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HINTS ON REARING BOMBYX RUB I. 

 BY JOHN E. ROBSON, F.E.S. 



A difficulty has always been expeinenced in rearing Boinbyx rubi 

 from its earlier stages, because the larvse, which are full fed in 

 autumn, cannot then be induced to pupate, and can only be hibernated 

 by a very full exposure to the changes of the weather. This may 

 appear a simple matter, but it does not prove so easy of accomplish- 

 ment, for, besides exposure to the severity of the winter, they also 

 require to experience the more genial effects of the direct rays of the 

 sun in spring. To combine these, yet to confine the larvae, generally 

 proves so difficult that very few ever reach the pupal state. 



On our sandhills, where the larvae swarm in autumn, they retire 

 below the surface when full-fed, and, remaining there during the more 

 severe weather, emerge in spring to bask in the rays of the morning 

 sun, retiring again after mid-day as it declines. They do not go far 

 down, and are always susceptible to warmth after the new year. I 

 once noticed them out so early as January 10th, but that is quite an 

 exceptional date, as the day was unusually warm for the time of year. 

 Generally speaking March is well in before they appear in any num- 

 bers, but any really warm day may bring them out. 



I have had occasion to cross a portion of our sandhills at least 

 twice a week during the greater part of this year. This has given me 

 an opportunity of observing them in their natural habitat, and also of 

 obtaining a large number to rear at home. I saw them first on 

 February lOth ; it was exceptionally fine for the time of year, with a 

 west wind and hot sun. I picked up about 50 as I crossed— a walk of 

 about half a mile. I could easily have obtained very many more by 

 w^alking to and fro. On the 13th, an equally warm day, they were 

 just as numerous, and I took 20 or 30 more. 



I had found long ago, that when a number of them were enclosed 

 in a breeding cage with moss to spin in, one disturbed another and 

 prevented them making their cocoons, only a small proportion reaching 

 maturity. To prevent this I had placed each larva in a separate chip 

 box {\\ oz. size). In these they spun up readily, but there was always 

 a proportion of circular cocoons, in which the larva had not length to 

 straighten itself out before pupating, resulting in a crippled pupa 

 that never produced an imago. Attributing it to the shape of the box, 

 I now enclosed each in a separate paper box two inches square. These 

 were numbered and dated and placed on the shelf over the kitchen 

 fire. Most of the earliest batch had spun their cocoons by the 14th, 

 and by February 20th they all had done so. 



