THE LOCUSTS OF THE OLD WORLD. 469 



On its emergence tbe larva is yellowish-white, with a rosy tinge; in 

 three to four hours its color is grayish-black. Before and during each 

 moult the larva3 are sluggish. At the final moult, which always takes 

 place in the hottest sunshine, the animals hang head downward, by the 

 hind feet, upon the stalks of grasses, &c. This enables the insects to 

 twist about in all directions, in order to free themselves from the skin. 

 The expansion of the wings occupies about twenty minutes after the 

 completion of the moult (twenty-two minutes according to Koste, who 

 says that the moult itself occupies sixteen minutes) ; during this period 

 Koppen observed that a dark yellow fluid was distributed over the 

 wings in microscopic drops. The period which elapsed between the 

 arrival of the insect at the winged state and the deposition of the eggs 

 is uncertain j the statements of different authors vary between four 

 weeks and two months. 



Koppen describes the nearly indiscriminate voracity of these insects, 

 but remarks that certain plants appear to be avoided by them, namely, 

 flax and hemp, the Cucurhitacece, and, according to Petzholdt, dwarf 

 garden-beans. The Graminece seem to furnish their favorite food. They 

 prefer the leaves and other soft parts of plants and trees, but also some- 

 times gnaw the bark and even the wood of the latter. In time of scar- 

 city the}^ will attack straw-thatch and woolen clothes, and even devour 

 each other. Koppen notices the statement made by various authors 

 that the larvae for the first ten days live upon dew, and treats it as an 

 absurdity. 



The perfect insects copulate almost immediately after the last change 

 of skin. The union of the sexes continues apparently for a consider- 

 able time, from twelve to eighteen or even twenty-four hours, but some- 

 times only for an hour or two. The female carries the male about with 

 her, and feeds as if alone ; she is, however, unable to fly. The male sits 

 quite motionless, only giving a sign of life by stridulation if another 

 male should approach. 



The eggs are deposited about seven days after copulation, according 

 to Koste. The female digs a hole in the earth of about li inches, by 

 means of the hook-like horny organs of the apex of the abdomen, and 

 the eggs are then laid in cylindrical masses, usually placed at an angle 

 of about 450 to the surface. The eggs are united by a spongy mass 

 (cement), which also envelopes the whole outside of the mass; here, by 

 the adhesion of grains of sand, small stones, &c., it forms a sort of wall 

 which protects the eggs from injurious external influences. The mass 

 is sometimes formed wholly or partially of the frothy cement without 

 eggs. Yersin ascribes this to a morbid condition of the female, and 

 doubts whether the few eggs contained in such masses are capable of 

 development. Koppen has found, on removing the female insect, that 

 the pit which it had dug was filled with the frothy mass without any 

 eggs. This seems to the recorder to indicate rather that the cement 

 mass is first produced by the insect, and the eggs afterward laid in it. 



