ARRANGEMENT OF THE EGG-MASS. 



225 



We have been for weeks with the insects where they were so thickly 

 ovipositing that the light, clay-yellow ground would be darkened by 

 them, and have laid on a closely -grazed sward for hours with specimens 

 in the act all around, and have repeatedly verified all that we have 

 here described. 



PHILOSOPHY OF THE EGG-MASS. 



" To the casual observer, the eggs of our locust appear to be thrust 

 indiscriminately into the hole made for their reception. A more careful 

 study of the egg-mass, or egg-pod, will show, however, that the female 

 took great pains to arrange them, not only so as to economize as much 

 space as possible, consistent with the form of each egg, but so as to best 

 facilitate the escape of the young locust ; for if, from whatever cause, 

 the upper eggs should fail to hatch, or should hatch later than the lower 

 ones, the former would offer an impediment to the exit of the young in 

 their endeavors to escape from these last, w^ere there no provision 

 against such a possibility. 

 The eggs are, indeed, most 

 carefully placed side by side 

 in four rows, each row gener- 

 ally containing seven. They 

 oblique a little crosswise of 

 the cylinder (Fig. 4, a). The 

 posterior or narrow end, 

 which issues first from the 

 oviduct, is thickened, and 

 generally shows two pale 

 rings around the darker tip (Fig. 4, h). This is pushed close against 

 the bottom of the burrow, "which, being cylindrical, does not permit 

 the outer or two side rows to be pushed quite so far down as the 

 two inner rows, and for the very same reason the upper or head ends 

 of the outer rows are necessarily tent to the same extent over the 

 inner rows, the eggs when laid being somewhat soft and plastic. There 

 is, consequently, an irregular channel along the top of the mass (Fig. 4, 

 c), which is filled only with the same frothy matter that surrounds 

 each egg, which matter occupies all the other space in the burrow not 

 occupied by the eggs. The whole plan is seen at once by a reference to 

 the accompanying figure, which represents, enlarged, a side view of the 

 mass within the burrow [a], and a bottom (b) and top (c) view of the 

 same, with the earth which adheres to it removed.'' 



This same quadrilinear arrangement of the eggs occurs, also, in the 

 egg-mass of the Ked legged and Lesser locusts, and in most of the spe- 

 cies of medium size which we have studied, including several different 

 genera. Yet it is by no means constant in the same genus, since, as we 

 shall see in Chapter XI, the eggs of Calopteuus differentialis (PI. IV, Fig. 

 1) are irregularly arranged. This irregular arrangement also occurs in 

 15 G 



Fig. 4: Egg-mass of Eocky Mountain Locust— a, from 

 the side, within burTow; h, from beneath ; c, Irom above, 

 enlarged. (After Kiley.) 



