20 GRASSHOPPERS IN GENERAL. 



LIFE-HISTORY OF THE DIFFERENTIAL LOCUST. 



Melanoplus differentialis Thos. 



This term, in its biologic sense, refers to the cycle of the individual 

 from the embryo until the fulfilment of its mission in the perpetuation 

 of its species and its retirement in favor of its progeny. The life of 

 the locust may be said to begin with the egg, in which the following 

 changes take place, and are noted under the head of 



EMBRYOLOGY. 

 By Mr. C. E. McCLUNG, Department of Zoology. Instructor in Embryology. 



Description of the egg. The arrangement of the eggs in the ovary 

 and the formation of the capsule have already been described ; it is 

 therefore only necessary to add a decription of the individual egg. 

 This, at the time of oviposition, is an ovate cylindrical body, about 

 5 mm. by 1.25 mm. in size, and of a bright yellow color, gradually be- 

 coming darker with age. The cylindrical form is not perfect, being 

 modified in such a manner that the anterior side of the egg, as it lies 

 in the mother insect, is flattened or even concave, while the opposite 

 side is equally convex (fig. 3). The two ends are very similar in 

 shape, each being bluntly pointed. 



tiff I 



FIG. 3. Eggs of Melanoplus differentialis. 

 (About five diameters.) 



The egg is protected by two coats, the exterior (chorion), a secre- 

 tion of the follicular epithelium ; and the interior (vitelline mem- 

 brane), the external, indurated portion of the egg substance. The 

 chorion is a close fitting shell, completely enclosing the ovum. It is 

 usually of a dull yellow color, and is marked over its entire surface 

 by ridges that cross each other in such a manner as to form an irreg- 

 ular hexagonal pattern. This is merely a cast of the lining of the 

 ovarian follicle, registered in its secretion. The chorion is, at first, 



