THE EXTERNAL ANATOMY OF INSECTS 



45 



The gdlea or helmet (/) is the second in prominence of the appendages 

 of the maxilla. It consists of one or two segments, and is joined to the maxilla 



mesad of the palpus. The galea varies greatly 

 in form : it is often more or less flattened, with 

 the distal segment concave, and overlapping 

 the lacinia like a hood. It was this form that 

 suggested the name galea or helmet. In other 

 cases the galea resembles a palpus in form (Fig. 

 57). The galea is also known as the outer lobe, 

 the upper lobe, or the superior lobe. 



The lacinia or blade (g) is borne on the mesal 

 (inner) margin of the subgalea. It is the cutting 

 or chewing part of the maxilla, and is often 

 furnished with teeth and spines. The lacinia is 

 also known as the inner lobe, or the inferior lobe. 



The digitus or finger (Ji) is a small appendage 

 sometimes borne by the lacinia at its distal end. 

 In the Cicindelidae it is in the form of an articu- 

 lated claw (Fig. 57) ; but in certain other beetles 



it is more obviously one of the segments of the 

 Fig. 57.-Maxilla otdcindela. maxiUa (pigs> 55 and 56)> 



The labium or second maxilla. The labium or under lip (Fig. 53), 

 is attached to the cephalic border of the gula, and is the most ventral 

 of the mouth-parts. It appears to be a single organ, although some- 

 times cleft at its distal extremity; it is, however, composed of a pair 

 of appendages grown together on the middle $ne of the body. In the 

 Crustacea the parts corresponding to the labium of insects consists of 

 two distinct organs, 

 resembling the 

 maxillae; and in the 

 embryos of insects 

 the labium arises as 

 a pair of append- 

 ages. 



In naming the parts 

 of the labium, entomo- 

 logists have usually 

 taken some form of it 

 in which the two parts 

 are completely grown 

 together, that is, one 

 which is not cleft on 

 the middle line (Fig. 



58). I will first describe such a labium, and later one in which the division 

 into two parts is carried as far as we find it in insects. 



Fig. 58. Labium of Harpalus. 



