138 



PHYSIOLOGY OF INSECTS. 



or crawling the six true legs are brought into action, 

 clasping or embracing the twig, as shown in the figure of 

 the sjDurge hawk-moth caterpillar, at page 90. 



It is not, however, in caterpillars that the entomologist 

 will find this division into segments of the greatest impor- 

 tance : in the perfect insect the modification of these seg- 

 ments, and the appendages which they bear, supphes the 

 only means by which gi'oups of insects, and even individual 

 species, can be distinguished from each other. The most 

 r-~\r\ simple form of a perfect insect will best ex- 

 A \ — (j \y hibit the existence of these segments. In the 

 giant Phasma, or walking stick as it has 

 been termed, — a large and singular insect, 

 inhabiting Brazil and other hot climates, — the 

 division into segments is not only more ob- 

 vious, but from the entire absence of wings 

 more satisfactorily defined than in any insect 

 inhabiting this country ; the author has there- 

 fore selected it to show the thirteen segments 

 in what may be termed their most simple form. 

 In this, as in the preceding figure, each seg- 

 ment is separated from its neighbours, and it 

 U will be observed that the 1st, 2nd, 3rd, and 4th, 



u ~~ a bear, each of them, an appendage on each 



Y ai side, a, i, u, y, making four pairs of appen- 



' dages ; those on the first segment are antennae ; 



Phasma. ^^ remainder are legs. These animals crawl 



on the ground or on trees, feeding on leaves, &c., and so 



much resemble dried sticks or living twigs, as to deceive 



the birds, which would othei*wise prey on them. 



Very similar in form and appearance to Phasma is 

 another large and very singular group of insects, called 

 Mantis or walking leaves, and these are usually provided 

 with wings or additional appendages attached to the third 



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