252 DIPT ERA. 



the male they are in close contact, but are separated 

 in the female. The two ocelli cannot be seen from 

 above, but only in a front view of the head. The 

 antennae (Figs. 197, 199, af) are short, with the third 

 joint very much enlarged. They are often carried for- 

 ward, as seen in PI. XII., Figs. 196, 198. PL XII., 

 Fig. 199, represents the mouth parts, which are com- 

 plex in structure and fitted for piercing, sucking, and 

 lapping. The mandibles {md) and maxillae {inx\ 

 mx") are like sharp lances, and pierce the hide of 

 horses and cattle, sometimes causing their death. The 

 palpi of the first pair of maxillae (x') are large and 

 stout. The second pair of maxillae forms the tongue 

 or proboscis, and this pair is without palpi. The 

 operation of lapping food can be observed by chil- 

 dren if sweetened water is given a common house-fly. 

 In this insect the mandibles and first pair of maxillae 

 have become obsolete, but the proboscis is finely 

 adapted for lapping, having two broad, flat leaves 

 at its end. These are strengthened by bars which 

 roughen the inner surface so that a rasping organ is 

 produced (see p. 265). 



The legs (PI. XII., Fig. 197, /', /", /'") are very 

 long, and the feet have five joints, two claws, and a 

 fleshy two-lobed cushion furnished with hairs which 

 excrete an adhesive liquid, enabling the insect to walk 

 on a ceiling with safety. Home ^ gives magnified 

 figures of the last joint of the toe of a blue-botde fly 

 as seen when the insect is walking in such a position. 



1 See Lectures on Comparative Anatomy, Vol. IV., Pis. 

 LXXXI.-LXXXVI. 



