INSECTS 



285 



insects. The change by which a larva becomes an adult 

 is known as its metamorphosis. The adult form of an 

 insect is known as its imago, and the epimorpha are said 

 to have an incomplete metamorphosis. Other insects have 

 a larval stage and a more or less complete metamorphosis. 

 (2) In dragonflies and certain other insects, at the stage 

 in which the metamorphosis takes place the animal is free 

 and active and is known as a nymph. Such insects are 



Fig. 191. — The Turnip Flea-beetle (Haltica nemorum). 

 From Theobald. 



±, Adult, magnified ; 2, true length and wing expanse ; 3, adult 

 feeding on leaf ; 4, egg, natural size ; 5, the same magnified ; 

 6, 7, tunnel made by larva in leaf; 8, 9, larva, natural size arid 

 magnified ; 10, ti, natural size and magnified view of pupa, 

 which lies in soil. 



This very destructive insect feeds, as larva and adult, on 

 the leaves of turnips, cabbages, broccoli, and other Crucifera. 

 It has many broods in the year, the last hibernating under 

 stones, etc. Its worst damage is done to seedlings. Paraffin, 

 or a mixture of soot and lime are remedies. 



Hemimetabola. (3) In the rest of the insects, including 

 beetles, ants, bees and wasps, flies and butterflies, the 

 insect passes through an almost motionless stage known as 

 the pupa. These insects are called Holometabola, and in 

 them the metamorphosis is very complete. The body of 

 the pupa undergoes a profound reorganisation. A few of 

 the most important systems of organs, such as the repro- 

 ductive, nervous, and circulatory, last on, but the others 

 are devoured by a phagocytic action (p. 100) of the blood 

 corpuscles and re-formed by the growth of certain clumps 



