INSECTS. 289 



The heads of all kinds of insects are good objects for the microscope. 

 This will be seen by reference to fig. 133, which shows the head of a 

 gnat, detached from the thorax, and drawn under a magnifying power 

 of 50 diameters, by the aid of the camera lucida ; the eyes cover nearly 

 two-thirds of the head ; and from the fore part are projected the pro- 

 boscis, lancets, antennae, &c. 



In the mouths and tongues of insects, the most admirable art and 

 wisdom are displayed ; and their diversity of form is almost as great as 

 the variety of species. The mouth is usually placed in the fore part of 

 the head, extending somewhat downwards. Many have their mouths 

 armed with strong jaws or mandibles, provided with muscles of great 

 power, with which they bruise and tear their food, answering to the 

 teeth of the higher animals ; and in their various shapes and modifica- 

 tions serving as knives, scissors, augurs, files, saws, trowels, pincers, 

 or other tools, according to the requirements of the insect. 



fig. 127. Eye of Fly, magnified 100 diameters. 



The tongue is generally a compact instrument, used principally to 

 extract the juices on which the insect feeds, varying greatly in its 

 length in different species. It is capable of being extended or con- 

 tracted at the insect's pleasure ; sometimes dexterously rolled up ; 

 taper and spiral, as in the butterfly ; tubular and fleshy, as in the 

 wasp. In fig. 126 the under-lip of the wasp is shown, with its brush 



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