PREVIOUS WORK WI^H INSECT PARASITES. 19 



Insects of Missouri, 1 he advocated the collecting of the winter cases of 

 the destructive insect and placing the cases in small vessels in the 

 center of a meadow or field, away from any fruit trees, with the idea 

 that the worms would be able to wander only a few yards and would 

 perish from exhaustion or starvation, while their parasites would 

 escape and fly back to the fruit trees. It is stated that this method 

 was put in practice later by D. B. Wier with success. 



A French writer, F. Decaux, the following year made practically 

 the same suggestion with regard to apple buds attacked by Anthono- 

 mus. He advised that instead of burning these buds, as was gener- 

 ally done, they be preserved in boxes covered with gauze, raising the 

 latter from time to time during the period of issuing of parasites so as 

 to permit them to escape. In 1880 he put this method in practice, 

 and collected in Picardy buds reddened by the Anthonomus from 

 800 apple trees, and thus accomplished the destruction of more than 

 1,000,000 individuals of the Anthonomus, setting at liberty about 

 250,000 parasites which aided the following year in the destruction of 

 the weevils. The following year the same process was repeated, and, 

 the orchards being isolated in the middle of cultivated fields, all serious 

 damage from the Anthonomus was stated to have been stopped for 

 10 years. 2 



Practically the same suggestion was made later, in 1877, by J. H. 

 Comstock, in regard to the imported cabbage worm (Pontia rapse L.). 

 Comstock deprecated the indiscriminate crushing of the chrysalids 

 collected under trap boards, on account of the large percentage which 

 contained parasites. He recommended instead the collecting of the 

 chrysalids and placing them in a box covered with a wire screen which 

 should permit the parasites to escape and at the same time confine the 

 butterflies so that they could be easily destroyed. The same author, 

 in his report upon cotton insects, 3 recommended a similar course with 

 the pupse of the cotton caterpillar (Alabama argillacea Hubn.). 



Riley later recommended the same plan for the bagworm ( Thyridop- 

 teryx ephemerxformis Haw.) ; Berlese in Italy recommended it for the 

 grapevine Cochylis, and Silvestri for the olive fly (Dacus olese Rossi), 

 for Prays oleellus Fab., and for AspJiondylia lupini Silv. 



Writing on the Hessian fly, Marchal has pointed out that the 

 destruction of the stubble remaining in the field after harvest may 

 have unfortunate consequences, for if this is done a little late there is 

 a risk that all of the destructive flies will have emerged and aban- 

 doned the stubble, exposing to destruction only the parasites whose 

 part would have been to stop the invasion the following year. Mar- 

 chal also points out that Kieffer has shown that one of the measures 



1 Riley, C. V. Fourth Report on the Insects of Missouri, p. 40, 1871. 



2 An excellent article covering these general questions was published by Decaux in the Journal of the 

 National Horticultural Society of France, vol. 22, pp. 158-184, 1899. 



8 Cotton Insects, pp. 230-231, Washington, 1879. 



