— 16 ~ 

 were mainly responsible for the reduction in numbers, but for the last five years 

 the webworms became scarce. The parasites died out and the birds became the 

 most important factor of control. Mr. Tothill pointed out that just when the 

 webworms were at the point of extinction a southeast wind brought in a flight of 

 webworm moths from Nova Scotia, with the result that these have greatly 

 increased since their parasites are few in number. 



He points out also that the 1917-1918 outbreak of Fall Webworms in Nova 

 Scotia was due to the scarcity of two parasites Varichaeta and Limnerium, which 

 were abundant in 1912- in New Brunswick, and that if measures had been taken 

 in 1912 to introduce these parasites into Nova Scotia, the outbreak could have 

 been prevented. 



Mr. Tothill also cites the case of a heavy isolated outbreak of Forest Cater- 

 pillars at Red Deer, Alberta, in 1917-18. An examination failed to find a single 

 parasite, and he believes that if precautions had been taken four years before to 

 introduce its two chief parasites, Limnerium and Blepharipeza, from the Atlantic 

 board or the Provinces where they were abundant, the outbreak could probably 

 have been prevented. 



Sphir.x cateri-illar with cocoons of braconid parasites. 



Australian ladybird-beetle (Novius cardinalis), 



the enemy of the cottony-cushion scale. 



(Natural size) 



a — lady bird larvae feeding on adult female 



and egg sac; b — pupa; c — adult ladybird; d — , 



orange twig, showing scales and ladybirds. 



<After Marlatt, I'nited States Dept. of Agric.) 



Elarly attempts to employ natural methods of control. 



Silvestri tells us that the first person to employ successfully parasitic and 

 predaceous insects was Boisgiraud of Poictiers, France. About 1840, he rid the 

 poplars along a promenade in a suburb of his town of the Gypsy moth by intro- 

 ducing the carabid Calosoma sycophanta, and he destroyed the forficulids in his 

 garden by using a rove beetle Staphylinus olcus. 



Boisgiraud's successes prompted a Milan Society in 1843 to offer a gold 

 m.edal to the person who had in the meantime carried out successfully experiments 

 on the artificial breeding of carnivorous insects which may be utilized to ad- 

 vantage for the destruction of other insects injurious to agriculture. Antonio 

 Villa responded with a report dealing with successful experiments he had carried 



