THE REASON WHY IN NATURAL HISTORY. 



495 



tion. and be selected by the naturalist to exhibit the marvel- 

 lous works of the creation. The terms given to these in- 

 sects lead us to expect interesting particulars concerning 

 them, since they have been divided into vagrants, hunters, 

 swimmers, and water spiders, sedentary, and mason -spiders, 

 thus evincing variety in their condition, activity, and mode 

 of life; and \\ecannot be surprised to lind them varying in the 

 performance of their vital functions (as, for example, in their 

 mode of breathing), as well as in their extremities and in- 

 struments. Of these instruments the most striking is the 

 apparatus for spinning and weaving, by which they not 

 only fabricate webs to entangle their prey, but form cells 

 for their residence and concealment; sometimes living in 

 the ground, sometimes under water, yet breathing the 

 atmosphere. Corresponding with their very singular organ- 

 ization are their instincts. We are familiar with the watch- 

 luln s and voracity of some spiders, when their prey is 

 indiv ated by the vibration of the cords of their net-work. 

 Others have the eye and disposition of the lynx or tiger, 

 and after crouching in concealment, leap upon their victims. 

 Some conceal themselves under a silken hood or tube, six 

 eyes only projecting. Some bore a hole in the earth, and 

 line it as finely as if it were done with the trowel and 

 mortar, and then bang it with delicate curtains. A very 

 extraordinary degree of contrivance is exhibited in the trap- 

 door spider. This door, from which it derives its name, 

 has a frame and hinge on the mouth of the cell, and is so 

 provided that the claw of the spider can lay hold of it, and 

 whether she enters or goes out. the door shuts of itself. Gut 

 the water-spider has a domicile more curious still; it is 

 under water, with an opening at the lower part for her exit 

 and entrance: and although this cell be under water, it 

 contains air like a diving-bell, so that the spider breathes 

 the atmosphere The air is renewed in the cell in a man- 

 ner not easily explained. The spider comes to the surface ; 

 a bubble of air is attracted to its body; with this air she 

 descends, and gets under her cell, when the air is disen- 

 gaged and rijes into the cell; and thus, though under 

 water, she lives in the air. There must be some peculiar 

 property of the surface of this creature by which she can 

 move in the water surrounded with an atmosphere, and live 

 under the water breathing the air. 



The chief instrument by which the spider performs these 

 wonders is the spinning apparatus. The matter from 

 which the threads are spun is the liquid contained in cells; 

 the ducts from these cells open upon little projecting teats, 

 and the atmosphere has so immediate an effect upon this 

 liquid, that upon exposure to it the secretion becomes a 

 tough and strong thread. Twenty-four of these fine strands 

 form together a thread of the thickness of that of the silk- 

 worm. We are assured that there are three different sorts 

 of material thus produced, which are indeed required for 

 the various purposes to which they are applied as, for 

 example, to mix up with the earth to form the cells; to line 

 these cells as with fine cotton; to make light and floating 

 threads by which they may be conveyed through the air. as 

 well as those meshes which are so geometrically and cor- 

 rectly formed to entrap their prey. 



66. Why have many insects a great number of 

 yes t 



Because the orb of the eye is n:;cd ; there is 

 therefore placed over the eye a muitiple-lense, 



which conducts light to the eye from every 

 direction ; so that the insect can see with a 

 fixed eye as readily as it could have done with a 

 moveable one. As many as fourteen hundred 

 eyes, or inlets of light, have been counted in the 

 head of a drone-bee. The spider has eight eyes, 

 mounted upon different parts of the head : two 

 in front, two in the top of the head, and two on 

 each side. 



67. Why do certain butterflies lay their eggt 

 upon cabbage leaves t 



Because the cabbage leaves are the food of the 

 young caterpillars ; and although the butterfly 

 does not subsist herself upon the leaf, she knows 

 by instinct that the leaf will afford food to her 

 future young ; she therefore lays her eggs where 

 her young ones will find food. 



This explanation applies to many insects that lay their 

 eggs upon other plants. 



68. Why have insects long projections from their 

 heads, like horns or feathers t 



Because those organs (the antennae), are those 

 through which some insects hear and others 

 feel ; and the projecting of these antennae from 

 their bodies probably enables them to hear or 

 feel more acutely while their wings are in 

 motion, without the interference of the vibrations 

 of their wings. 



69. Why can gossamer spiders float through tht 

 air f 



Because, having no wings, and being deficient 

 in the active muscular powers of other spiders, 

 they have been endowed with the power of 

 spinning a web which is so light that it floats in 

 the air, and bears the body of the gossamer 

 spider from place to place. Each web acts as a 

 balloon, and the spider attached thereto is a 

 little aeronaut. 



70. Why do crickets make a pe'culiar chirping 

 sound t 



Because they have hard wing cases, by the 

 friction of the edges of which they cause their 

 peculiar noise, to make known to each other 

 where they are, in the dark crevices in which 

 they hide. 



71. Why has the glow-worm a brush attached to 

 its tail? 



Because it is necessary to keep its back very 

 clean, that the light which its body emits may 

 not be dimmed. 



