205 



of little value when compared with the cost of attending to the traps. Bishopp 

 (Farmers' Bull. 734, U.S.D.A., 1919) stated that "there is a general tendency 

 for those engaged in combating flies to put too much dependence on the fly 

 trap as a means of abating the nuisance. It should be borne in mind that fly 

 trapping is only supplementary to other methods of control, most notable of which 

 is the prevention of breeding either by completely disposing of breeding places, 

 or by treating the breeding material with chemicals." 



Some birds are known to catch and kill adult flies, as also do certain 

 fossorial wasps known popularly as "policeman flies." Froggatt reported that 

 Stisus tnrncri, Stizus sp., and Nysson sp., were known to act in this way (1917). 

 Mr. Hacker, of the Queensland Museum, has informed me that the wasps 

 Sericophorus chalyhaeiis and 5'. rclucens are known to catch sheep maggot-flies 

 in South Australia and Queensland, respectively. He also stated that the latter 

 wasp was probably that referred to by Froggatt (1915, p. 39) as Gorytes sp. How- 

 ever, these active wasps are not numerous and seem to exert little influence on 

 fly investation. In Britain the dung fly Scatophaga stercoraria has been reported 

 by Lefroy to be a predator on blowflies, but its value as a controlling agent is 

 doubted by Austen (Ann. Mag. Nat. Hist., 8 (43), 1921, p. 118). 



We may now briefly consider the possible biological control of the fly 

 problem by utilizing the parasites of, and predators on, the maggot and pupal 

 stages. Amongst the predators on larvae one might mention insectivorous 

 birds, various ants, including the small red ant Pheidole megaccphala, as well 

 as Staphylinid (Creophihis) Histerid and Carabid beetles and even mice. 

 Pupa are found to be preyed upon by the larval stage of a small species of 

 Histerid (Sapriniis sp.) in Brisbane. It is, however, from parasitic wasps that 

 better results are hoped for. Quite a number are known to occur in Australia, 

 the following having been reported as attacking the maggot stage and destroying 

 the fly while in the pupal condition: — Australencyrtns giraulti, Johnston and 

 Tiegs (perhaps better known a^ Tachinaephagus giraultiS^^ ) ; Hemilexomyia 

 abriipta, Dodd ; Chalcis calliphorae, Froggatt ; and probably C. dipterophaga, 

 Girault and Dodd. Of these, all but the first-named are rare and apparently 

 of little value. A. giraulti has been studied by Johnston and Tiegs (1921, pp. 

 107-110), but very little is known regarding the life history of the others. 



Of those which are known to parasitise the pupal stage, the most important 

 is Nasonia ,hrevicornis, G. and S. (probably more correctly known as A^. 

 ahnormis, Boh.), others being Spalangia muscidarum, Rchdsn. ; Dirhinus 

 sarcophagae, Froggatt ; and Paraspilomicrus froggatti, Jnstn. and Tiegs. Nasonia 

 has been widely used against the blowfly in sheep country in Eastern Australia, 

 especially in New South Wales, being distributed from Mr. Froggatt's labora- 

 tory. The habits of this insect have been studied by him and his colleagues, 

 J. L. Froggatt and McCarthy (1914, 1915, 1916, 1917, 1918, 1922), as wefl as 

 by myself and Tiegs (1921, 1922). The biology of the remaining three has 

 also been investigated in my laboratory (Johnston and Bancroft, 1920; Johnston 

 and Tiegs, 1922, a, b). Of all the parasitic wasps, mentioned above, only two 

 seem to be likely to have any serious effect on blowfly increase, vi:;., Aus- 

 tralencytus and Nasonia. The former has not been tried out in the field, while 

 in regard to the latter there is considerable diversity of opinion as to its utility, 

 the question having been discussed in some detail by Johnston and Tiegs (1922, 

 a, b). Nasonia will readily parasitise practically all available pupae, but is 

 unable to penetrate even half an inch of soil in order to reach them ; hence its 

 attacks are limited to such pupae as occur in readily accessible situations. 



(1) Mr. A. A. Girault has informed me that Australencyrtns is a synonym of Tachinae- 

 phagus. The species has been figured by Froggatt (1922) as Stenostcrxs fnlvoventralis, 

 Dodd. 



