FUNCTIONS OF INSECTS. 21 



and semi-circles. These hooks, which are attached to the skin by a kind of retrac- 

 tile tubercles, serve as cramps to assist their motion on other bodies. The larvae of 

 such insects as undergo only a semi-metamorphosis, as Locusts, Crickets, and Cock 

 roaches, and those of insects that undergo no transformation, as the Spiders, Ticks, 

 and Mites, do not differ, with respect to their feet, from the perfect insects. In 

 this larva state many insects remain for months, others for a year, and some even for 

 two or three years. They are, in general, extremely voracious, oftentimes devour- 

 ing more than their own weight in the course of twenty-four hours. 



As soon as all their parts become 'perfected, and they are prepared to appeal 

 under a new fomi, called "a pupa or chrysalis* most species of insects fix^upon some 

 convenient place, for the performance of this arduous operation. This is generally a. 

 place where they are not exposed to danger ; for in their transformation, they have 

 neither strength to resist, nor swiftness to avoid, the attack of an enemy. That 

 Power which instructed the parents to deposit their eggs in a proper receptacle, 

 directs the offspring to the most secure and appropriate situation for their future 

 defenceless state. Some of them spin webs or cones, in which they enclose them- 

 fwlves ; others undergo their change in decayed wood ; and others conceal themselves 

 beneath the surface of the earth. Preparatory to the transformation, they cease to 

 take any food, and, for some days, continue in a state of inactivity. During this 

 time the internal organs are gradually unfolding themselves. When the completion 

 is at hand, many of them may be observed alternately to extend and contract 

 their bodies, in order to disengage themselves from the caterpillar skin. The hinder 

 parts are thoFf first liberated : when this is done, the animals contract, and draw 

 the skin up t /wards their head ; and, by strong efforts, they soon afterward push 

 it entirely off. In their chrysalid state they remain for some time, to all appearance, 

 inanimate ; but this is only in appearance, for, on being taken into the hand, they will 

 always be found to exhibit signs of life. It is singular that, in the changes of insecta, 

 the intestinal canal is frequently very different in the same individuals, as they pass 

 through the three states. 



As soon as the animal, within the shell of the chrysalis, has acquired strength 

 sufficient to break the bonds that surround it, it exerts its powers, and appears to 

 the world in a perfect state. For a little while it continues humid and weak ; but, 

 as the humidity evaporates, its wings and shell become hardened, and it soon after- 

 ward commits itself in safety to its new element. 



Some writers have conjectured that the antennae or horns of insects are their 

 organs of hearing; for it is evident, from various experiments, that insects are 

 possessed of this sense in a degree as exquisite as most other animals, although, 

 from their minuteness, we perhaps may never discover by what means. The antenna 4 , 

 however, seem little likely to answer the purpose of ears. These instruments, of 

 apparently exquisite sensibility, appear adapted to very different purposes, but to 

 purposes with which we may remain long unacquainted. 



The eyes of insects are formed of a transparent crustaceous set of lenses, so hard 

 as to require no coverings to protect them. These, like multiplying glasses, have 

 innumerable surfaces, on every one of which objects are distinctly formed; so 

 that, if a candle be held opposite to them, it appears multiplied almost to infinity on 

 their surfaces. Other creatures are obliged to turn their eyes ; but insects have 

 always some or other of these lenses directed toward objects, from what quarter 

 soever they may present themselves. All these minute hemispheres are real eyes, 

 through which every thing appears topsy turvy. 



M. Leeuwenhoek, with the aid of a microscope, used as a telescope, looked 

 through the eye of a Dragon-fly, and viewed the steeple of a church, which was two 

 hundred and ninety-nine feet high, and seven hundred and fifty feet from the place 

 where he stood. He could plainly see the steeple, though not apparently larger 

 than the point of a fine needle. He also viewed a house ; and could discern the front, 

 distinguish the doors and windows, and perceive whether the windows were open or 

 shut. Mr. Hook computed that there were fourteen thousand of these lenses in the 

 two eyes of a Drone ; and M. Leeuwenhoek reckons twelve thousand five hundred 

 and forty-four lenses in each eye of the Dragon-fly. The pictures of objects that 

 are delineated on these, must be millions of times less than those formed on the 



* The chrysalis is occasionally called Aurelia, Bean, or Cod. 



