INSECTS. 105 



to attack all dead or putrefying materials, and thus 

 aid in the removal of substances, which by their 

 accumulation might prove a constant source of annoy- 

 ance and mischief. Such differences in their nature 

 demand, of course, corresponding diversity in the 

 construction of the instruments employed for pro- 

 curing nourishment ; and, accordingly, we find in 

 the structure of the mouths of these little beings 

 innumerable modifications, adapting them to different 

 offices jaws armed with strong and penetrating 

 hooks for seizing and securing struggling prey sharp 

 and powerful shears for clipping and dividing the 

 softer parts of vegetables ; saws, files, and augers, for 

 excavating and boring the harder parts of plants, 

 lancets for piercing the skin of living animals, siphons 

 and sucking-tubes for imbibing fluid nutriment all 

 these, in a thousand forms, are met with in the insect 

 world, and thus provide them with the means of 

 obtaining food adapted to their habits, and even of 

 constructing for themselves edifices of inimitable 

 workmanship. 



The mouths of insects may be divided into two 



FlG. TO. PARTS OF THE MOUTH OF AX INSECT. 



great classes, those which are adapted for biting, 

 forming what is called a perfect or mandibulate 

 mouth, and those which are so constructed as only to 

 be employed in sucking, constituting the suctorial or 

 hausteuate mouth. It is in the former of these that 

 all the parts are most completely developed. The 

 perfect mouth of an insect consists of an upper and 

 an under lip, and four horny jaws. The upper lip 

 (labrum) (Figs. 70, 71, a) is a convex horny plate, placed 

 transversely across the upper margin of the cavity in 

 which the jaws are lodged, so that when the mouth 



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