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AN ECONOMIC STUDY OF NASONIA BREVICORNIS, A HYMENOPTEROUS 

 PARASITE OF MUSCID DIPTERA. 



By John L. Froggatt, B.Sc. 



In considering the methods of coping with any group of injurious insects, the study 

 of natural enemies must occupy an important place in any laboratory or field 

 investigations that are carried out in connection with such pests. 



When investigations concerning the sheep-maggot fly pest were commenced in 

 New South Wales in 1913, careful search was made for any natural enemies in the 

 field, and in November of that year pupae of Pycnosoma (Calliphora) rufifacies were 

 found heavily parasitised by a small Chalcid wasp. This discovery was made on 

 Yarrawin Station (Messrs. Dickson Bros.) in the Brewarrina district, under the 

 remains of a dead foal. The carcase was lying on the edge of a patch of scalded 

 ground, with a little timber about 100 yards away. On pulling the remains apart, 

 a large number of pupae of Pycnosoma rufifacies were exposed ; from some the flies 

 had already emerged, many others were intact. Some of the intact pupae were 

 carefully opened with the point of a penknife, and were found to contain a number 

 of small, white, creamy, brown or black objects, these being the larvae, early' pupal, 

 and late pupal stages of the parasite wasps. A few of the intact pupae that could 

 be found were collected for further study and observation ; some were retained at 

 the Experiment Station, and the remainder taken to the Entomological Department, 

 Sydney. An average count of a number of these parasitised pupae gave the result 

 of about 20 wasps per pupa. 



Before proceeding further, a consideration of the distribution of this wasp should 

 prove of interest. Within a few days of the above-mentioned discovery this 

 parasite was found under similar circumstances at Longreach, Central Queensland. 

 Specimens of the wasp sent to Dr. Howard, Chief of the Bureau of Entomology, 

 Washington, U.S.A., by the Government Entomologist of New South Wales were 

 identified as Nasonia brevicornis, a Hymenopterous parasite that had been originally 

 described by Messrs. Girault & Saunders, who bred it from the pupae of the common 

 house-fly (Musca domestica) at the Illinois Entomological Station at Urbana in 1908. 

 It has also been reported from Chili ; and the British Museum has received specimens 

 of it from India. Future researches may reveal that its range is only restricted by 

 the distribution of the Muscid flies. 



Further observations in New South Wales have shown that it is only scattered 

 thinly over most parts of this State and is doing valuable work in preventing the 

 breeding of the flies by their destruction in the pupal condition. Probably it is to 

 be found over the greater part of Australia. 



The breeding of these wasps has been carried on continuously and systematically 

 from those bred from the parasitised pupae in November 1913, the wasps now being 

 used in the cages for the purposes of propagation being the direct progeny of those 

 obtained from the original lot of pupae. On a few occasions additions have been made 

 by introducing fresh specimens of Nasonia brevicornis collected in the field. : (See 

 paper in the Agricultural Gazette of N. S. Wales, September 1914, McCarthy's 

 observations). 



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