470 EXTERNAL ANATOMY OF INSECTS. 
tube, which seemed to be a trachea». 'To animals that — 
are without lungs, and breathe by ¢rachee, suction must 
be performed in a very different way from what it is by 
those that breathe by the mouth : and as in the very ex- 
tended organs in question the fluid has a long space to 
pass before it reaches the pharynx, in some way or other 
these lateral tubes may have the power of producing a 
vacuum in the middle tube, and so facilitate its passage 
thither. Wesee, in the anélia, that the maxillz receive 
their vast elongation at the expense of all the other or- 
gans, except the ladzal palpi. 
iv. Rostrulum>*.—An animal very annoying to us af- 
fords the type of the next kind of imperfect mouth—I 
mean the flea. Its oral apparatus, which I would name 
rostrulum, appears to consist of seven pieces. First are a 
pair of triangular organs, the Jamina, which together 
somewhat resemble the beak of a bird, and are affixed, 
one on each side of the mouth, under the antennz: these 
represent the mandibles of the perfect mouth *. Next, a 
pair of long sharp lancets (Scalpella), which emerge from 
the head below the laminz : these are analogous to maz- 
ille*: a pair of palpi, consisting of four joints, are at- 
tached to these near their base*, which of course are 
maxillary palpi. And lastly, in the midst of allis a 
slender setiform organ (ligula), which is the counterpart 
of the tongue. Rdosel, and after him Latreille, seem to 
have overlooked this last piece, since they reckon only 
sia pieces in the flea’s mouth ®: but the hand and eye of 
a N. Dict. d’ Hist. Nat. iv. 253. 
b Pirate VIL. Fic. 8, c’, d’, e', h!. © Ibid. c’. 
4 Tbid. d’. * Thid. h”. f Ibid. e’. 
® Rosel. i. 4. i. f 15. Latreille Gen. Crust. et Ins. iv. 365. 
