The white-crossed seed bug (Neacoryphus bicrucis), like a lot of true bugs, lives through the winter as an adult and this one, at least, was living at Mount Pisgah last week. Where it spends the rest of the year is anyone’s guess.
A study from the state of Georgia in the 1970s found that Neacoryphus bicrucis migrates, “often at great altitudes,” to track the development of its food source, ragwort seeds. I didn’t pay the $40 to see if the paper defines “great altitude.” I’d be interested to know if that means 50 feet, or 500, or more?
Interestingly, when females don’t have enough food to sustain them, or enough mates, they fly to a better location. But females lose their ability to fly when there’s enough food.
The reason is that flight muscles take up space in the bug’s body, and they also use lots of energy. In fact, females don’t even develop ovaries until they’ve flown from their overwintering site to a spring location. When they need energy to make eggs, hormones trigger the flight muscles to shut down. Females lay about 140 eggs over a six-week period, with older and more well-fed females producing more eggs.
Males, mostly, maintain the ability to fly throughout their adult lives.
Bright colors on insects usually signal either that they’re dangerous to eat, or they want you to think they’re dangerous to eat. Neacoryphus bicrucis isn’t fooling about being distasteful. They take on poisonous alkaloids from ragwort which is a plant, by the way, that can cause liver failure in horses and cows.
See more of Karen’s work here.
Solbreck and Pehrson’s 1979 paper on migration: https://pubmed.ncbi.nlm.nih.gov/28309827/. Accessed 1/24/22.
An awesome Canadian summary of seed bugs: http://biologicalsurvey.ca/ejournal/ls_34/ls_34.pdf. Accessed 1/24/22.