294 NEW YORK STATE MUSEUM 



young of the San Jos6 scale are carried short distances by a strong wind, 

 and there is no reason why those of other species might not be conveyed 

 in the same manner. Evidence of one kind and another has been 

 accumulating to show that active young of the scale insects are carried 

 by other insects, birds and animals from tree to tree. It is also well 

 known that these forms are most readily transported long distances on 

 young trees and plants. This means is by far the most important, and 

 fortunately is the one most readily controlled. Methods of preventing 

 this dissemination will be considered under an appropriate head after the 

 discussion of several injurious forms. 



Certain species of value. Some Coccidae, or scale insects, are of 

 economic importance on account of their products. The well-known 

 cochineal is derived from the dried bodies of a scale insect, Coccus 

 cacti Linn., which, as is well known, lives on several species of Cac- 

 taceae in Mexico. Prof. Comstock states that this insect is also reared 

 in India, Spain and other countries. This species or a closely allied form 

 is found on wild cactus in Ceylon, as stated by Mr Green. -^ Another 

 species, Tachardia lacca Ker., excretes the substance from which 

 is made the "lac," or shellac, of commerce, and from the insect itself a 

 crimson pigment known as "lake" is obtained. This insect lives on 

 species of Fi c us and on C r o to n lacciferum. Prof. Comstock 

 has described two American species belonging to this genus, 

 Tachardia larreae and T. mexicana. The former occurs on 

 the creosote plant, Larrea mexicana, a plant growing in the south- 

 western part of the United States and in Mexico, and in Prof. Comstock "s 

 opinion this "lac" insect might prove of economic importance. The 

 latter species was found on a twig of mimosa from Tampico (Mex.) It 

 is interesting to record that Prof. Cockerell has subsequently described 

 four other American species of this genus. The waxy excretion of a 

 Chinese scale insect, Ericerus pela Westw. is used in the manufac- 

 ture of candles in that country. A near relative of our Gossyparia 

 ulmi Geoff., the Go ss yparia m an ni f era Hardw., " is found upon 

 Tamarix mannifera Ehr., a large tree growing upon Mt Sinai, the 

 young shoots of which are covered with the females, which, puncturing 

 them with their proboscis, cause them to discharge a great quantity of a 

 gummy secretion, which quickly hardens and drops from the tree, when 

 it is collected by the natives, who regard it a's the real manna of the 

 Israelites." ^ 



1 Green, E. E. Coccidae of Ceylon. 1S!I9. p. 3. 



2 West wood, J. O. Introduction to the moctern classlflcatlon of Insects. 2 :449. 



