DEVELOPMENT AND METAMORPHOSIS. 33 



or mature insect are to be expressed in one term- 

 metamorphosis. 



Development with no Metamorphosis. 



If an insect undergoes no bodily changes after hatch- 

 ing from the egg, there is no metamorphosis. This is 

 true for only a very few insects, as the thrips and the fish 

 moths. These insects, when they hatch from the eggs, 

 look exactly like their parents except that they are smaller. 

 And they come to maturity by a series of moults after 

 each one of which the body is larger; no new organs ap- 

 pear, there is simply an increase in bulk until the size of 

 the parent is reached, then the moults stop. 



Complete Metamorphosis. 



But for other insects than those mentioned, changes 

 take place during the period of immaturity, changes 

 involving body form or life habits and conditions, or both. 

 The changes may affect only slightly the body form, the 

 life habits and conditions remaining practically unchanged ; 

 we speak of this mode of reaching maturity as incomplete 

 metamorphosis. Where these changes include not only 

 changes in body form, but also in the life conditions and 

 habits, this series of changes we call complete metamor- 

 phosis; it comprises the four stages of egg, larva, pupa, 

 and adult. 



Besides these three modes of attaining maturity, 

 a few insects, one family of beetles, the blister beetles, 

 scale insects, and a few parasitic hymenopters, multiply 

 the larval stage several times; the blister beetles at their 

 different moults appearing with markedly different larval 

 bodies, but the last one finally merging into the familiar 

 resting pupa of its kind. (Fig. 16.) This last mode is 



