DactylopiincB. 359 



dillenicB is exempt from attack in India, and Tryon found the same condition 

 in Ceylon {vide Report of the Prickly Pear Travelling Commission, Queensland 



1914)- 



Plants that are thickly infested by the insect have an unhealthy appearance 

 that is noticeable from a considerable distance. It appears indeed, from Tryon's 

 researches, that ' O. monocantha was formerly abundant in India and Ceylon, 

 but has been practically exterminated there by the action of a wild Cochineal 

 Insect {Coccus indicus)' Its place has now been occupied (in Ceylon) by the 

 immune species Opuntia dillenia:. 



A similar action has been observed in South Africa, where Lounsbury 

 remarks — in his Annual Report for 1915-16 — that 'the Indian Cochineal Insect 

 is eradicating with astonishing rapidity the Monacantha prickly pear, especially 

 in Natal.' A small colony of Z>. indicus was taken to South Africa in 1913 by 

 the Queensland Prickly Pear Commission, and — according to the Report — 

 'already nothing but a few dried stumps remain where there were formerly 

 veritable walls of this plant.' It is remarkable that the African Cochineal 

 Insect {D. confusus-capensis), though so closely allied to D. indicus, has in- 

 fested the same species of prickly pear in South Africa for nearly a hundred 

 years without any injurious effect. This idiosyncrasy of the Indian insect makes 

 it a very valuable ally in the extermination of Opuntia monocantha in countries 

 where that noxious weed has overrun what would otherwise be useful pasture 

 land. 



The origin of the wild Cochineal Insect, in India and Ceylon, is obscure. 

 Burkill {Record of the Botanical Society of India, Vol. IV. No. 6, 191 1) 

 quotes evidence to show that the insect was introduced into India in 1795, ^i^d 

 Tryon {Queenslafid Agricultural Jourtt.,Yo\.yiX.Y . Part 4, Oct. 1910) gives 

 Brazil as the source of this introduction. There were apparently subsequent 

 introductions in 1821 and somewhere about 1840, and again in 1883 — when the 

 Government of Madras imported the insect from Algiers. Some of these intro- 

 ductions were undoubtedly of the cultivated Cochineal, though others are 

 definitely described as 'Wild' or 'Sylvestre' Cochineal. But whatever its 

 source, the fact remains that the form now found in India and Ceylon differs 

 markedly from any of the species or forms now existent in other countries, with 

 the possible exception of Dactylopius argentinus, from Argentina — the only 

 species that I have been unable to examine. 



Genus HALIMOCOCCUS, CklL 

 Halimococcus, CklL, The Entomologist, Vol. XXXV. p. 15, 1902. 

 (Plate CXLI.) 



Cockerell defines the genus {loc. cit.) as follows : ' A Dactylopiine Coccid 

 enclosed in a horny sac shaped like that of Solenococcus {Cerococcus), without 

 legs or antennas in the adult. Larva with no rows of dorsal spines, no hairs 

 on anal ring, and no caudal tubercles, but four long caudal bristles as in 



