such as this Muscidifurax raptor (top) preparing to lay an egg on a fly
puparium, are sold by commercial insectaries as biocontrol agents for filth
flies. The wasp's progeny feed as larvae inside housefly puparia and later
emerge as adults. Emergence holes can be seen in bottom photo. Click an
image for more information about it.
Filth Flies Feel the Heat
By Jim Core
December 29, 2005
Commercial insectaries that produce wasps as biocontrol agents will
benefit from new Agricultural Research Service (ARS) findings showing that killing fly
pupaethe food source for the wasp larvaewith heat shock is an
affordable alternative to irradiation. The heat shock alternative will help
insectaries meet fluctuating demand for two parasitic wasps used to control
House flies and stable flies are nuisances on livestock and poultry
farms, and they transport disease-causing organisms. Parasitic wasps released
as biocontrols can reduce the need for insecticides on livestock and poultry
Wasp species such as Muscidifurax raptor and Spalangia
cameroni lay a single egg inside a fly puparium before it hatches, and the
larva feeds on the fly pupa before emerging as an adult. But it takes one week
to produce fly pupae for the parasitoids, and these live pupae only have a
shelf life of two to three days. So insectaries turned to ARS for help.
J. Geden of the ARS
for Medical, Agricultural, and Veterinary Entomology in Gainesville, Fla.,
studied fly pupae killed with gamma irradiation, cold and heat shock for their
ability to produce parasitoids.
Researchers have reared parasitoids with irradiated pupae for years,
but it's not practical for commercial insectaries. Previous results from
freeze-killing pupae have been mixed. Heat shock killing in an oven had never
been tried before.
The number of wasp progeny, male or female, emerging from pupae killed
by heat shock or gamma irradiation was not significantly different from those
produced on live hosts.
Geden found heat-killed, irradiated and freeze-killed pupae stored in
refrigerated plastic bags remain as effective for production of M.
raptor as live pupae for as long as four months.
Production of S. cameroni on heat-killed and irradiated pupae
was equal to parasitoid production on live pupae for up to two months of
storage. After that, production declined to 63 percent of live pupae.
Production of S. cameroni on freeze-killed pupae was about 75 percent of
production using live pupae for eight weeks of storage but declined rapidly
ARS is the U.S. Department of
Agriculture's chief scientific research agency.