296 INSECTS AND MAN 



of a rove beetle, Staphylinus sp., and a ground beetle, 

 Carabus auratus. 



The next efforts in this direction were carried out both 

 in Europe and America, and consisted in collecting large 

 numbers of destructive insects, many of them probably 

 smitten by internal parasites, and keeping them in cages 

 covered with fine wire-netting of such a mesh that the 

 adult injurious insects were unable to escape; but their 

 parasites, on reaching maturity, would have no difficulty in 

 gaining their freedom and thereby parasitising other hosts. 

 This method was tried in America with the imported 

 cabbage worm Pontia rapce and the cotton caterpillar 

 Alabama argillacea, and in Italy with the olive fly Dacus 

 olece, among others. 



A further stage in this important branch of economic 

 entomology appears to have been the transportation of 

 beneficial insects from one part of a country, where they 

 were plentiful, to another part of the same country, where 

 they were lacking. This method of natural insect control 

 has been successfully carried out in America, a striking- 

 case being that of the destructive Hessian fly, Cecidomyia 

 destructor, and its hymenopterous parasite, Polygnotus 

 hiemalis. In 1906 a serious outbreak of this fly occurred 

 in Pennsylvania, but was kept in hand because quite ninety 

 per cent, of the pupae were found to be parasitised by 

 Polygnotus. At a later date the Hessian fly pest broke 

 out in Maryland, and, in 1907, parasitised pupae were 

 brought from Pennsylvania, with the result that by mid- 

 summer all the fly pupae were discovered to be parasitised 

 and the pest was effectually controlled. 



Quite recently various species of ladybirds have been 

 collected in California, during their winter hibernation, for 

 shipment to various parts as a control for plant lice. As an 

 illustration of the magnitude of the undertaking, Mr E. K. 

 Carnes, who was in charge of the work, wrote, in 1910: 

 " We have quite a sight at the insectary now over a ton 



