85 



Certain rodents, especially species of 

 Neotoma, are capable of doing a great deal of 

 damage to and not infrequently destroy prickly- 

 pear plants, but their dietary is not restricted 

 to the Cactacese. 



In regard to the action of insects as 

 destroyers of prickly-pears, a large amount of 

 evidence has been collected. The most destruc- 

 tive are the beetles Moneilema spp., CoenopcBus 

 palmeri, and Gerstmclceria spp.; the moths 

 Melitara spp., and Mimorista flavidissimalis ; the 

 hemiptera Chelinidea spp., and Narnia spp. ; and 

 the diptera Asphondylia spp., and Itonida 

 opuntice. All of these are stated to be restricted 

 to the Cactacese. 



The larva of Moneilema forms tunnels in the 

 joints, stems, and roots, while the adult feeds 

 on the young segments. Ccenopceus acts similarly. 

 The cactus weevils, Gerstmckeria spp., occasion 

 more or less damage in the larval stage, the in- 

 juries caused by the adult being unimportant. 

 The larv£e live within the joints. 



The species of Melitara are the most destruc- 

 tive of the natural enemies of the prickly-pear, 

 the larvffi hollowing out the joints and sometimes 

 even the stems and roots, totally destroying the 

 plant. They are assisted by the larvte of scaveng- 

 ing flies and by invading micro-organisms. 



Mimorista commonly causes the destruction 

 of young segments and is therefore a powerful 

 factor in controlling the spread of prickly-pear. 



The bugs Narnia and Chelinidea attack the 

 fruit and stem- joints respectively and are said 

 to be at times a serious menace to the health of 

 the host plant. It is also suggested that the 

 latter may act as the transmitting agent for the 

 shothole fungus Glceosporium. 



The species of Asphondylia cause the more 

 or less complete destruction of the ovules and 

 developing seeds of prickly-pears, the resulting 

 deformed " fruit" giving rise to a joint or to 

 a " fruit" which in its turn is likely to become 

 infested. Hence Asphondylia is capable iof 

 acting very efficiently in preventing the spread 

 of Opuntias by seed. 



Itonida causes gall-like swellings in the stem 

 joints and has been the cause of heavy loss 

 amongst greenhouse Opuntias. Its native home 

 is not known. 



Many- other insect enemies are known, but 

 they are either not restricted in their dietary 

 to cacti or else their influence in destroying or 

 controlling prickly-pear is not of much im- 

 portance. 



Dr. Howard and Mjr. Hunter, of the Bureau 

 of Entomology, Washington, D.C., have sug- 

 gested certain means by which the introduc- 

 tion of desired insect enemies could be most 

 satisfactorily brought about, and other scientists 

 in California, New Mexico, and Arizona have 

 offered to co-operate. 



In regard to utilisation of prickly-pear as 

 stock fodder, a considerable amount of work 

 has been done, the growing of Opuntias as a 

 farm crop being recommended. It is admitted, 

 however, that prickly-pear, whether grown as a 

 farm crop or as a range crop, is only a roughage 

 and needs to be supplemented by the addition 

 of some more nutritive fodder such as cotton- 

 seed meal, lucerne, bran, &c. Amongst the many 

 rations suggested as suitable for cattle, the fol- 

 lowing may be mentioned as one for a 1,000-lb. 

 milch cow:— 50 lb. of pear, 10 lb. wheat bran, 

 and 10 lb. lucerne daily, the nutritive ratio being 

 1 :5.4. 



In regard to utilising prickly-pear or its 

 constituents in the industries, investigators have 

 been at work in the United States to test the 

 possibility of manufacturing alcohol. The plant 

 mucilage, and the colouring matter contained 

 in the fruits of certain species, have also been 

 examined with a view to determining their 

 usefulness. 



It has been ascertained that if fruits have 

 an average of 10 per cent, of sugar then 140 lb. 

 of fruit are needed to produce one gallon of 

 alcohol. In order to render this a profitable 

 undertaking it is necessary (1) that there should 

 be a large production of fruit per acre, about 

 10 tons per acre being needed; and (2) that there 

 should be some rapid and cheap means of col- 

 lecting the fruit, as gathering by hand, even 

 using cheap native labour, is far too expensive. 

 Then, again, proximity to the distUlery is a con- 

 sideration. This does not exclude its use as a 

 source for immediately potable alcohol. 



The plant mucilage contains galactan and 

 a pentosan. A 10 per cent, "solution" is very 

 viscous, but possesses very poor adhesive qualities 

 and has not been found satisfactory as a glaze 

 even for cheap paper. However, it may serve the 

 needs of other industrial purposes. 



A bright magenta colouring matter is obtain- 

 able from the fruits of certain kinds of prickly- 

 pear, but it does not form a sufficiently fast dye 

 for cotton, silk, &c. It is not suitable as a 

 colouring medium for foods or drugs if sub- 

 jected to light or to oxidation. It is, however, 

 of some use as a colouring matter for ice-cream, 

 beverages, and confectionery. Its extraction does 

 not involve any difficult technical process. 



