148 Indian Museum Notes. [Vol. V. 



Habitat •' Europe and throughout India and Ceylon. Expanse 

 42 — 48 millim." [ 1*5 to i'g inches, but often the moths hardly reach 

 half this size.] The larva is known to be destructive to a great 

 variety of plants, especially to turnips and corn in Europe; in South 

 India and Ceylon it has been reported to eat the leaves of coffee, 

 vide " Indian Museum Notes," vol. iv, n. 2, p. 42, n. 9 (1897). 



Much has to be discovered as regards the lifehistory of this 

 destructive moth in India, especially as to its relation to the indigo 

 plant. For instance, when are the eggs laid that produce the young 

 larvse which eat off the young indigo when at its most vulnerable 

 stage, i.e., in the two, four, and seven leaf stages? Probably the 

 eggs are laid immediately the ycung leaves of the plant show them- 

 selves above the ground, and hatch in a very few days, three or four 

 perhaps. Again, why should the caterpillars do such great damage 

 in some years, and be comparatively innocuous in others ? Why 

 should the moist east winds be favourable and the dry west winds be 

 unfavourable for their development? It might be suggested that 

 with a moist atmosphere the plant is more succulent and therefore 

 affords better pabulum for the minute caterpillar when first hatched 

 than the plants would be under a dry and burning west wind, which 

 would render the leaves tough and leathery. Again, what becomes of 

 the insects when the indigo is safe, i.e., past the seven-leaf stage, 

 till the next season comes round ? I may note here that later on in 

 the year when I collected thousands of caterpillars embracing many 

 species in the mature indigo, I did not meet with a single larva of 

 A. segetis, though 1901 being a bad year for the insect they may 

 have been present in the indigo, but in few numbers, and so escaped 

 observation. Or the insect may, and probably does, feed on many 

 other plants besides indigo, and so is enabled to carry on the species 

 from one season to the next by this means. It is found in August, 

 however, as I obtained two very small specimens at Seeraha at night. 

 Another question that puzzles indigo planters greatly with regard 

 to this insect is a reason for its being so much more prevalent on 

 seeted lands (i.e., lands highly manured with the refuse plants from 

 the indigo fermenting vats after the indigo has been extracted) 

 than on lands not so manured. The only reason I can suggest is 

 that plants from manured land are naturally the most vigorous, and 

 consequently can bear a larger "crop" of caterpillars than poor 

 indigo from worn-out, unmanured lands. The eggs are certainly 

 not laid in the seet as has been suggested. 



On May 28th, 1901, a letter headed " The Caterpillar Pest " 

 appeared in The Englishman, from which the following extracts 



