THE REASON WHY IN NATURAL HISTORY. 



199 



Because they have been endowed with appe- 

 tites and with constitutions that enable them to 

 live upon and to enjoy corrupt matter. In this 

 point of view the maggots of flies are exceed- 

 ingly useful ; a dead carcass is speedily threaded 

 by them in every direction ; thus that corrupt 

 matter which, in a large mass, would poison the 

 air, is taken up in small portions by millions of 

 living bodies, and by them dispersed, and be- 

 comes innoxious. 



101. Why do we see, in tanks of rain water, 

 insects rising to the surface t 



Because numerous insects pass through their 

 first stages of existence in water, and among 

 them the common gnat. The gnats of the pre- 

 vious season having deposited their eggs on the 

 sides of the water-butt, the warm water develops 

 them, and the larvae of the gnats appear. 



1 02. Why do they continually rise to the surface 

 of the water t 



Because they require to breathe air, and there- 

 fore they come up to the surface, where elevating 

 the tube above the surface of the water, they are 

 enabled to breathe. 



103. Why do some appear to hai>e larger heads 

 than others t 



Those that have apparently larger heads, and 

 that breathe through tubes attached to their 

 heads, are in the pupa, or second stage of develop- 

 ment, and underneath the large shield by which 

 their heads are marked, their wings, feet, etc., 

 are being formed. 



104. Why, when the water is disturbed, do the 

 larva descend more rapidly than the pupa t 



Because the pupae are in a torpid condition, 

 awaiting the formation of their perfect organs. 



105. Why are the flies able to escape from the 

 water t 



Because, as their formation becomes perfected, 

 and the fluids of the body of the pupa become 

 absorbed in the production of the light texture of 

 the wings, etc., the body and its case become 

 lighter than the water, and rise and float upon 

 the surface. The pupa cnso then forms a natural 

 boat, from which the fly emerges, and, spreading 



its wings, enters upon the final state of its exist, 

 ence. 



This interesting metamorphosis may be seen going on ia 

 the summer time, in every pond, brook, and reservoir. A 

 fine sunny morning calls up millions of these little boats 

 from beneath the surface, and the diver within ttuit 

 wonderful little bell breaks its sealed doors, and flies awaj 

 to enjoy the bright sunshine. 



1 06. Why are beetles denominated " coleoptera "f 

 Because they have wings protected by horny 



sheaths ; the term coleoptera signifies wings in a 

 sheath. 



107. Why have beetles hard, horny wing cases t 

 Because they live underground, or in holes 



excavated in wood, etc. If, therefore, their wings 

 were not protected by a hard and firm covering, 

 they would be constantly liable to destruction 

 from the movement of the insect within hard and 

 rough bodies. 



The elytra, or scaly wings of the genus of scarabaeus. or 

 beetle, furnish an example of this kind. The true wing c 

 the animal is a light, transparent membrane, finer than th 

 finest gauze, and not unlike it. It is also, when expanded 

 in proportion to the size of the animal, very large. In 

 order to protect this delicate structure, and. perhaps, also 

 to preserve it in a due state of suppleness and humidity, a 

 strong, hard case is given to it, in the shape of the horny 

 wing which we call the elytron. When the animal is 

 at rest, the gauze wings lie folded up under this impenetra- 

 ble shield. When the beetle prepares for flying, he raises 

 the integument, and spreads out his thin membrane to the 

 air. And it cannot be observed without admiration, what a 

 tissue of cordage, i. e. of muscular tendons, must run in 

 various and complicated, but determinate directions, along 

 this fine surface, in order to enable the animal either to 

 gather it up into a certain precise form, whenever it desires 

 to place its wings under the shelter which nature has given 

 to them, or to expand again their folds when wanted for 

 action. 



In some insects, the elytra cover the whole body; in 

 others half ; in others only a small part of it ; but in all 

 they completely hide and cover the true wings. 



Many, or most of the beetle species lodge in holes in the 

 earth, environed by hard, rough substances, and have fre- 

 quently to squeeze their way through narrow passages ; in 

 which situation, wings so tender, and so large, could scarcely 

 have escaped injury, without both a firm covering to defend 

 them, and the capacity of folding themselves up under its 

 protection. 



1 08. Why have many of the beetle tribe large, 

 strong horns / 



Because as they live in holes in the earth, or 

 in excavations in wood, they use their horns to 

 dig out their places of retreat. 



