(127) 



368 C. GORDON HEWITT. 



view of these facts it is not difficult to understand its frequent 

 occurrence on the legs of flies, which may have been on the 

 rubbish heaps either for the purpose of laying eggs, or, what 

 is more likely, because they have recently emerged from 

 pupas in those places and in crawling about, during the pro- 

 cess of drying their wings, etc., their legs were seized by the 

 C. nodosus. 



The inter-relation of the Ch ernes and M. domestica, 

 however, is one of no little complexity; much has been 

 written and many diverse views are held concerning it. An 

 interesting historical account of the occurrences of these 

 Arachnids on various insects has been given by Kew (1901). 

 Three views are held in explanation of the association and 

 they are briefly these : First, that the Ch ernes, by clinging 

 passively to the fly, uses it as a means of transmission and 

 distribution; second, that the Arachnid is predaceous ; and 

 third, that it is parasitic on the fly. Owing to the unfortunate 

 absence of convincing experimental proof in favour of either 

 of the last two opinions, it is practically impossible to give 

 any definite opinion as to the validity of these views ; never- 

 theless they are worthy of examination. 



The dispersal theory was held by Pickard- Cambridge and 

 Moniez (1894). Whether the other views are held or not 

 there is no doubt that such an association, even if it were 

 only accidental, would result in a wider distribution of the 

 species of C h ernes, as the flies are constantly visiting fresh 

 places suitable as a habitat for the same. Except in one or 

 two recorded cases the Arachnids are always attached to the 

 legs of the fly, the chitin of which is hard and could not be 

 pierced, a fact which is held in support of this theory as the 

 only explanation of the association. 



The parasitic and predaceous views are closely related. 

 The Pseudo-scorpionidea feed upon small insects, which 

 they seize with their chela3. It is suggested by some that 

 the Chernes seizes the legs of the fly without realising the 

 size of the latter. Notwithstanding its size, however, they 

 remain attached until the fly dies and then feed upon the 



