96 



Marvels of Insect Life. 



f 



Of course, the development of the 

 Insect, of whatever kind, begins in the ^^^g. 

 When the larva breaks the egg-shell and 

 creeps out, it has passed through one stage 

 of existence and entered upon a second. 

 All kinds of Insects are not equally de- 

 veloped when they arrive at this point. 

 The newly hatched grasshopper is a more 

 highly developed Insect than the newly 

 hatched caterpillar : a parallel condition 

 to what we find among young birds, where 

 one is born naked, blind, and incapable of 

 picking up its food, whilst another is well 

 clothed with down, has its eyes open, and 

 can find its own food at once. 



Most Insects after they leave the egg 

 moult their skin at intervals. Caterpillars 

 as a rule cast their skin five times, and the 

 intervening periods are known as instars. 

 The fifth moult reveals the chrysalis or 

 sixth instar, and the butterfly or moth is 

 the seventh instar. Including the egg, we 

 thus have eight stages instead of the four 

 that are commonly attributed to the 

 butterfly or moth. But in these first five 

 instars of butterfly existence the changes often amount to little more than an increase 

 of size. Sometimes, however, there are changes of colour and ornament to help 

 to hide the increasing bulk of the caterpillar. What are popularly known, then, 

 as the four stages of Insect life must be understood to refer only to those moults 

 where the entire external form of the Insect has suddenly undergone a great change 

 ■ — in a word, transformation. 



Now in the case of an Insect like the grasshopper that only moults without 

 showing us any startling changes of form, we cannot speak of caterpillar stage 

 and chrysalis stage. We may speak of it when it leaves the egg up to the time 

 when the hard, packed-up buds of the wings appear, as the larval stage ; but an 

 Insect that has no resting period, and is actively crawling and leaping through 

 life without a break is properly called a nymph. Many beetle larvae are incapable 

 of walking, and to these the term grub is usually applied ; some, however, are 

 active, and here again the word larva is the more appropriate. 



The third distinct stage in the evolution of the butterfly or moth is properly 

 termed a pupa. In common parlance it is more usual to speak of it as a chrysalis : 

 a strange instance of the public having selected the more difficult of two 

 alternative words. The term, though now pretty generally ap])lied to the resting 

 stage of butterflies and moths (and other Insects), is strictly applicable only to the 

 gilded pupse of certain butterflies. There are two distinct types of pupa. In one, all 



Photo 6y] \H. S. Cheavin. F.R.M.S 



Nymph of a Lace-Bug. 



This photograph illustrates the active stage which corresponds 

 with the inactive chrysalis of the butterfly. In Insects thus 

 active throughout life there is no real metamorphosis. Here 

 the wings are seen to be only half -grown. 



