EXPERIMENT STATION BULLETINS. 



281 



arating into two, they often remain joined together, forming a sort of chain. 

 Under suitable conditions of light and heat, these minute organisms cause 

 rapid fermentation and the decompositiou of nitrogenous matter. 



A GLIMPSE AT THE TRANSFORMATIONS AND HABITS OP INSECTS. 



What is an insect? Most people, were they to reply to this question, 

 would say: An insect is a small creature that can walk and fly and is 

 found everywhere. Ask a student who has studied insects more closely , 

 and he will tell you an insect is a small animal with six legs in the adult 

 stage, which has a distinct head, thorax, and abdomen that are held together 

 merely by muscles. Further, he can tell us that an insect has no bony 

 skeleton like the higher animals, but a homy covering with all the mus- 

 cles, digestive organs, etc., inside of this shell-like armor. By this defini- 

 tion we have greatly restricted the number of animals in our class of 

 insects; yet, insects proper, if they could be counted, would undoubtedly 

 outnumber all other animal life on the earth, even including man. How 

 essential it is then that we should know more of them and their habits 

 and the best methods for their control, especially when they destroy so 

 many million dollars' worth of property annually. 



TEANSFORMATIONS. 



i^ and hard 

 "^ There 



In their development, most insects will be found to pass through four 

 different forms — the egg, larva, pupa, and imago. 



The Egg (A and 

 B of Fig. 1).— We 

 are not as likely to 

 find the egg as we 

 are the other three 

 stages, because in- 

 sect eggs are usu- 

 ally very - minute 

 to find, 

 are some, 

 though, that may 

 easily be seen, as is 

 the case with the 

 slender white eggs 

 of the currant saw- 

 fly, which may be 

 found in the spring 

 by examining the 

 central ridge on 

 the under side of the new currant leaves, well in toward the center of the 

 bush. Eggs, when placed in a bunch on leaves or twigs, are more readily 

 seen, and it is a good plan to crush all such egg clusters, as they will usu- 

 ally prove to be the eggs of a pest rather than those of a friend. The egg 

 stage with most insects lasts from a few days to a week or two, though 

 quite a number remain over winter in this stage. 

 36 



Fig. 1.— a, 6, Eggs; c, d, Larvae; e, Pupa; /, Imago. 



