368 
C. GOKDUN HEWITT. 
view of tliese facts it is not ditiicult 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 
pupae in those places and in crawling about, during the pro- 
cess of di’ying their wings, etc., their legs were seized by the 
C. nodosus. 
The inter-relation of the Chernes 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 Chernes, 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 he rues, 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 chela). It is suggested by some that 
the Chernes seizes the legs of the fly without I’ealising the 
size of the latter. Notwithstanding its size, however, they 
remain attached until the fly dies and then feed upon the 
