IO FIRST REPORT ON ECONOMIC BIOLOGY. 



been described in detail by Keux, 1 and later by Curtis; in spite of 

 this fact, however, we have made little progress in controlling- this 

 insect. Climatic conditions undoubtedly have much to do with its 

 increase. 



I have carefully studied experiments made on spraying the plants 

 and on soaking- the soil with different substances, but none have proved 

 successful. Clean cultivation and the destruction of all cruciferous 

 weeds must prove beneficial if generally carried out. 



These small beetles have considerable powers of flight, and 

 observation shows that they fly against the prevailing wind, 

 undoubtedly being attracted by the smell of the germinating seed. 

 Numerous experiments have been made to ward off the insects by a 

 counter odourant, but these, so far, have only proved partially success- 

 ful. Any experiments, to be of practical value, must be carried 

 out on a considerable acreage, and, as yet this has not been done. 

 Plot and garden experiments, in a case such as this, are useless to 

 the farmer. 



THE LARGE CABBAGE WHITE BUTTERFLY. 



Pieris brassicae, Linn. 



The years 1909 and 1910 were both characterized by a plague of 

 the Large Cabbage White Butterfly, that has not been equalled for 

 very many years back, in consequence of which, vegetable gardens 

 and small holdings suffered severely. 



The life-history is familiar to most people, but in view of the 

 recent plague it may be well to repeat it. 



LlFE-HlSTORY. 



The insects appear towards the end of April, and the females lay 

 their eggs in clusters usually on the underside of the leaves. In colour 

 they are lemon-yellow, cone-like, or sugar-loaf shaped, and marked by 

 fifteen to seventeen longitudinal ribs. The larvae hatch out in from 

 two to ten days, according to the season and temperature. 



The newly-hatched caterpillar is about 2 mm. long, and green 

 or brownish-green spotted with black; there are four moults, after 

 which they vary from a bluish-green to yellow, with black spots and 



1 Trans. Entom. Soc. Lond., vol. ii, p. 24. 



