18 



Other Insects. 



This Coccus is not the only insect that 

 subsists on Opuntias in India.* 



An armoured scale insect, belonging to the 

 genus Diaspis, was observed occurring very 

 thickly on Opuntia nigricans near the Manri 

 State Farm, Poona district, and on varieties of 

 Opuntia decumana under cultivation at Dhond. 

 It was also met. with at Grundlupet, Southern 

 Mysore, on 0. dillenii throughout a rather large 

 area, and in some spots plentifully. The coecid 

 in all these occurrences seemed referable to a 

 single species. In no instance was a plant ob- 

 served to be destroyed or even checked to any 

 extent in its growth by it. 



However, Eam Rao S. Kasargode, Lecturer 

 in Entomology at the Poona Agricultural College, 

 stated that this plant-louse has been identified 

 by E. B. Green as Diaspis echinocacti, Bouche 

 and has been found in the Bombay Presidency 

 on Opuntia on both sides of the flat stems. 

 It is widely distributed, and occurs especially 

 during the months of March and April. It was 

 observed to be destructive in only one instance — 

 that of a hedge — in Ahmednagar district. 



A species of Diaspis f was found on a few 

 specimens of an Opuntia in the Calcutta Botanic 

 Gardens and on the " Punjab Pear" growing.in 

 the Lucknow Gardens, but it had no visible 

 detrimental effect. 



In the Brisbane district this, or an allied 

 species of cactus-loving Diaspis (referred to as 

 Diaspis calyptroides, Costa, var. Cacti, Com- 

 stock), occurs on Opuntia and other Cactaeege 

 so plentifully as almost to whiten the stem- joints. 

 Occasionally under experimental conditions it 

 has been foimd to kill badly-rooted individuals 

 of Opuntias inermis there (Tryon, 1911, p. 17). 



Two other insects injuriously associated with 

 Prickly-pear in Southern India, but not to the 

 extent of destroying it, were brought under notice 

 by T. Rainbridge Fletcher, Government Ento- 

 mologist, Agricultural College, Coimbatore, 

 Madras. They were: — 



A large Cantharid beetle named Mylabras 

 pustulata. This, it was stated, consumed 

 the flowers of Opuntia, but not so com- 

 monly, or in such a manner, as to affect 

 in any way its spread. The yellow 

 blooms of many other yellow-flowering 

 plants it was also partial to, and was 

 especially addicted to attacking Hibiscus 

 in this manner. It is related to an insect 

 that we have observed in Natal as harm- 

 ful to cultivated Leguminosas, by 

 similarly attacking their blossoms. 



An Erotylid Beetle (gen. et sp. undeterm.). 

 This was said to feed in the dead stem- 

 joints of Priekly-pears. Again, it was 

 an insect that was not an exclusive 

 enemy of Opuntia, being more partial 

 to EupTiorlia than to it. In this latter 

 plant it usually followed the injuries due 

 to Pyralid moths. 



* BurkiU (1911, p. 305) has given an account of the 

 unsuccessful attempts to introduce the trae cochineal 

 jnseot or grana fina into India. 



t Mrs. Femald, in her Catalogue of the Cocoida of the 

 world, mentions India as a locality for Diaspis echinocacti 

 Bouch6, as well as its subspecies cacti, Comstock ' 



B. Diseases. 



No disease of a parasitic nature capable of 

 destroying Prickly-pear was met with in 

 India. 



Moreover, no instance of a special pernieious 

 influence being exerted by any higher plant on it 

 was observed ; although, in travelling through the 

 Caveri Valley, it was noted that when Jatropa 

 and, Opuntia were associated in growth on the 

 same site the latter usually presented a depauper- 

 ated habit. 



Local conditions were at times, however, 

 decidedly prejudicial to it, and occasionally fatal. 

 The excessively moist climate of certain parts 

 of Assam and Bengal is detrimental to most 

 species, the only one able to withstand such con- 

 ditions being 0. monacoAitha, which, however, is 

 not a pest in any part of India, as far as is 

 recorded. 



The very hot, dry season experienced in 

 most parts of India during some part of the year 

 cheeks growth of most plant life, and even such 

 Prickly-pears as 0. dillenii and 0- nigricans 

 suffer, becoming drooped and chlorosed, many 

 dying, especially those growing in poor land on 

 hillsides or along hedges, the drainage in these 

 cases being such that little, if any, moisture 

 remains available in the soil for plant growth. 

 In a large area, of which Trichinopoly may be 

 regarded as about the centre, many clumps of 

 0. dillenii were observed where the growth of 

 individuals had evidently almost ceased, and their 

 surfaces had become brown and suberised — ^the 

 dead epidermis supporting various micro-fungi. 

 This state of things appears to coincide with 

 uncongenial conditions of growth, being especially 

 evinced where the plants were older and where 

 the soil was shallow and reposed on a stony or 

 otherwise unsuitable substratum. This gradual 

 local decadence of the Prickly-pear recalled a state 

 of things very noticeable within the town of Gayn- 

 dah and to a less pronounced extent elsewhere, 

 within the State of Queensland. 



In a memorandum (6th December, 1912), 

 prepared by Mr. R. C. Wood, Principal of the 

 Agricultural College and Research Institute, 

 Coimbatore, in view of the Commission's pro- 

 jected investigations, and addressed to the Con- 

 servator of Forests, Western Circle, it is stated 

 as follows: — "The Government Entomologist 

 and Government Mycologist report that, so far 

 as their knowledge goes, there is no insect nor 

 fungus in this country that is likely to prove 

 valuable in the destruction of Priekly-pear." 



Some years previous to this — in 1886— the 

 Madras Government requested the Superinten- 

 dent of the Madras Government Museum (Dr. E. 

 Thurston) "to institute an inquiry ... as 

 to the practicability of destroying Prickly-pear 

 {Opuntia dillenii) by means of Cochineal Insects 

 or other parasites," this officer reporting on 15th 

 June, 1896, as follows:—" No parasites, animal 

 or vegetable, have been ovserved living on 

 Prickly-pear in such a manner as to warrant a 

 hope that they might be used as an agency for 

 the destruction of the plants."* The Board 

 accordingly concludedt that " there are no 

 parasites known to the Presidency which can be 

 relied on to dest roy Prickly-pear growth." 



* Vid. Proceedings Board of Revenue, &c.. No. 135, 

 17th June, 1896. 



t Vid, I.e. Besolution No, 1. 



