HEMIPTERA-HOMOPTERA CHAP. 



after the discovery of America by the cochineal Insect, Coccus 

 cacti, a Mexican Coccid feeding on a Cactus called Nopal 

 (Opuntia coccinellifera). This Insect was subsequently introduced 

 to the Eastern hemisphere, and was established with more or 

 less success in a few spots on the borders of the Mediterranean. 

 In the Canary Islands it flourished on other species of Cactus-, 

 became acclimatised, and was the object of an extensive commerce. 

 The colour in the case of all these Coccid dyes was obtained from 

 the bodies of the Insects, in the tissues of which it is contained. 

 The dyes have now been largely displaced in commerce by the 

 derivatives of Aniline. Axin is produced by the Mexican Coccid 

 Llaveia axinus ; this substance appears to be of a very peculiar 

 nature ; it is apparently chiefly fatty, and contains a peculiar acid, 

 axinic acid. Axin is used as an external medicinal application 

 in various affections ; and it is also employed as a varnish ; it 

 dries and hardens on exposure to the air, and is said to be of 

 considerable value. 1 In our British genus Orthczia the body of 

 the female is completely covered with a symmetrical snow-white 

 armour, from which project the pink legs and antennae. This is 

 one of the forms in which the female preserves the legs to the 

 end of her life. The objects called ground-pearls, already alluded 

 to, have long been known in various parts of the world, and in 

 the island of St. Vincent they are sufficiently large to be collected 

 and strung for necklaces. These bodies are the encysted pupae 

 of Coccids of the genus Margarodes ; the cyst is said to be of 

 chitin. M. vitis commits serious ravages on the vines in Chili 

 by sucking their roots, and it is probable that all the species are 

 of subterranean habits ; this would partially explain the fact 

 that very little is known about the history of these pearls, 

 though naturalists have been acquainted with them for many 

 years. 



The gall-making Coccids of the group Brachyscelides have 

 only recently been at all investigated ; the galls they give rise 

 to are sometimes about a foot in length, and there appear to be 

 numerous species and several genera in Australia ; they are 

 especially abundant on Encalyirfvs and Acacias. The females are 

 highly remarkable from the variable conditions the legs assume, 

 so that in some cases they may be described as biped Insects, the 



1 For additional information as to useful Coccidae, see Blanchard, Bull. tioc. Zool. 

 France, viii. 1883, p. 217. 



