632 REPORT UNITED STATES GEOLOGICAL SURVEY. 



of tbe wiugs and straigbteuiug of the legs of tbe perfect insect, occupies 

 less than three quarters of an hour and sometimes but half an hour. It 

 takes place most frequently during the warmer hours of the morning, 

 and within an hour after the wings are once in position the parts have 

 become sufficiently dry and stiffened to enable the insect to move about 

 with ease, and hi another hour, with appetite sharpened by long fast, it 

 joins its voracious comrades and tries its new jaws. The molting period, 

 especially the last, is a very critical one, and during the helplessness 

 that belongs to it the unfortunate locust falls a prey to many enemies 

 which otherwise would not molest it, and not unfrequently to the 

 voracity of the more active individuals of its own species. — (Riley's 

 Eighth'Report.) 



The egg (Plate LXII, Fig. 1, c) is curved, cylindrical, .21 inch (5^ milli- 

 meters) in length, more pointed at the posterior than the anterior end. 

 The posterior end is. contracted just before the extreme tip, which is 

 smooth, the more or less regular pits which cover the chorion, or egg- 

 shell, being here obsolete. I have been unable to discover any micropyle, 

 or passage for the spermatozoa. The posterior end i^oints downward in 

 the egg-moss, so that the exit of the young locust from the anterior end 

 is thus rendered easier. Although I have not seen the larva actually 

 burst its way out of the egg, yet on the examination of between fifteen 

 and twenty deserted egg-shells, I have, without an exception, noticed in 

 them one, more usually two, slits extending from the head-end to the 

 middle of the egg. The egg-shell is without doubt burst open by the 

 puffing out or expansion of the membrane connecting the head and pro- 

 thorax, just as the common house-fly or flesh-fly bursts off" the end of 

 its pupa-case by the ijuffiug out of the front of the head. I have seen 

 the embryo make its exit in two or three instances. In one case I saw 

 a large jiiece of the egg-shell (chorion) fly off from in front of the face 

 while the face of the embryo piifled slightly out, and in another instance 

 the whole anterior end of the shell came off. In the locust I have ob- 

 served, as will be seen farther on, that the amnion is ruptured by the 

 forcible expansion of the membrane behind the head, the larv?e before 

 walking lying on their backs or sides and forcing this membrane out- 

 ward. This action probably begins before the shell is burst and seems 

 amply sufficient to burst the brittle chorion, which is easily broken and 

 peeled off by rubbing the egg between the fingers, leaving the serous 

 membrane beneath. The pressure thus exerted must be a lateral one, 

 and sufficient to rupture the chorion. 



In his ninth report on the injurious insects of Missouri, Professor liiley 

 maintains that besides " a continuation of undulating contractions and 

 expansions of the body," the tips of the jaws and " sharp tips of the 

 hind tibial spines," the shell is ruptured, and then " splits up to the 

 eyes or beyond, by the swelling of the head." I think the swelling of 

 the space between the head and thorax is sufiicient to accomplish the 

 rupture of the shell. It may be objected to Mr. Eiley's account of the 

 supposed action of the jaws and spines that, as may be seen by my Fig. 2, 

 the position of the legs is such that the tibial spines do not point out- 

 ward, the tibiae being placed between the femora, and the legs are not 

 displaced until after the amnion is shed. Moreover the spines are soft 

 and flabby, as well as the legs ; besides this the legs and the entire body 

 are covered by the amnion, the tibitB being smooth. Did the spines saw 

 through both the chorion and serous membrane, the amnion would, of 

 course, be ruptured. I also do not think that the jaws would be available 

 until after the amnion has been cast. That the jaws are not moved out of 

 their place until after the embryo leaves its egg-shell and throws off its 



