﻿116 CLEMENS' SYNOPSIS OV 



attached to its upper and outer angles. The function of the labrum is to close the 

 space between the mandibles above, and to prevent the food from escaping in that 

 direction. At the external base of the mandibles are found the 



Antennae. These consist of a soft conical base, capable of being retracted or dilated, 

 having on its summit a short, cylindrical stalk consisting of two articles. The stalk 

 does not vary in form, nor in the number of its articles, throughout the entire order, 

 whatever may be the differences in the imago ; and the last article is furnished at its 

 summit with a long and slender seta. When disturbed, the larva can retract them 

 so as to conceal the organs almost entirely within the conical base ; but on resuming 

 motion they are first exserted, and during the act of feeding, although thrown out- 

 ward with every extension of the mandibles, they nevertheless lightly palpate the 

 leaf with their long setas. The ordinary use to which they are applied seems to be 

 that of simple palpation, and there is nothing in their ordinary employment, their 

 position or structure, as far as I have ever been able to determine, which justifies 

 the view that in the larval state they are the seat of any special sense. 



The middle and under portion of the head is marked by the absence of the walls 

 of the cranium, and is filled up by several parts which should be examined beneath 

 a lens to be easily distinguished. This portion, it will be perceived, can be naturally 

 divided into a central and two lateral parts. These lateral portions are what are 

 known as 



The Maxillary palpi. These organs lie along the inferior faces of the mandibles on 

 each side, and consist of three very distinct joints or articles, mounted on a large 

 soft base, which is indistinctly divided into two portions, and extends backward 

 nearly to the articulation of the head with the body. On the internal face of the 

 second joint will be found an additional tubercle, or mammiform body, ordinarily 

 concealed from view. This tubercle is the internal maxillary palpus, whilst the 

 exterior articles previously referred to, are the external maxillary palpus. These two 

 sets of palpi are merged into one stalk, and very much resemble in appearance an 

 additional pair of feet. The state of their development in the larva, as compared 

 with their condition and appearance in the head of the imago is very remarkable, 

 and appears to indicate a specialty of function in the embryo no longer required in 

 the perfect being, in which, except in some of the micro-lepidoptera, they are 

 represented by mere corneous rudiments, so unlike their former condition, that it is 

 difficult at first to believe them identical. In the absence of any experimental 

 observation directed to the determination of this special function, I can only say that 

 in feeding, the extremities of the external pair are closely applied to the leaf, and 

 appear to grasp it. Whether they have a more special function than that involved 

 in touch, must be ascertained hereafter. Between the lateral enlargement, forming 

 the bases of the maxillary palpi, is a soft central portion, the most posterior part of 



