary 

 joint is considerably and somewhat subconically protuberant 

 above as well as protuberant near its base underneath. The 

 humeral joint at its widest part, behind, is considerably 

 less broad than long ; the cubital joint is very tumid on its 

 inner side ; the bulb of the pincers is distinctly longer, to the 

 base of the fixed claw, than its width behind ; and the claws 

 are slightly curved and equal to the bulb in length. " 



They appear to be commoner in some years than in others. 

 Godfrey (1909) says: "The ordinary habitat of Ch. nodosus, 

 as Mr. Wallis Kew has pointed out to me, appears to be among 

 refuse, that is, accumulations of decaying vegetation, manure- 

 heaps, frames and hot-beds in gardens. He refers to its occur- 

 rence in a manure-heap in the open air at Lille, and draws my 

 attention to its abundance in a melon-frame near Hastings in 

 1898, where it was found by Mr. W. R. Butterfield." In 



