Didea

Distinguished from other hoverfly genera by the combination of: large, broad, flat, and strongly emarginated abdomen with narrowly divided pale bands; black scutum that is shining or subshining; anterior anepisternum bare; upper and lower katepisternal hair patches broadly separated; meron bare; metepisternum and metasternum with some hairs; several hairs at the posteromedial apical angle of the hind coxa. The moderately dipped R 4+5 vein and sparse lower calypter hairs provide additional diagnostic characters.

Large, robust hoverflies 10–15 mm in length. Abdomen is broad, flat, and strongly emarginated with narrowly divided yellow, yellow-green, or pale green bands. Scutum is black, either shining or subshining. Notopleural callus and postsutural scutal margin may be obscurely yellowish in some specimens. Pleura is black with densely pale-pruinose areas on the upper half. Ventral scutellar fringe is short and sparse. R 4+5 vein is moderately dipped into cell r4+5. Lower calypter has very few fine, pale, erect, scattered hairs on the upper surface.

Associated with arboreal environments, reflecting larval dependence on aphid colonies in trees.

Holarctic distribution, occurring in the Nearctic and Palearctic regions. Documented from North America (including Vermont), Denmark, Norway, and Sweden.

Flight periods occur late in the year; adults are active primarily in late summer and autumn.

Larvae are predators of arboreal aphids, contributing to natural biological control of aphid populations in tree canopies.

• SyrphusSimilar black and yellow banded coloration, but Didea is distinguished by larger size, broader and more strongly emarginated abdomen, and specific thoracic hair patterns including bare meron and separated katepisternal hair patches.
• EpistropheShares yellow-banded abdominal pattern and Syrphini tribe membership, but Didea differs in abdominal shape (broad, flat, emarginated versus more rounded) and in details of thoracic pilosity and wing venation.

• hoverfly
• predatory larvae
• aphid predator
• late season
• Holarctic

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• NOMENCLATURAL NOTES ON NEARCTIC SYRPHINAE, WITH DESCRIPTIONS OF NEW SPECIES OF SYRPHUS AND KEYS TO NEARCTIC SPECIES OF DIDEA, EPISTROPHE S. STR., AND SYRPHUS (DIPTERA: SYRPHIDAE)