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and expand themselves on the arrival of the spring, their appearance increases, till having 

 approached the period when they are to forsake their former habitations and become 

 inhabitants of the air, these wing-cases have then arrived to their due size, and carry the 

 appearance in which they are here seen. They are all of them, from the largest to the 

 smallest, armed with a strong offensive weapon, which serves them, and is indeed the 

 means they are endued with, for obtaining their food. This weajion being placed in 

 the under part of the head, just beneath the mouth, I have displayed in Fig. 1. and 3. of 

 Plate 47. where it appears just in the same manner as when they are endeavouring to 

 catch their prey. In the largest figure at 1. and also in Fig. 2. it appears contracted and 

 shut up, as when at rest. The strength and power that these animals discover in the use 

 of this instrument is very singular and extraordinary. There are two joints to it, one 

 about the middle, the other underneath the mouth, close to the throat ; and in some 

 (particularly all those of Fig. 2.) when it is closed or contracted, it appears fastened to 

 the face of the creature, by fitting it so exactly as to form a perfect mask ; covering the 

 mouth, and reaching almost as high as the eyes. In others it is made to fit only the under 

 part of the mouth, and when at rest is drawn up close underneath it. At the extremity 

 of those that are extended may be observed two very strong and remarkable fangs ; that, 

 shutting over each other, form a pair of forceps, of such strength that few, if any of their 

 captives, can escape if once inclosed therein. [This organ is the greatly developed lower 

 lip of the larva, and is analogous in its structure to the same part in the imago.] 



" The motion of these creatures in the water, particularly those of the largest size, is 

 very slow ; seldom exercising any swiftness or activity, unless they are disturbed and 

 threatened with danger, in which case they can transport themselves to places of more 

 security with the quickness or agility of a fish ; but, in general, they appear to have so 

 little inclination to move, that I have often seen them (I mean those that I have kept in 

 glass bowls) remaining in their respective places above a week together, and could not 

 discover the least motion in them, unless under the circumstance above mentioned, or when 

 they had seen their prey and were advancing to seize it. The caterpillars of Fig. 1. 1. 

 and 3. generally fix themselves to some little stick or straw, &c. that they find in the 

 water, and there remain, as I said before, without stirring. Those of Fig. 2. are more 

 frequently seen in motion among the thickest part of the roots and plants that grow there, 

 routing and searching for those small animals inhabiting that part, which are their proper 

 food. This aversion to motion, so apparent in those of No. 1. and 3., appears to me to be 

 the effect of an extraordinary cunning and sagacity ; and may be considered as the prin- 

 cipal means by which they obtain their prey : for while they continue thus motionless in 

 the water, the small animals, who constitute their proper food, approach them with less 

 fear than they would otherwise do, not suspecting their grand enemy lies upon the watch 

 to seize them the moment thev come within his reach ; but no sooner has their insensibility 

 of danger brought them within a small distance of those destructive weapons (mentioned 

 before, being placed under their mouths) but that very instant they dart upon them with 



