488 THE MICROSCOPE. 



curiously-formed proboscis ; this latter is covered over with 

 feathers or scales. A magnified view of one of these feathers 

 is seen at No. 3. Another scale from a Gnat's wing is 

 magnified 500 diameters, fig. 249, No. 7. The proboscis 

 is protected on either side by an- 

 tennae, or feelers. Any one who 

 takes the trouble to watch the 

 operations of the female (fig. 244), 

 when she is about to make her nest, 



Fig, ^.-Female Gnat deposit- must be mucl]L Struck With the 



ing her eggs. ingenuity and admirable instinct 



this little creature displays. 



The bodies of insects are covered with a hard skin ; this 

 answers the purpose of an internal skeleton, and is one of 

 their chief characteristics. All animals, and most fishes, 

 have an internal skeleton of bones, which give attach- 

 ment to muscles : but the interior of an insect is a 

 soft mass, and the muscles are affixed to the exterior 

 casing or horny skin ; this answers all the purposes of 

 bone, connecting the various parts, maintaining them in 

 their proper places, and at the same time it forms a perfect 

 covering to the body. In some insects this horny skin is 

 remarkable for its strength, as in the Beetle tribe, many of 

 which are exceedingly curious in their construction. 



The family Phryganeidce, the larvae of which are aquatic, 

 present almost as little resemblance to the imago as those 

 of some metabolous insects. They are long, softish grubs, 

 furnished with six feet, and with a horny head armed with 

 jaws, generally fitted for biting vegetable matters, although 

 some appear to be carnivorous. To protect their soft 

 bodies, which constitute a very favourite food with fishes, 

 the larvaa are always enclosed in cases formed of bits of 

 straw and sticks, pebbles, and even small shells. The 

 materials of these curious cases are united by means of 

 fine silken threads, spun like those of the caterpillars of 

 the Lepidoptera, from a spinnaret situated on the labium. 

 ' In increasing the size of its case to suit its growth, the 

 larva is said to add to the anterior part only, cutting off a 

 portion of the opposite extremity. When in motion, the 

 larva pushes its head and the three thoracic segments, 

 which are of a harder consistence than the rest of the 



