Yellow-faced Blowfly

Appearance

''C. mortuorum'' is a deep blue-green shining metallic fly with a yellowish face and jowls, possessing a body length of 8–15 mm. This fly is a cold-adapted blowfly originally named by Carl Linnaeus in 1761.

The genus ''Cynomya'' is generally identified by their lack of presutural intra-alar seta. Also, this genus has a shining abdomen, and when they are viewed from the posterior, no microtomentum can be seen.

Within this genus, there are two species that can be commonly confused: ''Cynomya mortuorum'' and ''Cynomya cadaverina''. However, looking at specific characteristics can help separate these two species.

First, ''C. mortuorum'' has bright yellow to orange gena, or cheeks, and parafacials, whereas ''C. cadaverina'' has black or reddish brown gena and parafacials. Also, ''C. mortuorum'' has only one postacrostichal seta, and ''C. cadaverina'' has two. Lastly, ''C. cadaverina'' is much more common throughout North America.

Habitat

''C. mortuorum'' lives on woodland edges, meadows, and other places with flowers in Europe and Asia. It has been found in the northern regions of both Europe and North America, and east to Turkestan.

Also, it can be found in a wide variety of carrion from rotting fish to Arctic vole carcasses. Within England, it has been found mostly in upland areas – above 500 m. In these upland areas, it is mostly found on small carcasses, such as mice and other small mammals; occasionally, it will be found on larger carcasses like sheep.

In the absence of carrion, excrement provides a food source. The adults feed on pollen, and are found from May to September. ''C. mortuorum'' has not been shown to cause myiasis.

As a cold weather fly, it is expected to show up in the fall months. However, one study found the presence of ''C. mortuorum'' on a mouse carcass in mid-August, and on a sheep carcass in mid-June.

Reproduction

The larval stage is broken up into three instars; and, each instar has 12 segments. The first instar is about 1.87 to 2.13 mm in length, and has complete anterior spinal bands on segments 2 through 8 and complete posterior bands on segments 7 through 11. Also, the skeleton of this instar has a lateral plate on which the narrowest portion is smaller than the length of the mouth hook; this is the same for the second instar.

The second instar, however, is 2.74 to 3.75 mm in length, and has complete anterior spinal bands on segments 2 through 9 and complete posterior segments on segments 8 through 11.

Lastly, the third instar has been found to be 13.12 to 14.00 mm in length with complete anterior spinal bands on segments 2 through 8 and complete posterior spinal bands on segments 10 through 11. It can be distinguished from other third instar larvae in that the dorsal margin of its tooth is mostly straight, and then curves suddenly at the tip.