40 



MASS. EXPERIMENT STATION BULLETIN 249 



NUMBER OF BEETLES- 2607 



Figure 8. Time when Flnm Curculio Beetles Enierg"ed from the Soil in 

 Breeding: Cag°es in the Insectary, Waltham., Mass. 



Birds and Predatory Insects. 



Although plum curculio beetles are hard and apparently unpalatable food, 

 the U. S. Biological Survey (9) has found them in the stomachs of orioles, 

 grosbeaks, barn swallows, vireos, and thrushes. However, these birds are not 

 sufficiently abundant to provide a noticeable check on this insect. 



The grubs are known to be eaten while in the ground by various ground 

 beetles and ants, while lacewings attack the larvae in the fruit, but no 

 outstanding instance of a significant check by predaceous insects has been 

 brought to the attention of the writer in Massachusetts. 



Parasites. 



During the observation and rearing of several thousand plum curculio in 

 1926 and 1927 at Waltham, no parasites were found. In 1928, however, six 

 specimens of a tiny four-winged parasitic fly, tentatively determined as 

 Triaspis aurculionis Fitch, were reared from a large lot of field collected 

 larvae. Records of this parasite in other states show a maximum parasitism 

 of 25 per cent (9), although the general average is less than 3 per cent. 



