Stanley W. Bromley.
Bee-killing Asilids in New England.
Psyche 49(3-4):81-83, 1942.

This article at Hindawi Publishing: https://doi.org/10.1155/1942/16348
CEC's scan of this article: http://psyche.entclub.org/pdf/49/49-081.pdf, 276K
This landing page: http://psyche.entclub.org/49/49-081.html

The following unprocessed text is extracted automatically from the PDF file, and is likely to be both incomplete and full of errors. Please consult the PDF file for the complete article.

BEE-KILLING ASILIDS IN NEW ENGLAND
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-bees7 although I listed certain species such as Proctacanthm philadelphicus Macq. and Diogmites (Dero- myia) ambrinus hew 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 Pmmachus fitchii 0. S. the famous old "Nebraska bee- killer7' 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 ha~elds which7 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 fitchii 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.




================================================================================

82, Psyche [Sept ,-Dec.
A summary of the records I have collected of honey-bees falling victims to Asilids in New England between 1911 and 1941 follows. These observations were made largely at South- bridge, Massachusetts; Wallingf ord and Stamford, Connecti- cut ; and nearby areas.
Number of
instances of
Asilid species honey-bee prey
Promachus fitchii 0. S. ...................... 56
Diogmites umbrinus Loew ................... 40 Proctacanthus philadelphicus Macq. .......... 2 2 P~octacanthus YU~US Williston ................ 14 Promachus bastardii Macq. .................. 11 Diogmites discoZor Loew .................... 7 Bombomima thoracica Fabr. ................. 2 Bombomima grossa Fabr. ................... 1 Bombomima jlavicollis Say .................. 1 Proctacanthus b~evipennis Wied. ............. 1 ........................... Erax astuans L. 1 Of these 11 species, Diogmites discolor is restricted to the extreme southwest corner of Connecticut, Proctacanthus rujus to certain sand plains or washouts along some of the larger streams and rivers, Bombomima possa is decidedly uncom- mon, and P~octacanthus brevipennis is found almost exclu- sively in level sandy open woods. The remainder are wide- spread and locally abundant. Erax astaans is probably the most abundant and generally distributed of Southern New England Robber flies.
C. W. Johnson's list of N. E. Diptera (1925) recorded 86 species of Asilidz in New England. Of this number it may be seen that only 11 species ordinarily kill honey-bees and of these only 3 or 4 at most may kill bees in any quantities. Even with the leading species on the list, P~omachus fitchii, it would be very rarely that the effect of bee-killing by this insect on a commercial apiary would be felt.
In fact, it would seem quite probable that any possible loss which P. fitchii might occasion to bee-keepers would be more than counterbalanced by the control of PhyZZophaga grubs ex- erted by the larvz of this fly. Such benefits, however, would be much less apparent now than thirty years ago due to the



================================================================================

decline in the utilization of grass for hay and the abandonment of mowing in many parts of New England as a result of the displacement of the horse by motor driven vehicles. Promachus fitchii tends to disappear from hayfields after they have been abandoned and an old-field succession of vary- ing stages from grasses to shrubs and trees takes place. So after all, the species begins to lose any significance it might have had as a bee-killer thirty years ago, with the changing times and conditions of more recent years.



================================================================================