EVIDENCE OF HONEYDEW FEEDING IN BLACK FLIES (DEPTERA: SIMULIIDAE)

Black flies (Diptera: Simuliidae) were collected from a tamarack stand, Larix laricina (Du Roi) Koch, heavily infested with Adelges lariciatus (Patch) (Homoptera: Adelgidae). Insect nets were used to sweep the tamarack branches to capture black flies associated with the trees. Six black fly species were sweep-netted, with 85.5% of all flies belonging to Simulium venustum Say complex. Samples of honeydew and the crops and midguts of individual black flies were tested by thin layer chromatography using fructose, glucose, sucrose, turanose, melezitose, raffinose, and stachyose as standards. The sugars fructose, glucose, sucrose, raffinose, and stachyose were found in the adelgid honeydew samples. Of the 201 black flies tested, 194 contained sugars, which occurred in 16 combinations. It is argued that stachyose can be used to indicate when black flies have fed on the adelgid honeydew. We conclude that 49.7% of the S. venustum collected from the tamarack had fed recently on this honeydew source. In addition, it was observed that black flies reared in the laboratory readily ingested freshly excreted and older (dry) honeydew when presented with branches from the tamarack stand.