THE MINUTE ANATOMY OF THE LOCUST. 273 



EEPORT ON THE FINE ANATOMY OF THE LOCUST. 

 By Charles Sedgwick Minot. 



Most attention has been directed to the structure of the digestive and 

 reproductive organs. As the nature of the work required the use of 

 fresh materials from living specimens, and as I was unable to secure in 

 Boston living locusts from the Eocky Mountains, I have been obliged 

 to make my observations upon the New England species, Caloptenus 

 femur-rubrum. This, however, was a matter of little importance, for the 

 interior structure of the Eastern species is almost the same as that of 

 the Eocky Mountains, so that an anatomical description of the one ap- 

 plies almost word far word to the other. 



The investigation has been supplemented by some comparison with 

 other insects in order to determine, as far as the time at my disposal 

 allowed, in what points the structure of the locust is peculiar. 



I must first remark that every digestive canal in quadrupeds and 

 snails, as well as insects, consists of four physiologically distinct parts. 

 In the first place are found the organs for the mechanical seizure of the 

 food and swallowing, the jaws, mouth, and oesophagus. They serve to 

 seize the food, often to tear it up mechanically, and to transport it to 

 the interior of the body where it is to be digested. In the locust 

 these organs form a very complex system. In the second place 

 comes the stomach and parts where the digestive juices, properly so- 

 called, are secreted. In this portion the chemical nature of the food is 

 altered, rendering the mass suitable for absorption, which takes place 

 in the third part of the digestive canal. The second and third parts are 

 often not separated from one another, but we find in the wall of the in- 

 testine the organs of absorption and the digestive glands lying along- 

 side one another. Finally, in the fourth part, which is usually the termi- 

 nal end of the tract, the effete and indigestible masses are accumulated 

 and are finally expelled, being of no further use in the economy of the 

 animal. This terminal portion is usually called the rectum, the Latin 

 word for straight. This term was originally applied to man, in whom 

 this portion of the intestine is straight. Since then it has been em- 

 ployed for the analogous parts in animals, and often serves to designate 

 a structure which is very far from being straight. The rectum is well 

 nigh invariably supplied with muscles, by means of which it accom- 

 plishes the act of expulsion of the faeces. 



We will now proceed to describe the peculiarities of these four divi- 

 sions in the locust. We begin by an account of the general course of the 

 digestive tract from the mouth to the anus. 



The digestive canal begins in the head with the cavity of the mouth, 

 bounded inferiorly by the jaws and other appendages, and above by the 

 buccal plates ; it extends upward and forward from one-fifth to one- 

 fourth of the way through the head. Its walls are black, in this respect 

 entirely different from the rest of the canal. 

 IS Qi 



