STRUCTURE OF LARV.E. 185 



the larva will by no means lead us to a correct idea of the 

 mouth of the imago : thus the jaws of the caterpillars of 

 butterflies are as robust, and not very unlike those of the 

 larva? of beetles ; but the mouth of the butterfly consists of a 

 slender spiral and tubular apparatus for sucking up honey, 

 whilst that of the beetle retains much of the general appear- 

 ance of the mouth of the larva. There are some peculiari- 

 ties in the structure of various organs of the mouth, which 

 it may be interesting to notice. Thus the jaws of the ant- 

 lion, and of the larva? of the predaceous water beetles, are 

 very long, slender, curved, and sickle-shaped, having a small 

 longitudinal aperture near the extremity, which communicates 

 with an internal canal, through which the juices of the prey of 

 the insect pass. Another remarkable peculiarity exists in 

 the elongated elbowed structure of the lower lip of the larvae 

 of the Libellulidce (dragon-flies), forming a mask over the 

 face, and which is employed like an arm furnished with 

 claws for seizing their prey. Again, in those larvae which 

 spin for themselves silken cocoons, in which they undergo 

 their transformations, the lower lip is furnished at its extre- 

 mity with a minute and slender organ (fig. 21, i), which 

 Kirby and Spence have aptly termed the spinneret (fusulus), 

 composed of several longitudinal slips, alternately corneous 

 and membranous, whereby the insect has the means of con- 

 tracting the tube, which terminates in a single orifice, and 

 through which it emits its silken threads, which, although 

 elaborated in two distinct silk tubes, unite previous to their 

 emission from the orifice of the tube. Some larvae, indeed, 

 spin a silken thread for the formation of cocoons from a 

 distinct apparatus at the extremity of the body. 



I now pass to the description of the other segments of 

 the body of larvae, and the organs of motion and other ap- 

 pendages with which they are provided. Generally speaking, 

 these segments, which are typically twelve in number, are of 



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