THE FOOD PLANTS OF SCALE INSECTS (COCCID^). 



By T. D. A, COCKEEBLL. 



Euloviolos^isf of (he Nerv Mexico Affricnltural Experiment Staiiou. 



Int)-o(luctio)i. — It is not j)reteiuled that the following summary is 

 complete; to make it so would involve a much more elaborate search 

 through the scattered literatiire than the writer has now opportunity 

 for; and even then, a few months would inevitably bring new records, 

 and miike it incomplete again. It is, however, hoped that the sum- 

 mary will be of service, as bringing together the great majority of the 

 records, and indicating to the horticulturist what scale insects he may 

 expect to find on any given i)lant or group of plants. While it can not 

 be regarded as valid negative evidence, it presents a large mass of tixcts 

 which are of great importance from several points of view. Two prac- 

 tical points may be emphasized — one, the unexpected number of coccids 

 found on many of the cultivated trees and shrubs; and the other, the 

 frequency with which species dangerous to iruit trees will occur on 

 ornamental plants, which may be carried from place to place and be 

 the means of disseminating the scales. 



In preparing the summary, it has been found in many cases neces- 

 sary to correct the names of the plants given by writers on Coccidii?. 

 It is much to be desired that entomologists should be more careful to 

 correctly cite the names of plants they have occasion to mention. 



A card catalogue of host plants of Coccida^ is in preparation, and 

 may be seen at the United States Department of Agriculture. It may 

 be possible some day to complete it and publish a second and com- 

 plete edition of the present essay. Such a second edition would be 

 much larger than the present, for not only would it contain all the 

 scattered records of the past, but very numerous additions, which will 

 be found in Green's forthcoming monograph of the Coccida^ of Ceylon, 

 and other works projected or in preparation. 



It must of course be understood that the plants given as the hosts 

 of Coccida^ have been in very many cases so infested only since they 

 came into cultivation. It would be very desirable to distinguish in 

 every case between the endogenetic and exogenetic coccids on a i)lant; 

 and also between those exogenetic in a state of nature, and those only 

 so in cultivation. But to do this would require more information than 

 we at present possess. 



PROCtEDiNGS U. S. National Museum, Vol. XIX— No. 1122 



