46 REPORT ON THE DISEASES OF SILKWORMS IN INDIA 



to the roof but leaving a space of a foot- and-a- half or two feet between 

 the top of the wall and the slope of the roof. This could be covered 

 with gauze, the roof of course being supported by pillars or posts 

 running up above the top of the wall. As these openings would be 

 protected by the eaves they would not be exposed to the force of the 

 dust-bearing wind, but if it was thought necessary light shutters 

 could be provided to close when necessary. In French Indo-China 

 it was found that rearing houses constructed on the European plan 

 — pukk% houses in fact— failed signally, while houses on the 

 native plan succeeded admirably (Vieil, 1906). It would be folly 

 after the attempts made in Indo-China — and there were several-^ 

 to introduce that type of house into India. The only thing to be 

 advanced in their favour is that they are more easily disinfected 

 and kept clean than hutcha houses, but as these are not the hot- 

 beds of infection they were thought to be, that argument is not of 

 much worth. 



While it is undoubtedly possible to improve the circulation of air 

 in the rearing houses in the Government nurseries, it is a very differ- 

 ent question in the rearers' houses. When new houses are being 

 built under the supervision of a sericultural department the matter 

 is simple, and more air and light could easily be obtained as has been 

 above indicated ; but in the houses already erected, especially when 

 they are also used as dwelling houses, probably very little can be 

 done. However, the question of improved ventilation is one which 

 should always be in the forefront of the programme of any 

 sericultural department and it is one which can best be decided 

 locally. 



The darkness of the houses is also to be deprecated. It is said 

 that on account of the fly the houses must be kept dark, but it is 

 quite likely that the eye has little to do with the finding of the 

 caterpillar by the fly and the laying on it of the egg. Before the fly 

 could possibly see the worms — while the fly is outside and the worm 

 inside a house — the fly can find out the worm. It must do this by 

 some sense other than sight, so that even in a dark house the 

 worms might not escape. Light in moderation is certainly not 

 harmful to caterpillars, and a beginning should be made in the 

 Government buildings, at least, to dispel the tomb-like blackness 

 of the rearing houses. 



In connection with the subject of ventilation it may be noted 

 that it seems to be moisture in the air that is most to be dreaded. 

 As will be seen from Experiments 16 and 17, when caterpillars were 

 reared in a very moist atmosphere they were much more liable 

 to disease than when the air was dry, although in the moist cages the 

 -caterpillars grew much faster and larger than in the dry ones and 



