Milkweed Bugs

A female milkweed bug (Lygaeidae: Oncopeltus fasciatus)

I love Texas–when I’m not complaining about the heat–because you can find insects virtually year round.  In December I was playing with earwigs and now it’s January and already the fire ant mounds are popping up everywhere like spring flowers.  (Working with fire ants has severely warped my perceptions of this event.)  I found this large milkweed bug (Oncopeltus fasciatus) sunning itself today in the balmy 70 degree weather.  Bugguide.com lists these fellows as active only from May to October, at least in North Carolina, which is apparently because North Carolinians have an odd phenomenon known as ‘seasons.’

Ventral view of a female milkweed bug (Lygaeidae).

Milkweed bugs belong to the true bug family Lygaeidae, the seed bugs.  Like other members of the family, milkweed bugs make their living feeding on nutrient rich plant seeds, in this case usually the seeds of the eponymous milkweed plant.  (Yes, this entire previous sentence was an excuse for me to use the word ‘eponymous’.)  They use their tubular mouthparts to pierce the walls of seed pods, feeding on the seeds within.

Like that other famous milkweed feeder, the monarch butterfly, the bright, warning coloration of milkweed bugs warns predators that these bugs sequester toxic compounds from the plant in their bodies, making them distasteful.  Milkweed bugs can be fed a variety of other seeds, although interestingly they habituate to food types and it often takes several generations for them to make a switch.  Milkweed bugs in the lab are generally fed sunflower seeds, shelled or cracked since their mouthparts can’t pierce the harder husks.