67 



could be stored up for winter use. He also 

 stated that these animals fed largely on cactus 

 during dry seasons, depending on it for much of 

 their supply of moisture. In his work (p. 112) 

 he mentioned that ordinarily these rats were of 

 little economic importance, owing no doubt to 

 their spread being controlled by their natural 

 enemies, e.g., hawks, owls, rattlesnakes, and car- 

 nivora. During the interview he stated that in 

 some parts of Texas and Arizona wood rats had 

 become sufficiently numerous to lead to the 

 receipt by the Bureau of Biological Survey at 

 Washington, D.C., of requests for information 

 regarding means for their destruction, this result 

 being no doubt due to the diminution in the 

 number of camivora and snakes frequenting those 

 localities. 



Both Mr. Hanshaw, the Chief of that 

 Bureau, and Mr. Bailey were of opinion that the 

 introduction into Australia of any of these rodents 

 would be dangerous, since they would not confine 

 would be dangerous, since they would not confine 

 their attention to prickly-pear, nor would they 

 destroy it except locally during seasons when 

 other food was scarce, so that the total injury 

 which they might occasion would be quite in- 

 sufEcient justification for such action. 



Dr. Merriam, formerly Chief of the Bureau, 

 also stated that reliance could not be placed on 

 the cacticidal habits of any of these rodents, 

 and moreover, that these animals occasionally 

 served indirectly to spread prickly-pear. 



Though prickly -pear enters very largely into 

 the diet of certain species, it will be recognised 

 that the introduction of these rodents could not 

 be recommended on account of the probability 

 of their becoming a nuisance. 



Besides the various species of Neotoma, other 

 rodents such as jack rabbits, cotton-tail rabbits, 

 and some gophers, were mentioned by Professors 

 Thornber, Merrill, and Hammond as being 

 destructive to pricldy-pear, particularly the less 

 spiny species, during winter and early spring, 

 and especially during dry seasons, more suitable 

 food being scarce during such times. Mr. J. D. 

 Mitchell had observed the same result in Texas, 

 while the Commission noticed injuries to Opun- 

 tias caused by various rodents in Texas, New 

 Mexico, Arizona, California, and Kansas. Dr. 

 Griffiths (1909a, p. 19) and also Dr. Wooten 

 (1911, pp. 14-17) referred to their destruction of 

 young and relatively spineless plants. 



Mr. Bailey in the work mentioned earlier 

 (1905) has stated incidentally that he found 

 parts of prickly-pear, especially the fruits or 

 seeds, in the alimentary tract of certain squirrels, 

 Ammospermophilus interpres (p. 83), Gitelhis 

 variegatus buckleiji, Slack (p. 85), C. variegatus 

 grammariis, Say (p. 86), and C. tridecimlineatus 

 pallidus, Allen (p. 87). 



Amongst the rodents which may utilise 

 prickly-pear plants for shelter and occasionally 

 for food are the Texan cotton rat, Sigmodon hes- 

 pidus texanus, Aud. and Bach. (p. 115) ; certain 

 gophers, Thomomys aureus lactuquilla, Bailey (p. 

 134), and T. perditus, Merriam; Dipodomys ela- 

 ior, Merriam (p. 148), and B. merriami (p. 150) ; 

 the jack rabbits, Lepus texanus, Waterhouse (p. 

 153), and L. floridanus clmpmani, Allen (p. 156) ; 

 as well as the so-called prairie dog, Cynomys 

 ludovicianus, Ord. It must be remarked that the 

 above list of rodents refers to the species found 

 in Texas, and wauld doubtless be greatly 



lengthened if work similar to that carried out by 

 Mr. Bailey were undertaken in other parts of 

 America. The common jack rabbit of Arizona, 

 which is known to feed on pricldy-pear when 

 other food is scarce, is Lepus arizonice. 



Mr. Bailey (1905, p. 75) found parts of 

 prickly-pear plants in the digestive tract of the 

 mountain sheep, Ovis mexicanus Merriam. 



DESTRUCTION BY INSECT ENEMIES. 

 In December, 1912, the U.S. Department 

 of Agriculture published a bulletin by Messrs. 

 Hunter, Pratt, and Mitchell, dealing with the 

 principal cactus insects of the United States. 

 It contains a short account of some of the more 

 important of them, as well as some fine illus- 

 trations of the insects and their work. It also 

 includes a list of injurious species, together with 

 their known parasites, and of the scavengers and 

 other insects more or less incidentally associated 

 with cacti. This work has been freely used in 

 the writing of this portion of the report. 



The chief enemies of the prickly-pears are 

 either beetles, plant-bugs, moths, or diptera. 



The Colbopteeous Pests. 

 Cactus Longicorns, Moneilema, spp. 



The members of this genus of " Cactus 

 Longicorns ' ' are rather large, wingless, generally 

 black beetles (C.I., pi. 1),* which in the adult 

 stage feeds on the segments of Opuntias, but 

 which in the larval condition bore down into the 

 joints and stems and even the roots, feeding on 

 the internal tissues, a large tunnel being formed. 

 The presence of larvaj is often indicated by the 

 occurrence of a hard, black, gummy-like exudate 

 from the plant at the point of entry of the larva 

 (C.I., pi. 2). Pupation takes place in an im- 

 perfect cocoon, generally just below a joint lying 

 on the ground. This cocoon, in the case of M. 

 crassum at least, is made of fibre of the food- 

 plant and covered externally with sand. There 

 is said to be one generation per season. The 

 adults (of M. crassum) are commonest in April 

 and May, and again in September (C.I., pp. 

 13-14), or even later according to our observa- 

 tions. This suggests the occurrence of two 

 broods. 



It is stated that eight species are known to 

 affect the roots and stems, but some of these are 

 recorded only from Mexico. The common species 

 in Texas are M. crassum (Le Conte) and M. ulkei 

 (Horn) , M. spoliatum (Horn) being less common. 

 In Kansas there occur M. amdatum (Say) and M. 

 semipunctaium, Le Conte (Popenoe, 1877, 1878). 

 The abovementioned species are recorded as in- 

 juring Opuntia, M. crassum, attacking Echino- 

 cereus also. Hubbard (1899) found M. gigas (Le 

 Conte) to be an enemy of the giant cactus {Gar- 

 ncgiea gigantea) in Arizona. Schwarz (1896, 

 1899) has also referred to some of these species 

 of Moneilema as injuring cacti. 



G. H. Horn in his monograph (1885, pp. 

 180-190) refers to the foUowing species:— M. 

 anulatum, Say (Colorado, New Mexico Texas) ; 

 M apivessuvi, Le Conte (Arizona, New Mexico) ; 

 M (liqas, Le Conte (Arizona) ; M. semipunctatvm, 

 Le Conte (Lower California); M. IccVigatum,, 



* The alii^^^l^ti^^r^^cl^^^^'li^^^ l?^r'S,v^f«'!i 

 Hunter, Pratt, arid Mitchell'|pap« on "the Principal 

 eaatus Insects e{ the tfriited States," 1912. 



