HOW TO KNOW THE IMMATURE INSECTS 



IMMATURE STAGES OCCUPY A LARGER PART OF THE LIFE 

 CYCLE. — The egg stage usually lasts but a few days, sometimes 

 even shorter, or the egg may hatch before it is laid, as is the case in 



the aphids. Many insects hi- 

 bernate in the egg stage in 

 which event the egg period 

 may last several months. 

 The growing stage is usual- 

 ly much longer than other 

 stages. The nymph of the 

 periodical cicada, Magici- 

 cada septendecim (L.) Lives 

 underground from 13 to 17 

 years as compared with the 

 30 or 40 days of its adult's 

 life and 6 to 7 weeks of its 

 egg stage. While some May- 

 flies live as adults for only 

 a few hours, their nymphal 

 stage is believed to occupy 

 three years. Many insects 

 spend their winter time in 



Fig. 6. Life cycle of the Japanese beetle, 

 Popillia japonica Newman. 



the pupal stage. In general, insects spend considerably more time in 

 their immature stages than they do as adults. 



LARVA AND NYMPH ARE HEAVIER FEEDERS. — When a survey 

 of the feeding habits of insects is made, the nymphs are usually found 

 to take the same kind of food as their adults. Larvae on the other 

 hand, usually feed differently and consume much more than their 

 adults. Take the order Lepidoptera as a good example; the caterpillars 

 eat a large quantity of food while a good number of moths do not feed 

 at all. 



ANIMAL EVOLUTION AND ADAPTION. — The zoological position 

 of some animals that are of degenerate form in the adult stages has 

 been established only by study of their embryonic and larval stages. 

 The larvae of barnacles show that these animals belong among the 

 crustaceans, and the peculiar parasitic barnacle, Sacculina can be 

 recognized as a crustancean only during its larval existance. Likewise, 

 the tunicates were found to be Chordates only by a study of their larval 

 characteristics. The adults of the Coniopterygidae look like aphids but 

 are regarded as Neuropteia because of the structures of their larvae. 

 The degenerate form of the aduhs gives no clue to their real position 

 among animals. Among insects there are many highly interesting 

 points to study in their evolution and adaptation. A knowledge of the 

 immature stages makes for a much clearer understanding in both of 

 these fields. 



