408 BIOLOGICAL CONTROL 



its kind likely to be propagated much along the same lines as the 

 introduced predator Cryptolamus (p. 377). The largest scale 

 experiments are being conducted in Louisiana and California, with 

 reference to the control of the cane-borer and codling moth 

 respectively. According to S. E. Flanders the Trichogramma can 

 complete its life-cycle in eight days at a temperature of about 

 83° F. It is readily bred in captivity upon the eggs of the 

 Angoumois grain moth (Sitotroga cerealella Oliv.), which likewise 

 is capable of many generations in the year, and the whole technique 

 for the mass-rearing of the parasite on this host has become a 

 matter of skilfully standardised routine. With comparatively 

 simple and inexpensive technique it has been possible to rear 

 200,000 individual Trichogramma a day at certain periods, while 

 numbers approaching one million per day are stated to have been 

 attained subsequently. Whether the reduction of the host 

 population can be regularly attained to a degree which justifies 

 the expenditure of money on projects of this kind has given rise 

 to a good deal of doubt. While encouraging results are reported 

 by Tucker, in Barbados, on carefully analysed evidence, satis- 

 factory data are wanting elsewhere. The use of Trichogramma for 

 the purpose mentioned is, it may be added, inspiring less confidence 

 than formerly. 



Another experiment of this kind concerns the Coccinellid, 

 Hippodamia convergens, in California. This insect is generally 

 distributed in the areas involved by the experiment, but is 

 ineffective in controlling the great abundance of aphides on truck 

 crops, etc. It has been estimated that an increase of about 

 30,000 individuals per acre might be expected to give the result 

 desired. Watch was therefore kept in autumn in the canyons of 

 the Sierra Nevada Mountains where the Hippodamia congregate 

 in masses prior to hibernation, and the particular assembling 

 places marked. Before the snows melted in spring the hibernating 

 lady-birds were collected in enormous numbers and transferred 

 to storage plant in Sacramento, where they were retained at a 

 suitable temperature until required. 



On reports being received from farmers concerning aphid 

 outbreaks, shipments of the Coccinellids were made to the desired 



