They are called aphid midge and their larvae look like golden yellow maggots wallowing in the middle of an aphid infestation.
https://www.omafra.gov.on.ca/IPM/english ... idges.htmlAphid midge larvae are an important natural enemy of aphids, attacking more than 60 different species. Larvae paralyze aphid by attacking their leg joints, and then sucks them dry, leaving a blackened, collapsed aphid attached to the leaf.