13 



( 3 ) The importation of parasites from one country to another. 



( I ) In the great majority of cases of insect outbreak the native par- 

 asites are able to control it in time. In fact injurious forms are mainly 

 held in check by their parasites. Occasionally however, through the opferar 

 lion of some obscure factor, the multiplication of parasites is prevented; 

 then the injurious forms are permitted to reproduce with much less check 

 and much loss occurs before parasites are able to "catch-up" again. Sev- 

 eral prominent entomologists have called attention to the need for taking 

 greater care of parasites. C. V. Riley urged that measures be taken to 

 permit the parasite of the Rascal Iveaf Crumpler and of the Bagworm to 

 escape from the winter nests. Comstock made a similar recom.menda- 

 tion with regard to the chrysalids of the imported cabbage wormi and 

 the Cotton Caterpillar. Decaux in Krance advised preserving apple buds 

 attacked by the Anthonomus weevil in boxes covered with gauze so as 

 to allow the parasites to escape. It is said that he carried out his plan 

 in 1880 \vitli great success. 



Several cases are on record w^here outbreaks have been successfully 

 treated by the use of beneficial insects. Boisgiraud of France in 1840 con- 

 trolled a plague of Gipsy caterpillars by placing among them the carabid 

 beetle, Calosoma sycophanta. 



( 2 ) Some successes have been reported where parasites were transport- 

 ed from one locality to another. LeBaron of Illinois in 1872 introduced 

 Aphelinus mali a parasite of the Oyster Shell Scale. Webster in 1907 

 transported Polygnotus hicmalis from Marion, Pa., to a field of wheat 

 infested with Hessian Fly at Sharpsburg, Md., and observed that later in 

 the season every 'flax-seed' was parasitized. W.D. Hiinter introduced para- 

 sites of the Cotton Boll Weevil from Waco to Dallas and from Texas to 

 Ivcuisiana with considerable success. 



( 3 ) Several conspicuous successes have attended the im.portation of 

 parasites from, foreign countries. Perhaps the introduction of (a) Novius 

 cardinalis from Australia to California in 1888 for the purpose of 

 controlling the Cottony Cushion or Fluted Scale of the Orange ( Icerya 

 purchasi ) is one of t^e most interesting cases. This scale was brought 

 to California about 1868, probably on Acacia latifolia. It began to mul- 

 tiply rapidly in the orange and] lemon groves in spite of every m.easure 

 that was tried against it. Riley, U. S. entomologist, and his staff made 

 the scale a subject of special study for four or five years and he became 

 convinced that it w^as a native of Australia. Accordingly, tw^o entomolo- 

 gists, Koebele and Webster, w^ere sent to that coimtry to collect possible 

 parasites, and to send them to California. Novius cardinalis w^as found 

 at Adelaide and small shipmients of it were sent. The I^ady-birds began 

 to feed on the Icerya scale insect as soon as they were liberated, and 

 to breed rapidly — the result being that within a year the orange growers 

 confessed that their groves had been saved. 



