Small Milkweed Bug Nymphs and Adult

2021 November 28

Now, I am not 100% certain that these are all the same species, since I didn’t actually keep the littlest one and raise it to adulthood. But, I think that it is pretty likely that they are. So, this first little feller was in our house on August 15, 2020:



Then, just about a year later on August 8, 2021, I found this one that looked really similar (but somewhat more mature) crawling on our window screen:


And finally, on October 8, 2021, I found this fully mature, winged specimen on the wall just outside the bathroom:



The partially-exposed wings were as black as black velvet, except for a couple of white spots and a white wing margin.


So anyway, this is an easy ID. They are Small Milkweed Bugs, Lygaeus kalmii. As you might guess from the name, they primarily feed on milkweed juices, particularly the juices from the developing seeds. Although, it is reported that they will also scavenge dead insects, and even prey on live insects, particularly early in the spring when the milkweed is scarce. They have several generations per year and overwinter as adults, which is why I was able to find both extremely young and partially grown nymphs at the same time of year.

And, the reason I kept finding them in the house is because we have milkweed planted all around the house and yard for the monarchs[1]. There are a bunch of milkweed plants right by the back door, and I expect these bugs sneak in pretty regularly when we come and go through the door.

According to BugGuide, the eastern strain of these bugs has pretty much completely black hindwings, while the western strain has large white spots and a pronounced white margin on the wings. Since this one has small white spots and a moderate white margin, it looks like our local strain is about halfway between the eastern and western strains.

[1] Incidentally, on the one hand the milkweed is in fact very effective for attracting Monarch butterflies, and giving them a place to raise their caterpillars. The downside is that there is a reason why it is called milkweed. Now that it is established, it is a lot of effort to remove if we decide it is growing in a place we don’t want. It comes up from even the smallest scrap of root. And, once it comes up, it gets monarch eggs on it right away, and we can’t bring ourselves to root it back out until the monarch caterpillars are done with it.

One Response
  1. December 13, 2021

    So that’s what those are! In the spring, the ground at the Fiesta Island dog park is crawling with them. I had been informed they were lady bug larvae, but that ID looks solid.

    Thanks for the tip.

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