79 



142) and 0. convexa (1912, p. 291), referred to 

 to the fact that their fruits are sometimes proli- 

 ferous, but did not suspecl* the cause of the 

 alteration. 



These larvae were seen crawling amongst the 

 g'all-like bodies that represented the ovules 

 formerly present when insect attack had com- 

 menced. Their occurrence was noticed even in 

 altered " fruits " which had already, in the 

 course of vegetative growth, given rise to fairly 

 large stem-joints. Since there were no signs what- 

 ever of recent fly attack or of insect emergence, 

 the presence of these insects in such cases must 

 be accounted for either by pedogenesis such as is 

 known to occur in another Cecidomyiid genus, 

 Miastor, in Europe (Wagner, Meinert) and North 

 America (Felt, 1912, p. 753), or by the occur- 

 rence of a very protracted life, extending over 

 many months. Dr. Griffiths believes the latter to 

 be the true explanation. He has given some 

 attention to this parasite (1913, p. 20), and dur- 

 ing an interview informed us that the eggs are 

 deposited from February to April, the larva 

 living in the fruit and, after pupating, emerging 

 as an adult next spring just about the time that 

 the prickly-pear blossoms; also that the joints 

 or fruits, which develop on the parasitised and 

 deformed ' ' fruit, ' ' originate during the year that 

 infection has occurred. The Commission's obser- 

 vations of the occurrence of the larva were made 

 in November and December, which would thus 

 point to a ten or eleven months' duration of the 

 larval state. 



The proliferation of the fruit would in most 

 cases give rise only to a single joint or a single 

 plant, whereas if seminal development had not 

 been frustrated by the insect, a large number of 

 new plants would perhaps have been produced 

 from the seeds. The effect of this parasite, then, 

 is such that the chances of an increased area of 

 distribution of the plant are greatly lessened. 



Subsequent to the Commission's investiga- 

 tions in the United States, Mr. E. P. Felt, in a 

 letter dated February, 1914, has tendered the 

 following information: — "Mr. E. 0. Essig, Secre- 

 tary of the State Commission of Horticulture, 

 Sacramento, California, forwarded specimens of 

 Asphondylia opuniim, accompanied by the state- 

 ment that practically every fruit in a large 

 district was absolutely ruined by this insect, 

 many of them having several hundred in each. ' ' 

 He. further adds that it should be comparatively 

 easy to introduce this insect into Australia if it 

 is desired. 



Two other species of Asphondylia are 

 known to infest prickly-pears — ^viz., A. ietheli, 

 described by Cockerell (1907, p. 324), from mal- 

 formed "fruit" from Colorado, and A. arizo- 

 iiensis Felt, recorded as producing a fruit-like 

 gall in a species from Arizona (Felt, 1908, p. 

 378; 1908&, p. 294). An account of the former 

 is also given by Felt (1908, p. 376; 1912, p. 6). 

 In regard to the latter, Mr. Felt has informed 

 us that it attacks the fruit, causing the forma- 

 tion of a gall half the size of a man's head, one 

 being figured in "Nature" (23, 1882, p. 77). 



Other Diptera. 

 Various other diptera are found associated 

 with prickly-pears and other cacti, but are mainly 

 scavengers. They may be important since, when 

 opportunity offers, they increase the injury 

 caused by other insects such as Melitara and 

 Moneilema, or even Chelinidea and Gersteckeria. 



The chief of these scavengers in the United 

 States (C.I., pp. 37-38) are — Copestylum margi- 

 naium, Say; four species of Volucella, two of 

 Hermetia, and Stictomyia longicornis, Bigot. 



"White Ants. 

 The galleries of Termites or white ants were 

 seen rather commonly in parts of Texas on the 

 roots and stems of prickly-pears, especially those 

 which had been injured by ' ' pear rats ' ' and other 

 rodents. It has been stated (C.I., p. 40) that 

 Termes flavipes, KoUar, may attack young 

 Opuntias and Cereus in Texas, forming covered 

 galleries on the segments, while the nest is not 

 infrequently made in decaying joints. 



Summary of Evidence Regarding Insect 

 Enemies of Prickly-pear in U.S.A. 



In the Bulletin on Cactus Insects (p. 13) 

 there is given the following list of the principal 

 species in the order of their importance as 

 prickly-pear pests in the United States: — (1) 

 Chelinidea, 3 species; (2) Mimorisia flavidissi- 

 malis; (3) Narnia, 4 species; (4) Melitara, 4 

 species; (5) Moneliema, 8 species; (6) the "Wild 

 Cochineal Insects, Coccus conftisus and C. tomen- 

 tosus; (7) Marmara opuntiella; (8) Asphon- 

 dylia, 3 species; (9) Stylopidea picta; (10) 

 Diaspis; (11) Orzamia ludicalis; (12) Platy- 

 nota rostroma; (13) Polistes, 3 species. Nos. 

 11, 12, and 13 are Hymenoptera, which feed on 

 the fruit. It will be noticed that in this list the 

 Cactus weevils ( Gerstoickeria, spp. ) are not given 

 a place. 



The period of the year during which the 

 investigations were carried out in the United 

 States was the aiitunm, and naturally insect 

 activity was not at a maximum. The destruction 

 caused by many of the pests which are regarded 

 by Messrs. Hunter, Pratt, and Mitchell as being 

 of prime importance — e.g., Chelinidea, Narnia, 

 and even Mimorista — ^was not as evident as that 

 caused by Melitara, which seems to be the most 

 destructive and one of the most wide-spread of 

 all the genera of cactus insects in the^ United 

 States. It should be remembered that the investi- 

 gations of the Bureau of Entomology were carried 

 out mainly in Texas, where Melitara appears 

 to do very little damage. Moneilema, spp., though 

 wide-spread, do not seem to be sufBciently 

 numerous to cause any great destruction. Judg- 

 ing from the results noticed in the New York 

 Botanical Gardens, Itonida opuntim should 

 occupy a prominent position amongst the 

 destroyers of prickly-pear. 



As a result of the investigations in the 

 United States, the Commission considers that the 

 following insects are the most effective enemies 

 of prickly-pear there:— Melitara, spp.; Mimo- 

 rista flavidissimalis; Moneilema, spp.,_ Goeno- 

 poeus palmeri; Chelinidea, spp.; Narma, spp.; 

 Gerstceckeria hulhardi; Itonida opuntim; and 

 Asphondylia opuntim. 



Proposed Introduction of Cactus Insects 

 into Queensland. 

 The advice of Dr. Howard, the Chief of the 

 Bureau of Entomology, and one of his senior 

 officers Mr "W. D. Hunter, was sought regardmg 

 the introduction of these into Queensland Neither 

 of these entomologists foresaw any likelihood ot 

 the above-mentioned insects attacking plants other 

 than Cactacese. They would not, however, advise 

 the introduction of the Calandrid weevils, Cacto- 

 phagus, spp. 



