*I2 OUR HOUSEHOLD INSECTS 



causing it to relax its hold. The flies, though so 

 particular in removing from their persons the slightest 

 trace of inanimate foreign matter, by sweeping and 

 scraping themselves with their legs, yet submit patiently 

 to the presence of their living burdens, even wjien they 

 get into places whence they could, one would imagine, 

 easily be removed. For example, a Musca domestica 

 that has just at the moment of writing alighted on the 

 window-pane, flew about unconcernedly with a large 

 mite clinging to its face in such a way as one might 

 suppose would have seriously interfered with the use 

 of both eyes and antennae. It did not seem, however, 

 in the slightest degree incommoded. Another external 

 parasite sometimes, but not so commonly, found, is an 

 animal belonging to a group closely allied to the mites, 

 viz., the book-scorpions or chelifers. It is a little 

 reddish creature with a pair of great pincers in front 

 like a scorpion, but differing in that the body does not 

 taper away into a tail, but ends abruptly. 



Amongst the internal parasites are various kinds of 

 small hymenopterous insects allied to the ichneumon 

 flies ; and an instance is recorded of an exceedingly fine 

 and hair-like nematoid worm, of the enormous length 

 of three inches, having been taken from the abdomen 

 of a house fly. M. Fourment, who records the fact, 

 states that, notwithstanding that the parasite had caused 

 a considerable enlargement of the body of its host, the 

 latter did not seem in any way inconvenienced in its 

 flight. 



We have now enumerated eight species of Musddce 

 which are more or less intimately associated with man, 

 and which, either by reason of some peculiarity % in 

 their economy, or simply in consequence of their nu- 

 merical abundance, often become a source of trouble and 



