LEP1DOPTERA. 139 



pillars are concerned, any protuberance ; but in the tropical species 

 it is often armed with prickles, spikes, and extraordinary appendages. 

 They are provided with six small simple eyes, isolated from each 

 other. The mouth is armed laterally with a pair of very solid horny 

 mandibles, articulated by means of vigorous muscles, and moving 

 horizontally. It is the function of the mandibles, as with the jaws, to 

 divide the creature's food. On the middle of a broad under-lip one 

 may perceive a little elongated tubular organ, pierced with a micro- 

 scopic orifice. This organ is the spinning apparatus, which the 

 animal uses in fabricating the threads which it will one day require. 

 It is a tube composed of longitudinal fibres. It presents only one 

 orifice, cut obliquely, and capable of applying itself exactly to the 

 body on which the larva is placed. From the contractile nature of 



Fig. 94. Scaly legs of the Caterpillar of the Gipsy Moth (Liparis disfar). 



this organ and the form of its orifice, combined with the faculty the 

 insect possesses of moving it in all directions, result the great 

 differences we observe in the diameter and form of the threads. 



The external organs of the trunk and abdomen are the legs, the 

 spiracles, and various occasional appendages. The legs are of two 

 different kinds. The one, to the number of six, attached by pairs to 

 the trunk, are covered with a shiny cartilage, and armed with hooks. 

 These are the true legs. Fig. 94 represents, after Reaumur's "Memoire 

 sur les Differentes Parties des Chenilles,"* the scaly legs of the 

 caterpillar of the Gipsy Moth. The others are membranous, fleshy, 

 generally conical or cylindrical, contractile, and taking, according to 

 the will of the animal, very different forms. Fig. 95 represents, after 

 the same Memoir of Reaumur's, the different forms of the membranous 

 legs of the silkworm caterpillar. This plate gives a sufficiently good 



* Tome i., p. 164 j Plate III., Figs, i, 2. 



