Parasitism of house and stable fly pupae in different microhabitats by Spalangia cameroni (Hymenoptera: Pteromalidae)

The use of pupal parasitoids in augmentative biological control has become increasingly popular with horse owners as house and stable flies (Diptera: Muscidae) have become more resistant to insecticides.  Nevertheless, parasitoid augmentation on equine facilities could be improved significantly by better understanding the biology of regionally dominant parasitoid species, including the occurrence and abundance of species and the microhabitat cues associated with host location.  Spalangia cameroni (Diptera: Pteromalidae) was the dominant species in surveys conducted on equine farms in North Florida.  This species accounted for 86.1% of parasitized pupae from six common substrates.  Therefore, S. cameroni was tested in the laboratory for microhabitat preferences associated with these substrates containing either house or stable fly pupae.  Parasitism of the filth fly pupae was assessed at a high (20:1) and low (5:1) host:parasitoid ratio.  Parasitoid progeny production and total mortality of fly pupae was greater at the higher ratio.  Though S. cameroni exhibited diminished habitat preference with fewer hosts, clear selection of pupae at higher densities in certain substrates suggested that the parasitoids may be attracted to volatile cues.  Experiments are being conducted in an attempt to isolate and identify chemicals that attract the parasitoids.