196 MR. A. M. ALTSON ON THE LIFE-HISTORY AKD 



that keep down the pest here : and the accidental discovery at 

 the Society's GJai-dens of three important checks gave the work a 

 start. In this communication two Hymenopterous parasites are 

 discussed : other parasites are under investigation. 



Acknowledgments are due to the Australian Commonwealth 

 Government for a small grant to assist the work. 



H. M. Lefroy. 



A Short Account of the Start of the Work. 



About the last week iti June Prof. Maxwell Lefroy gave the 

 writer a tin containing approximately 1500 Dipte]'ous puparia 

 to breed out. These had been forwarded by Miss Cheesman, the 

 Society's Assistant Curator of Insects. 



The contents of the tin were divided into five lots, and put into 

 an equal number of jars containing damped soil. Tlie jars were 

 covered with muslin. (At the outset, it should be explained that 

 occasional damping of soil was necessitated by the fact that the 

 .soil was kept in sacks in the laboratory, and consequently any 

 moisture originally in it soon evaporated.) 



Adult flies began to emerge a week later, and continued to do 

 .so for a period of six or seven days. They were identified as 

 Callvphora erythrocephala Meig. 



The jars containing the empty puparia and a large number 

 of intact puparia were then put aside. They were occasionally 

 examined, and on 14th July the first jar inspected was found to 

 contain an active Hymenopteron, which upon closer observation 

 appeared to be a female Braconid ; the examination of the other 

 four jars showed that three of them also contained specimens of 

 the Braconid. As the remaining ja.r did not contain any Braconid, 

 the contents were emptied and cirefully examined; all empty 

 puparia were separated from those which were still intact, and 

 six of the latter were opened, with the result that two were found 

 to contain fully-formed flies which had failed to emerge, another 

 a shapeless, smelling, moist mass — an atrophied fly-nymph — and 

 the other three contained Braconids, one in an early pupal state, 

 the others fully-formed adults apparently ready for emergence, 

 free of the pupal skin, and wings fully expanded*. 



With the appearance of this parasite, breeding experiments 

 were commenced. The Braconids were released in a muslin- 

 covered glass cylinder, which was placed in a large tray containing 

 soil. Food was put in. 



Blow-fly larvfe and eggs were obtained by exposing meat at the 

 Zoological Gardens and on the balcony of the Imperial College of 

 Science, South Kensington, and a test made to ascertain if the 

 Braconids would parasitize the larvae. The test was satisfactory, 

 and one female began ovipositing one minute after the admission 

 of the larvfe, and in 25 minutes five females were at work. 



* Both insects crawled out of their opened puparium : one at once passed the 

 meconium and discharge, the other did not : both were males. The former lived a 

 normal period, the latter was dead on the second day. 



