198 Memoirs of the Caledonian Horticultural Society, 



caterpillar state ; and found that water, heated to 140" Fahr., 

 and thrown forcibly upon them through the rose of a water- 

 ing-pot, kills them, and 'without injuring the tenderest leaves 

 on the bushes. But care must be taken to have the water 

 nearly at that temperature ; as, if five degrees lower, it will 

 scarcely kill the larvae ; and, if more than five higher, it will 

 injure the bushes ; so nearly does the vitality of the cater- 

 pillar coincide with that of the leaf on which it feeds. 



" But water thrown upon them in this way even as low as 

 120° makes them drop instantly from the bush ; and I would 

 therefore recommend to beginners to use the water at this 

 temperature ; a cloth being spread under the bush, to collect 

 them for destruction, as afterwards mentioned. 



"Of all the other things that I have seen recommended, and 

 many more that I have tried, none kills the caterpillar without 

 injuring the bushes. Here, as usual, the simplest of all agents 

 is the most powerful. 



" From a great variety of experiments, I found that the 

 duration of life of the insect varied considerably, according to 

 circumstances, in all its stages, except in the fly state, which 

 appears to be uniformly from nine to eleven days. In this 

 state it seems to take no food. It generally lays most of its 

 ova on the second, third, and fourth days, but sometimes 

 continues to lay a few till the seventh or eighth day. Under 

 the most favourable circumstances the ova are hatched in 

 seven days ; the life of the caterpillar is fifteen days, of the 

 pupa eighteen days. In the most favourable weather for that 

 purpose, therefore, a new generation is produced every forty- 

 two days, namely, four days for the fly to lay its eggs, seven 

 days for these to hatch, fourteen days in the caterpillar, and 

 seventeen in the pupa state ; and, as the first flies for the 

 season generally come up about the beginning of April, and 

 continue to come up, if the weather is fine, as late as the end 

 of October, there may be five distinct generations in one sea- 

 son. They are, however, subject to many incidents, and 

 therefore seldom more than two generations, of any consider- 

 able extent, appear in one season. 



"They are generally said to be extremely voracious, but this 

 is owing to their great nvimbers ; for, upon an average, each 

 caterpillar barely eats one leaf during its whole life, the female 

 eating more than double of what the male eats. For the first 

 five or six days they eat very little, each at that time having 

 made only a small hole in the leaf, of about one tenth of an 

 inch in diameter. It is in the last four or five days that they 

 make the havoc on the bushes ; and the damage is therefore 

 nearly all done before it is discovered. Those who look pro- 



