230 MR. A. M. ALTSON ON THE LIFE-HISTORY AND 



The hosts reported from America 1)V Giraiilt and Saunders (6) 

 are : — 



Musca domestica Linn. 

 Ccdliphora erytlwoce'pliula Meig. 

 Phormia regina Linn. 

 Lucilia ccesar Linn. 



,, sei'icata iVleig. 

 Chrysomia macellaria Fabi\ 

 Cynomyia cadavermia Desv. 

 Sarcoj^haga species " K " (.Spec. nova). 



Tlie hosts reported from Australia by Fi-oggatt, jun. (7) are as 

 follows : — 



Fycnosoma rufifacies. " Mostly in the field." 



,, varipas. " To a lesser extent in the field." 



Anastellorhina augur. ^ 

 PoUenia stygia. I 



Lucilia sericata. > "In the ]aboratorJ^" 



Galliphora erythrocephala. i 

 Sarco])haga aatrifrons. ^ 



Super-parasitism, or Accidental Secondary Parasitism. 



That Nasovia hrevicornis might be a " H3'perpara site" upon 

 Alysia manducator originally occui'red to the writei', when the 

 second lot of puparia were collected from the spot at Regent's Park 

 whence the original Braconid parasitized material was obtained, 

 and when it was found that this Chalcid was emerging from it. 

 However, no Braconid lining to the pupaiia was observed, at the 

 time, in any from which the Chalcids had emerged ; and as the 

 initial breeding operations showed that the latter — then undeter- 

 mined — bred freely from healthy host puparium, it was assumed 

 that " hypei'parasitism " was not the role of N. hrevicornis ; 

 although it appeared reasonable to suppose that the Chalcid 

 might act accidentally as a secondary parasite in the early stages 

 of development of the Braconid — that is, during the first or 

 second instar — and when the greater part of the fly-nymph still 

 existed. That secondary parasitism in this early stage could 

 take place appeal's probable ; and it does not require a great 

 stretch of imagination to conceive the race for life within a 

 puparium, in the fly-n3anph of which an early instar larva of the 

 Braconid is slowly feeding, when suddenly one by one a dozen, 

 more or less, Chalcid ]arv?e commence feeding operations fi-om 

 the outside of, and through the envelopiug integument of the fly- 

 nymph. That the result of such an unequal contest would be 

 against the Braconid, it seems only reasonable to assume ; and 

 that the latter would eventually be killed by the Chalcids biting 

 into it. ISIo efforts were made to investigate this point; it 

 appeared too obvious a potentiality, and to seai'ch the remnants 



