1942] 
Bee-killing Asilidoe 
81 
BEE-KILLING ASILIDS IN NEW ENGLAND 
By Stanley W. Bromley 
Bartlett Tree Research Laboratories, 
Stamford, Connecticut 
While Robber flies have been reported as destructive to 
honey-bees in Nebraska, Missouri, Texas, Florida and other 
Southern States, no species has been noted as of economic im- 
portance in this respect in New England. 
In my observations on the prey of Robber flies in south- 
central Massachusetts as reported in Psyche, December 1914, 
p. 192, I mentioned that I had not observed Asilids feeding to 
any extent on honey-bees, although I listed certain species such 
as Proctacanthus philadelphicus Macq. and Diogmites ( Dero - 
myia) umbrinus Loew as partial to worker vespids. 
A few years later, however, a situation came to my attention 
where Asilids were attacking bees extensively. This observa- 
tion is here published for the first time. The species concerned 
was Promachus jitchii O. S. the famous old “Nebraska bee- 
killer” whose habits were first described by Fitch in his New 
York report of 1864. 
About a mile and a half south of Southbridge, Massachusetts, 
lies a large drumlin called Lebanon Hill. Part way up the hill 
was an apiary of 15 or 20 hives. Adjacent to the bee yard were 
several dry hayfields which, although mowed yearly, were 
reaching a condition described as “run-out” by the farmers, 
because the better grasses were beginning to give way to such 
plants as ox-eye daisy, sorrel and black-eyed susan ; a condition 
very probably due to white grub infestations. The dominants 
were, however, still timothy, red-top and some scattered clover. 
These hayfields were fairly seething with Promachus jitchii 
and I soon saw that the majority of prey taken by them con- 
sisted of worker honey-bees. On July 10-13 (1915) and July 
15 (1916) I collected 42 of these flies, both males and females, 
each with a honey-bee as prey. This represented in all about 
three hours collecting. 
