624 PROCEEDINGS OF THE THIRD ENTOMOLOGICAL MEETING 



the caterpillar feeds on a weed called " Agra " {Xanthium strumarium). 

 In order to see the efEect of the destruction of the weed on the first brood 

 of caterpillars, the whole area in question at Ghogha was completely 

 freed from the weed in 1917-18. But the result of the experiment was 

 not satisfactory. The first-brood caterpillars were found, in the absence 

 of the weed, on tobacco, kidtJii, etc., on higher lands surrounding the, 

 area. Destruction of the weed food-plant does not therefore appear to 

 have any chance of keeping the pest under control. 



(V) By Parasites. Under field conditions the caterpillar has several 

 parasites of which two Braconids are more in evidence than the Tachinids 

 of which there are more than one. Of the Braconids again one is more 

 numerous than the other. These parasites are first observed in the 

 field in October when the percentage of parasitization is very low but this 

 however gradually increases towards the end of the season. Ordinarily 

 it becomes 30 per cent, on an average by the end of December but in 1918 

 it was 74 per cent, in one plot at Ghogha. With a view to finding out 

 the possibilities of the parasite against Agrotis attack in the chaur land, 

 its life-history was completely worked out in the Insectary at Sabour 

 in 1917-18. The idea was that if a large number of adult para.sites could 

 be liberated in the normally attacked area early in the season, they would 

 by attacking the first brood caterpillar make the second or the destruc- 

 tive brood negligible. As regards its life-history, it has been found out 

 in the Insectary that in January to February the length of its egg and 

 larval stages is 25 days and the pupal stage is 11 days — total 36 days. 

 In March the periods are 17 days and 8 days respectively — total 25 days. 

 In April the length of the egg and larval stages is 12 days on]}^ It goes 

 into sestivation in March or April and remains as a grub inside the cocoon. 

 What is still unknown about its life cycle is the time when it comes out 

 of its aestivation in the chaur land. Presumably it does so along with the 

 appearance of the first brood caterpillars in the chaur in September or 

 October, when, its numbers being very small, on account of the exigencies 

 of climate and adverse chaur conditions during the aestivating period, 

 the percentage of parasitization is very low. With the idea of giving it a 

 fair start against the first brood in the beginning of the season, by in- 

 creasing their number, large broods of the parasite were reared in the 

 insectary in February and March 1917 and allowed to go into aestivation 

 in April. The grubs inside remained healthy through the summer and 

 the rains and even in the first week of October they were alive, but they 

 failed to pupate and come out as adults. The same experiment was 

 repeated in the Insectary in 1918 with no better results. It is evident 

 that the natural factors controlling their emergence from the sestivating 

 pupae did not obtain in the Insectary. As it is not definitely known 



