1922.] OOJ 



were fi-equently observed during the actual process of emergence, and it 

 was noted that the tough skin of the bean presented a very serious 

 obstacle to the Braconid, so much so that many failed to get clear and 

 died without obtaining their freedom. Each parasitised Bruchus larva 

 ))roduced only a single parasite. Occasionally beans were found which 

 had contained two Bi'itchiis larvae (sometimes one or both parasitised), 

 but each made a separate exit hole. The exit holes of the Sit/aljjhnsure 

 about 1 mm. in diameter, whilst the BrucJiiis makes a much larger hole 

 with a diameter of 2-2*5 mm. It was therefore easy to distinguish 

 between the two, and advantage was taken of this to make some counts 

 which give an idea of the percentage of beetles which had been destroyed 

 by the parasite. The beans were harvested in a number of small lots, 

 usually from single rows, for certain experimental jiurposes ; and in three 

 of these lots, which appeared to be fairly typical of the whole as regards 

 attack by BntcJius, the beans Avere divided into (1) those unattacked, 

 (2) those with a small hole made by Signlphus, and (3) those with a 

 large hole made by Bruchus. The number of beans in each division 

 were then counted with the following results : — 



Lot I. Lot II. Lot IIL 



Number of beaus unattacked 7'2'2 872 120 



„ from which Bruchus emerged .... 204 201 25 



„ „ „ Siijalphus „ 213 325 66 



Percentage of beetles parasitised 51"1 61 "8 72'5 



The percentage of ])arasitisation is high, and the Braconid must 

 have reduced the numbei's of beetles reaching the adult stage by more 

 than half. In all the lots of beans examined, the great majority of 

 those unattacked were of younger growth, as indicated by the lighter 

 colour and general appearance ; very few of the earlier formed beans can 

 have escaped. Of the infested beans, those in which the Bruchus com- 

 pleted its transformations tended on the whole to be smaller and more 

 shrunken than those in which the Bruchus was parasitised. So far,, 

 however, as was observed, the plants resulting this year from beans which 

 had been attacked by the beetle in 1921 did not show any signs of having 

 suffered, and were no less vigorous than those grown from whole seed. 

 The embryo is apparently never, or \gyj rarely, eaten or damaged by the 

 Bruchus larva. There are very few of the beetles to be found in the 

 crop grown this year. 



Sifjalphus liiteipes is, I understand, a known Bruchus parasite. I 

 have not, however, seen any record as regards this particular species.. 

 Elliott and Morley (Trans. Ent. Soc. Lond. 1907, 33, and 1911, 492) 

 give records of various other species of Higalphus which are parasitic oit 



