THE NATUEAL ENEMIES OF THE CITRUS SCALE INSECTS. 



The natural predaceous enemies of scale insects of greatest impor- 

 tance are various species of ladybirds, as illustrated by the Australian 

 ladybirds (figs. 21 and 29) imported to control the fluted and black 

 scales, and a great many native species, which are very effective agents 

 in the control of these and other scale pests. The work of ladybirds 

 is especially important against the young of the armored scale and 

 against the softer and freely moving scale insects which secrete no 

 protective covering. Whenever, therefore, ladj'birds of any species 

 are found to be abundant on scale-covered trees, the}^ may be safely 

 recognized as friends and working in the interest of the grower. If 

 thej are very abundant, it may even be unwise to fumigate or spray. 

 The black scale has been completely controlled on certain ranches in 

 California by its imported ladybird enemy, and this control has been 

 brought about by the entire cessation of all insecticide operations. 

 Most of our ladj^birds, however, will probably stand a spraying with- 

 out being killed, and, as a rule, it is hardly worth while to take the 

 risk of loss while waiting for them to do their work. The experience, 

 however, on the Cooper ranch and in other localities in California 

 has certainl}'^ demonstrated the advantage of giving natural enemies 

 a fair chance. 



The other important class of enemies of scale insects are the hymen- 

 opterous parasites. The recognition of these is not so easy, but if 

 scales are found pierced with minute round holes, it is a safe indication 

 that they have been parasitized, and that the parasites have escaped 

 and are multiplying in the younger scale insects on the trees, and here 

 again if the parasitism is found to be general, it may be inadvisable to 

 spray or fumigate. 



The other natural enemies of scale insects are not so important as 

 those mentioned; still the}'^ are of service, and should be recognized. 

 These include the larvaB of the lace-winged flies ( Chrysapa spp.), which 

 feed on the young of both the armored and the unarmored scales. 

 There are also a few dipterous, or fl}', parasites of scale insects, and the 

 larva3 of several species of Lepidoptera are carnivorous and feed on the 

 larger species of scale insects, such as the Lecaniums and wax scales. 



A most desirable outcome would be to secure a complete and prac- 

 tical control of scale insects b}'- their natural enemies; but, so far, this 

 has been fully accomplished in the case of the fluted scale only. Very 

 encouraging results have been secured, however, with other parasites, 

 and the introduction of these is being actively prosecuted. Neverthe- 

 less, spraying and fumigation must be relied upon for some time to 

 come, or at least until the natural enemies have been more fully studied 

 and better means of successfully colonizing them devised. Climatic 

 conditions also affect the activity of these enemies to such an extent 

 that the same results may not be counted on in different localities. 



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