INSECT'S STOMACH SNODGRASS 383 



Now that Ave have carrieil the yoiin<^^ insect through its development 

 to a point where it has acquired a complete di<restive apparatus, it 

 must not be supposed that the story is ended. The insect stomach 

 keeps on having historj^ to the end of its career. When the insect 

 has once consumed the embryonic food supply that was enclosed in 

 its stomach, it becomes from now on dependent upon food materials 

 taken into the stomach by way of the mouth. During postembryonic 

 life, therefore, the function of feeding becomes greatly augumented 

 since it must include the acquisition of food, the reduction of the food 

 mass, when necessary, to a form that may be taken into the mouth, 

 and its passage from the mouth to the stomach. All these accessory 

 functions involve the development of complicated mechanisms, a 

 study of which would be pertinent and extremely interesting in 

 connection with the stomach, but would lead us too far afield from 

 our immediate subject. 



The first use the young insect makes of its new feeding organs may 

 occur while it is still in the egg, for many insects, when the time for 

 emergence has arrived, swallow a liquid that fills the space between 

 them and the egg shell. This swells out the body and gives the insect 

 closer contact against the shell, so that by contortionistic movements, 

 or by pressing a spine or a sharp ridge on the head against the shell, 

 the latter is split and gives the confined creature a means of exit. 

 The head protrudes first from the egg, and then a still further infla- 

 tion of the body may be accomplished by swallowing air, giving an 

 increased pressure that assists in the final escape. Young insects 

 with well-developed jaws, however, may simply gnaw a hole in the 

 egg shell, and leisurely crawl out. Such insects are very likely then 

 to turn around and make their first meal on the rest of the shell. 



In the matter of eating, insects are hard to understand. They have 

 dietary laws that they follow scrupulously. While some of them will 

 cat almost anything, the majority confine themselves to some partic- 

 ular kind of food, and plant-eating species often refuse almost everv- - 

 thing but the leaves of a definite species of plant, though they will 

 make a few concessions in cases of emergency. As an example of 

 this trait we have only to recall the silkworm, which, as is well 

 known, must be fed on mulberry leaves or it will not spin a cocoon, 

 though when young it may be induced to nibble some lettuce or dan- 

 delion leaves to avoid starvation. This finickyness about food on the 

 part of insects is not a matter of " taste ", for they will not even try 

 the things they refuse. In this they resemble children, except that 

 they never grow out of their perversity. The insect mothers in 

 most cases know enougli to lay the eggs where their brood will find 

 on hatching the kind of food they will eat. Entomologists would 

 like to know the reason for these dietary whims of the insects; they 



