I finally picked up the pencils again this past weekend and started drawing again for the first time since October. I was a little worried that I’d have lost my touch, but this drawing of the dark form of the Margined Lady Beetle (Exochomus marginipennis) turned out so well, I realized I’d have to redraw my old Exochomus illustrations to keep up with it!
This species is highly variable, and while this dark form is the most common, it can also have the dark areas broken into spots. A pale form with only two spots occurs along the Gulf Coast and in Texas.
The other Exochomus in eastern North America is the nominate subspecies of Children’s Lady Beetle (Exochomus childreni childreni). I admit the common name sounds a little odd, but it isn’t related to young people; it honors the British naturalist John George Children (1777-1852), the founding president of the Royal Entomological Society of London. The typical form of this species strongly resembles the pale form of the Margined Lady Beetle, but notice the entirely black pronotum and the additional spot at the rear of the body.
Just to complicate matters a little more, Children’s Lady Beetle can also vary in pattern, with a dark form resembling the typical form of the Margined Lady Beetle. However, the dark areas are smaller and more narrowly-connected, and again the pronotum is entirely black.
In most of eastern North America, the only species of Exochomus is the Margined Lady Beetle; you only have to worry about telling it apart from Children’s Lady Beetle in Florida. (On the western Gulf Coast and in Texas, there’s the other subspecies to worry about, Exochomus childreni guexi; it looks much more like the Margined Lady Beetle, with pale markings on the pronotum. I’ll tackle that one in my next field guide!)
Genus Exochomus is in subfamily Chilocorinae, and like most of the subfamily it primarily feeds on scale insects. However, it will also consume aphids. The habitat of these beetles is poorly known; scale feeders may occur mainly on trees, while aphid feeders may visit low herbacious plants. The only one I’ve encountered was a larva of Exochomus childreni guexi eating aphids on a milkweed vine twined around tall grass at the edge of a river, and I was able to raise the larva to adulthood on another species of aphid. This may not be typical for the species or genus as a whole, but it does offer some idea of where to look for them!