22 CABBAGE. 



will be well ; but if, through drought, poor ground, or any 

 other cause, the caterpillars take more off than the plant 

 makes good, necessarily it gradually dwindles or perishes. 

 This point is a most important one to be considered in attacks 

 of this nature, and especially with regard to field crops, in 

 the case of which it is most difficult to employ any kind of 

 insect-jn-eventive in the shape of dressing, remuneratively. 



Severe cold in winter cannot be reckoned on as a means of 

 getting rid of the chrysalids, which is the state in which these 

 butterflies usually pass the winter. They have been found 

 attached to walls, and frozen so hard that they could be 

 snapped like sticks : yet those kept for observation appeared 

 perfectly healthy on Ijeing thawed, and produced butterflies in 

 due time. — (J. A. K.) 



During the severe winter of 1878-79, chrysalids of the 

 Cabbage Butterflies which I had opportunity of examining 

 appeared perfectly uninjured by cold, which ranged at various 

 temperatures between 10" and 30" on twenty-five nights in 

 January. The parasite maggots in a chrysalis of the Green- 

 veined White Butterfly were also only temporarily stifi'ened. 



The number of butterflies is much kept down by the various 

 kinds of small parasite flies which lay their eggs in the cater- 

 pillars or chrysalids, and especially by one kind of Ichneumon 

 Fly {Microgaster glomeratus), which lays sometimes more than 

 sixty eggs in one caterpillar of the "Large White." The 

 maggots from these eggs feed inside on all the parts not 

 necessary to the caterpillar's life till the time comes for it to 

 change to the chrysalis, when, instead of turning, it dies; the 

 Ichneumon maggots eat their way out and spin their little 

 yellow cocoons (like small silkworm cocoons) often seen on 

 Cabbages, from which a small four-wunged fly presently 

 appears. — (J, C.) These cocoons should not be destroyed. 



Another kind of Ichneumon Fly, the Pteromahis hrassicue, 

 figured above, lays its eggs on the chrysalis when it has just 

 cast its caterpillar-skin, and is soft and tender. The maggots, 

 averaging two hundred and fifty in number, eat their way 

 into the chrysalis as soon as they hatch, and feed on its 

 contents. 



Wasps also help to keep the butterflies in check, and have 

 been observed especially to attack the " Small White," or 

 Turnip Butterfly. 



Small White Cabbage Butterfly. Pieiis rapa, Linn. 



The caterpillar of this butterfly (known also as the Turnip 

 Butterfly) feeds on Cabbage, also on Turnip, from which it 

 takes its name of Turnip Butterfly ; and also on the inner 



