•2tG JOURNAL, BOMBAY NATURAL HISTORY SOCIETY. 1891. 



locusts take from about three weeks to two months to become full-grown and to 

 acquire wings, the length of the time spent as eggs and wingless larvae appearing 

 to depend chiefly on the temperature and moisture, cold retarding and heat acce- 

 lerating the devlopement* When first hatched the young locusts are grass green 

 in colour and quite helpless, but they speedily become almost entirely black in 

 colour, and are then able to hop about five or six inches at a time and begin to 

 feed ; after this they change their skins at intervals and grow, becoming more 

 vellowish in colour after each molt. Imperfect wings appear during the last two 

 stages of larval life, and the insect creeps out of its last larval skin with salmon- 

 pink body and fully developed mottled wings, which serve for flight as soon as 

 thev are dry. The change from green to black, which takes place a few hours 

 after the larval escape from the eggs, is no doubt due to the molting of the green 

 skin, but this change takes place so rapidly that the actual molting of the skin 

 has not been observed. t After this, two molts take place before the insect 

 changes its skin for the last time, to emerge as a winged locust, so that altogether 

 the insect molts its skin four times. After acquiring wings the young locusts soon 

 take wing and form the flights which travel about the country, sometimes for 

 months, alighting at intervals to feed upon the crops, until the time comes, either 

 to oviposit, or else to die off owing to the inhospitable nature of the areas into 

 which they have penetrated. As they get older the colour of the winged insects 

 changes from pink to yellow — a transformation which in Algeria has been sup- 

 posed to mark the sexual maturity of the insect, though from what has been 

 observed in India there would seem to be some doubt about this point. 



As far as the present information goes therefore, it seems likely that the life- 

 history of Acridium peregrinum in India is shortly as 



Summary of the life follows. But it should be borne in mind that several 



of the points, especially in connection with the parent- 

 age of the second generation, are not definitely established, and may prove to be 

 erroneous. Permanent breeding-grounds lie in the sand-hills of Western Rajputana 

 and in the Suliman Range. Here the flights remain comparatively inactive 



* In the spriug of 1890, eggs both in Rawalpindi and in Shikarpur took about three 

 weeks to hatch. Larvae reared in Rawalpindi took about eight weeks to develop, 

 while larvae from Shikarpur eggs, reared in Calcutta, became full-grown in a month, 

 a marked acceleration in development occurring after they had been supplied with 

 water. In Hissar, in 1889, eggs were said to have hatched in fifteen days, and the 

 young locusts to have acquired wings three weeks after hatching out. 



t The shortness of the period passed by the insect in this stage, combined with 

 the fact that its surroundings are the same when it is green as when it is almost 

 black, would seem to indicate that the green stage is a survival, probably presenting 

 the predominant coloration of the ancestral form, and hence indicating that this 

 desert species is descended from some inhabitant of more fertile lands where green 

 foloration would be as advantageous in rendering it inconspicuous amongst foliage 

 as its present black coloration no doubt is in the desert, where the birds are likely to 

 mistake it for the black sha low of a pebble upon the sand. 



