472 EXTERNAL ANATOMY OF INSECTS. 



have overlooked this last piece, since they reckon only 

 six pieces in the flea's mouth a : but the hand and eye of 

 our friend Curtis have detected a seventh, as you see in 

 his figure. From this account it appears, that the elon- 

 gation of the organs of the Aphaniptera Order is at the 

 expense of the labium and its palpi. 



v. Rostellum. — So little is known of the composition 

 of the next kind of imperfect mouth, that I need not en- 

 large upon it. It is peculiar to the louse tribe [Pedicu- 

 lidce\ and it consists of the tubulet ( Tubulus), and si- 

 phuncle (Siphuncidus). The former is slenderer in the 

 middle than at the base and apex, the latter being tur- 

 gid, rather spherical, and armed with claws which pro- 

 bably lay hold of the skin while the animal is engaged in 

 suction. When not used, the whole machine is with- 

 drawn within the head ; the siphuncle, which is the suc- 

 torious part, being first retracted within the tubulet, in 

 the same way as a snail retracts its tentacula b . This ap- 

 paratus seems formed at the expense of all the other 

 organs. 



There are some other kinds of imperfect mouth, 

 which, though they seem not to merit each a distinct 

 denomination, should not be passed altogether without 

 notice. The first I shall mention is that of the family of 

 Pupipara Latr. (Hippobosca L.). It consists of a pair 

 of hairy coriaceous valves, which include a very slender 

 rigid tube or siphuncle, the instrument of suction, which 

 Latreille describes as formed by the union of two seti- 



3 Rosel. ii. t. iii./. 15. Latreille Gen. Crust, et Ins. iv. 365, 

 b Swammenlam Bibl. Nat. t. ii. f. 4. 



