362 EXTERNAL ANATOMY OF INSECTS. 
of Aphaniptera (Pulex L.), in which the ordinary 
Trophi are replaced by a bivalve beak, between the 
valves of which there appear to be three lancets *. 
It includes the Lamina, Scalpella, and Ligula. 
A. Lamina (the Lamina). Two corneous plates which 
are laterally affixed to the mouth of a flea, pro- 
bably representing the Mandibule of the perfect 
mouth, which somewhat resemble the beak of a 
bird ©. 
B. ScaLpPe.ia (the Lancets). ‘The two upper or outer 
instruments, probably for making an incision in the 
skin; these are flat and acute, and seem to repre- 
sent the Mazille of the perfect mouth*. 
C. Ligura (the Ligula). A capillary instrument between 
the lancets; probably representing the tongue of 
the perfect mouth ¢. 
6. Rostetium (the Rostellum). The oral instruments 
of Pediculus and some other Aptera, in which the 
ordinary Trophi are replaced by an exarticulate re- 
tractile tube, which exerts a retractile siphuncle. 
It includes the Tubulus and Szphunculus. 
A. Tusutus (the Tubulet). The tube or retractile base 
of the Rostellum. 
B. SrpnHuncuuus (the Siphuncle). The real instrument 
of suction, which when unemployed is retracted 
within the tubulet. 
Besides the above variations from the type of what I 
call a Perfect Mouth, there are others in which the parts 
of the Trunk appear to aid in the conversion of the food, 
4 Prate VII. Fie. 8. » Tbid. ec’. 
© Thid. d’. Maxillary Palpi h”. ¢ Thidse’. 
