﻿NORTH AMERICAN SPHINGIDiE. 119 



palpi, are placed on the inner base of the filaments, one of which may be seen figured 

 in the detached portion of a filament in fig. 3. These latter organs are some- 

 times well developed, and from three to five-jointed in other families, but their origin 

 is always at the inner base of the tongue. In the middle of the head, and overhang- 

 ing the exterior base of the tongue [fig. 3, I.) is a minute plate or immovable scale, 

 which corresponds to the labrum or upper lip; and the mandibles or upper jaws are 

 the most exterior corneous processes, (mx.) now fixed and useless. The labial palpi, 

 however, which we found in a mere rudimental state in the larva, become very noticea- 

 ble organs in the imago. They are not delineated in any of the figures, having been 

 removed to show parts less developed, but the points of their attachment are seen in 

 fig. 4, p. where there are two holes or foramina. They are never more than 

 3-jointed, and the articulations are more or less completely concealed by a covering 

 of scales or hairy scales. They serve principally to deepen the cavity for the recep- 

 tion of the coiled tongue, but their real function is doubtless not confined to a use so 

 purely physical, for throughout the order there does not appear to be any relative 

 development in the two organs. I have never attempted to dissect these organs, and 

 their internal structure might throw some light on the nature of their functions. 

 The concurrent development of these organs and the tongue in the imago, whilst 

 those parts which predominate in the larva are usually so completely atrophied, 

 seems to point to a higher functional condition of the parts in the imago than the 

 embryo. 



These are all the parts of the oral apparatus in the embryo and imago, but in 

 addition, I wish simply to direct attention to the existence of a foramen at the base 

 of the remains of the mandibles (fig. 3,/.) and sometimes placed somewhat higher on 

 the front. It is noticeable only when the . head has been denuded of scales, and in 

 many instances is quite large and elliptical, and is especially observable in the Sa- 

 turniidod, in Gossus, besides most members of the present group. A portion of a split 

 bristle with a fine point, can easily be introduced through this foramen into the head. 

 When this is sought for by dissection it is found between two corneous plates ; and 

 during a single examination of this kind, I found here quite a large tracheal trunk, 

 which I think originated at this external opening. I would not assert this by any 

 means positively, for I ruptured it unfortunately before I could certainly ascertain 

 the fact, and have not since repeated the dissection. If this be true, however, we 

 have here a pair of cephalic stigmata^, and the question arises whether their function 

 is a special one, or similar to the stigmatse in other portions of the body. I have 

 been too much engaged in other studies, since first making this observation, to enable 

 me to elucidate fully this portion of insect structure ; but my own supposition is 

 that it is connected with, or forms the seat of the function of smell. There is not the 

 least trace of this opening in the head of the larva, and as it has not heretofore 



