448 EXTERNAL ANATOMY OF INSECTS, 
reduced to three. The Libellulina may almost be re- 
garded as having no maxillary palpi, since they exhibit 
no organ that is distinctly palpiform. It seems to me 
that the upper lobe of their maxilla, which articulates 
with the stalk in the same manner as a feeler, may be 
regarded as an instance in which that lobe and the feeler 
coalesce into one; and the mucro that proceeds from 
the lobe has the aspect of an emerging feeler, and corre- 
sponds somewhat with the labial one above noticed +. 
In the remainder of the Neuroptera and the Trichoptera, 
the prevailing number is jive and three. In the latter 
there are exceptions, which will furnish good characters 
for genera. In the Lepidoptera we find two, and some- 
times three, the maxillary being very minute’. The 
Diptera Order presents two tribes in this respect quite 
distinct fron each other. The most natural number of 
joints in the maxillary palpi of the Tipulide, Culicide, 
&c. is four or five: the last joint, however, in Tipula, 
Ctenophora, &c. like that of the antennze in Tabanus L., 
appears to consist of a number of very minute joints*; 
but in the Aszlid@ and Muscida, &c., the number wo 
seems to be most prevalent’. The /abzal palpi in this 
order are obsolete.—As to shape, the maxillary palpi, 
as well as the labial, are usually filiform; but in the 
weevil tribes (Rhyncophora) they are most commonly 
very short and conical*; in the chafers (Petalocera) 
they usually are thickest at the apex‘; in Megachile and 
* Prare Vi. Pic. 12. b’. £". 
b Tbid. Fic. 13. h’. Savigny Anim. sans Vertebr. I. 1, 29—. 
t. i—iil. 6. © De Geer vi. t. xix. f. 4. d. 
@ Ibid. fix. f. 8. bb. t. xii, f, 20. b. t. xiv. f. 15. Gi. 
© Pratr XXVI. Fic. 6. f Ibid. Fie. 5. 
