-i38 MR. A. M. ALTSO.X OX THE LIFE-UISTURY AKB 



(7) [Jnlined puparia, with active Clialcid larvas. (Thefse had, 



superficially, fly-remains.) 



(8) Bi-aconid lined puparia, with dead Chalcid larva\ (The 



Bracouids were in all stages, pup?e predominatiug.) 

 (y) Braconid lined pnparia, with active Chalcid larvae. (These 

 Bi'aconids were in all stages, pupae predominating.) 

 (10) Braconid lined puparia, with some dead Chalcid imagines 

 and larva3. (These consisted, with one exception, of at 

 least one male.) 



The examination of these puparia showed that where super- 

 pai'asitism had taken place, with the exception of a very few 

 instances — the numbers were not noted, — the puparium concerned 

 was a very small one, about the size of M. domestica, and con- 

 sequently, in the case of a blow-fly, a puparium with an exception- 

 ally thin integument. i\nd, further, that the attack of the 

 Chalcid larvJB had taken place in the abdomen of tlie Braconid 

 whei-e this was an advanced pupa, the only part where soft 

 integument exists, due to the distention of the abdomen 

 consequent upon the presence of the meconium (text-fig. 7) : it, 

 therefore, seems conchisive that a JVasonia female is a,b]e to 

 distinguish between a hard sui'face and one yielding to pressure, 

 by means of the apex of her ovipositor. It is worthy to note 

 that Nasonia appeared to be most effective when the IBraconid 

 was a pupa — that is to say, in the identical stage of development 

 to that of its normal dipterous hosts. 



The nmnbers under the heading (B) were (1) 33 pnparia, with 

 Chalcid exit-holes and unlined by the Braconid, presumed pi-i- 

 mary parasitism ; and (2) 17 with Chalcid exit-holes and definite 

 super-parasitisnj. In each instance the puparium had been lined 

 by the Braconid. A feature of these 17 puparia was the position 

 of the exit-hole : in 3 it was made in or about the middle of the 

 puparium, in 6 at the apex of the anterior end, and in 8 at the 

 apex of the posterior end. In only one instance had two efforts 

 been made to escape. This occurred in one of the 3 ; a small some- 

 what elongated aperture had been made in a position diametrically 

 opposed to the exit hole used. A point of great interest in the 

 writer's opinion, with regard to the position of the exit-hole in 

 the above, is that in 6 the Chalcid got out at a point where the 

 Braconid lining is weakest — that is, where it is run over the pi'o- 

 truding chitinized mouth-parts of the late blow-fly larva ; and 

 in 8 the Chalcid got out at the next weakest point — that is, 

 where the lining is run over the blow-fly larva's posterior 

 spiracles. 



The figures under heading (C) are not given in detail ; those 

 for sub headings (1) to (7) do not materially bear on the subject of 

 the investigation, but for 1 and 2 they were very high, and mainly 

 due, in the writer's opinion, to the unshaded position of the glass 

 receptacle and consequent evapoi-ation of any moisture in the 



