464 EXTERNAL ANATOMY OF INSECTS. 
sion. ‘This part consists of five pieces: viz. a minute, 
long, conical piece, commonly very slender, which covers 
the base of the promuscis, and represents the labrum ; a 
jointed sheath (vagina), consisting of either three or four 
joints, the analogue of the /abiwm, and four slender rigid 
lancets (scalpella), the two exterior ones, according to 
M. Savigny, representing the mandibles, and the inter- 
mediate pair the maxille>. By the union of these four 
pieces a suctorious tube is formed, which the animal in- 
serts into the substance, whether animal or vegetable, 
the juices of which form its nutriment. These pieces 
are dilated at their base, and serrated at their apex; and 
the two central ones, though at their origin they are 
asunder, form one tube, which has often been mistaken 
for a single piece. A pharynx and tongue have been 
discovered by M. Savigny in this apparatus ; who thinks 
that in Nepa there are also rudiments, but very indis- 
tinct, of labial palpi; so that the maxillary palpi seem 
to be the only part absolutely wanting °. 
The Promuscis when at rest is usually laid between 
the legs; but when employed, in most cases its direction 
is outward. In the genus Chermes the origin of the 
promuscis has been supposed to be in the breast ; but if 
closely examined, this anomaly in nature will be found 
not to exist. If you take one of these insects, the first 
thing that strikes you upon inspecting the head, is a 
pair of remarkable conical processes into which the front 
appears to be divided. Look below these, and you will 
there discover the upper-lip: and from this you may 
@ Prate VI. Fie. 7. a’. 
» Tbid. Labium b’. Mandibulz c!. Maxilla d’. 
£ 
* Savigny Anim. sans Vertebr. 1. i. 37. 
