liii 



large a percentage of these butterflies should have developed only to speed- 

 ily perish, shows, I think, the (as yet) imperfect adjustment of this insect 

 to the climate of its new habitat. It may be safely predicted that fewer 

 butterflies from the last brood will issue each successive year until they 

 finally cease to do so altogether. 



Many of the butterflies also came out during warm days in March this 

 year, and found no flowers yielding honey for their own nourishment, nor 

 any vegetation adapted to the needs of their progeny. They, consequently 

 must have perished before they were able to do any damage. Having 

 observed them carefully this spring, I am convinced that they will not ovi- 

 posit on any of our early wild cruciferous plants such as Cafsella, Lepi- 

 diutn, Arab/s, and the like. They are. however, speedily attracted to hot- 

 beds where young plants of cabbage, cauliflower, kohlrabi and allied species 

 are growing, and these demand careful attention to prevent loss. 



The Rape butterfly has already extended its range in this country from 

 far north into British America to the south of Georgia, and there is no 

 reason to doubt that it will be able to adapt itself to all the variations of 

 soil and climate incident to such a wide area. 



In Europe this pernicious insect is mainly kept in check by numerous 

 parasites, some of which attack it in one stage of development and some 

 in another. For several years after its advent into America none of these 

 natural allies came to the aid of the disheartened gardener who was obliged 

 to wage a single-handed warfare against it. After a few years several 

 parasitic insects were observed preying upon it in the districts in which it 

 first appeared. The most important of these parasites is a minute, metalic- 

 green Chalcis-fly {Pterotnalus puparium, Linn.), which is identical with 

 the most destructive European foe of P. rapce. This fly was at first sup- 

 posed to have followed the butterfly to this country —conveyed in infested 

 chrysalides, perhaps — but it has since been ascertained that it is indigen- 

 ous on both sides of the Atlantic, from the fact that it has been found in 

 localities where the Rape butterfly has not yet made its appearance. It 

 was probably originally parasitic on the larvae of the Northern Cabbage 

 butterfly (^Pieris oleracea),v^h.\c\\ closely resemble the European species. 



The fly places its eggs in or upon the skin of the mature caterpillar. 

 From these eggs proceed minute maggots, which subsist on the fatty tis- 

 sues of their victim, but do not touch its vital organs until after it changes 

 to chrysalis. Within the chrysalis shell they complete their transforma- 

 tions, the flies puncturing it in all parts when ready to emerge. 



As the Northern Cabbage butterfly does not occur with us, we are less 

 likely therefore to soon have the benefit of its parasite, unless, as might be 

 easily done, it is introduced in infested chrysalides. 



The artificial remedies consist of the application of hot water, whale oil 

 soapsuds, or strong tar-water, to the plants sufi"ering from the attacks of 

 the caterpillars. Paris green and some other poisons in the form of pow- 

 der will destroy the insects, but cannot be used with safety on vegetables 

 whose foliage or flowers ar^ used for food. 



