MIGRATION. 
419 
Terias is perhaps the most common of the Pierids, the little yellow 
butterflies with black edges to the wings which are so abundant through¬ 
out the plains. T. hecahe , Linn., has been reared upon Cassia tor a and 
probably feeds on several species of Cassia. Watson refers to it as having 
at least four broods yearly, and in favourable places possibly twelve. 
It has been reared in Bengal also on Jainta ( Seshania aculeata). 
The oval elongate egg is greenish white, laid singly on leaves. The 
larvaps green, with a lateral white stripe, and transverse wrinkles ; they 
pupate (after twenty days larval life) with the head downwards, the 
body in the girdle, and their colour is green or brown according to the 
leaves they are on or among. The pupal period varies from five days 
to twenty-five days. This species is variable in markings and is not 
easily distinguished from T. venata , Mo., T. libythea, F., and T. Iceta , 
Boisd., which also occur in the plains. 
Coleiis amata , Fabr. {Teracolus cyproea) is orange above, with many 
dull black markings, and yellowish below. The larva is striking, as it 
feeds in company on the leaves of Salvadora 
persica; the full grown larva is cylindrical, 
yellow green, the head and body with 
tubercles bearing hairs, at the end of each 
of which is a drop of fluid. These feed in 
a row, eating away the epidermis and 
gradually moving down the leaf. They are 
common where this plant grows in the drier parts of India. Coletis 
(Teracolus) etrida, Boisd., may also be expected in the plains. 
Fig. 290— Coletis amata. 
MIGRATION. 
To those who live in tropical countries, the migration of insects will 
suggest at once the flight of vast swarms of locusts, perceived as a cloud 
on the horizon growing larger as they approach till the sky is dark with 
them and they pass on overhead or alight for a while before resuming 
flight. In locusts we see the phenomenon in its most striking and 
exaggerated form, one in which the magnitude of the insects impresses 
us most distinctly and gives a perhaps exaggerated idea of tile actual 
numbers of insects concerned. 
We have in the Bombay Locust ( Acridium succinctum, Linn.) a most 
striking example of an insect that is at once an ordinary non-migrating 
