ANATOMY. 



insect, so starved that it has not largely increased its 

 flesh, will, nevertheless, carry on its accustomed molts. 

 In the case of winged insects having incomplete meta- 

 morphosis, the developing wings show as pads several 

 stages before the adult. In those having complete meta- 

 morphosis, even the full-grown larvae have no external 

 indication of wings ; these appear externally after the molt 

 which results in the pupa and, when the pupa molts, out 

 steps the winged adult. 



The Inside Mention has been made of the hard 



("chitinized") skins of insects: it is their 

 skeleton and their muscles are attached to it. In man, 

 the blood is sent to the lungs for a load of oxygen 

 which it then carries to the tissues. Insects do things 

 more directly; air is conducted to all parts of the 

 body by means of a system of tubes called tracheas. 

 This system usually has a number of outside openings 

 (spiracles) placed along each side of the body, but there is 

 none on the head. Insects do not breathe through their 

 mouths. Blood completely fills the body cavity and is 

 kept in motion by means of a "heart" which is merely a 

 pulsating tube open at both ends. The central nervous 

 system is a double, longitudinal series of ganglia connected, 

 one with another, by cords. There is no brain, strictly 

 speaking, for the ganglia in the thorax seem to be about as 

 important as those in the head. Nerves run from each 

 ganglion to nearby parts of the body. Most insects seem 

 to smell by means of their antennas and some to hear 

 with the same organs, but the location of "ears, " if "ears" 

 exist, is various and not always known. 



The Outside All insects are divided into three parts: 



head, thorax and abdomen. In some 

 larvae these parts are not distinctly marked off, but 

 usually there will be no difficulty in recognizing the 

 head. The thorax bears the wings, if any, and the 

 true legs, if any. No insect ever has more than three 

 pairs of true legs, and no other creatures which the amateur 

 is likely to notice and confuse with insects have as few 

 as three pairs of legs. The part of the thorax which bears 



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