The wasps are Encarsia formosa, or something very much like them.
These critters have a very lopsided distribution of genders in their populations.
https://entnemdept.ufl.edu/Creatures/BE ... ormosa.htm writes that:
Among the several hundred wasps that emerged from pupae I had in plastic containers, I saw two males. At least, there were two slightly smaller wasps, all black, that I saw courting the larger black-and-yellow ones, albeit with no success that I could see.Encarsia formosa is a thelytokous species, where females develop from unfertilized eggs. Males exist but are rare and emerge concurrently with their female counterparts as primary parasitoids. Thelytoky in E. formosa is mediated by Wolbachia (a genus of sex-determining intracellular bacteria) infections, and while E. formosa exhibits mating behavior and males produce sperm, females are unable to be properly inseminated and thus cannot reproduce sexually (Zchori-Fein et al. 1992). Females are typically ~0.6 mm long by 0.3 mm wide, with a black head and thorax and a yellow abdomen (Fig. 1). Males are dark in color and may also occur rarely as autoparasites (parasitic on their own species) of female Encarsia formosa larvae (Gerling 1966).
I got only one picture of a live male, shot by cell phone through the eyepiece of a dissecting scope, looking through the flat wall of a plastic container:
Here is a quite more clinical view, following the untimely end of its probably frustrating life.
For reference, here is a female at same scale:
These latter images were with Mitutoyo M Plan Apo 10X NA 0.28, focus stepped at 0.005 mm.
The male was photographed lying on a neutral gray card. I avoided fastening it to any handle because I wanted to preserve it in alcohol after photographing. I tried to photograph a female just the same way, but all those specimens had postures that would not let them lie stably on their sides. After several frustrating iterations of lining up a shot, only to have the specimen fall over onto its back at the slightest vibration, I gave up and fastened the female to a hair suspended over the card (hence the totally blurred background).