"5(5" [March, 



NOTE ON SOME HYMENOPTEEOUS PARASITES AND OTHEE ENEMIES 

 OF TORTRIX riRIDANA LINN.: WITH FUETHER EECORDS OF 

 CHALCIDIDAE SWAEMING IN BUILDINGS. 



BY HUGH SCOTT, M.A., SC.D.,' T.E.S. 



The two subjects mentioned in the title may at first sight seem 

 quite unrelated one to the other, but in reality there is a connection 

 between them. In tlie "Entomologist's Monthly Magazine " for Jan. 

 1919, p. 13, I published an account o£ the occurrence of vast swarms of 

 females of the Chalcidid Pferomalus deplaiiatus Nees in certain houses 

 for several seasons in succession. Names of a number of insects said to 

 be hosts of this parasite were collected from the literature, and it was 

 shown to be very unlikely that the swarms were derived from Anobiid 

 beetles in the woodwork of the buildings (as had been supposed), but 

 much more probable that they were parasites of the too abundant 

 Tortrlx viridana. Proof is now forthcoming that this moth is a 

 host (though not the only host) of the Pferomalus, as in 1921 I bred 

 43 examples of the latter, all apparentlj^ females, from pupae of the 

 Toririx. The purpose of the present paper is to give particulars of 

 this, and of the breeding of three other species of parasites (Ichneu- 

 monidae) from Tortrix viridana ; a brief note on other enemies of this 

 moth ; and, finally, to place on record certain further occurrences of 

 swarms of Chalcidids, both Pteromalns deplanatus and Stenomahfs 

 i/itiscarum, in buildings. Certain works have been consulted, but the 

 literature has not been exhaustively searched, my purpose being mainlv 

 to put on record my own observations, to be made use of by other 

 workers if needed. 



I. BREEDING OF PTEROMALUS BEPLANATUS FROM 

 TOR TRIX VI RID A NA. 



A number of pupae of the Toririx were collected on June 7th. 1921, 

 l)y beating oak-trees in a wood in the Southern part of Cambridgeshire. 

 The pupae were placed on some soil in a glass bowl with gauze stretclied 

 over the top, and the soil was occasionally lightly moistened. When a 

 series of the moths had emerged, there remained some abnormally small 

 and sliort pupae, from which tlie Chalcidids issued as follows : — 19 came 

 out from two pupae on June 29th ; these were removed that day, and 

 12 more emerged from a single pupa on June 30th or 3\\\j 1st; finally, 

 on July 6th the remaining pupae were broken open and examined, and 

 from one of them 12 more examples of the Pferomalus ran actively out. 

 The 43 CMiak'idlds therefore emerged from four pupae, and in two cases 

 the actual number from a single pupa was seen to be 12. In each 



