Recently, I came across three small beetles on a blade of grass near the Jette Trail. As often happens, I took lots of pictures, but when I got home and had a chance to really look at them, I wished I’d taken more. It turns out this little blue beetle is a rarity.
Zooming in on them at home, I could see the pock-marked, ridged outer wings and the non-standard antennae, which are flattened and enlarged toward the ends, and positioned in front of the head.
Until I submitted this image, Anisostena californica hadn’t been recorded in Oregon on BugGuide.net. Scientifically, they’re in the Leaf Beetle family and the Hispine beetle sub-family. Hispines like this one are leaf miners, which means the larvae tunnel inside leaves. Yes, it’s a whole new world at the macro scale.
There’s scant information about these beetles online. One 1982 research paper on a different, eastern U.S. species found adults on something called “panic” grass (genus Panicum). Later, they found larvae and pupae living comfortably in tunnels inside the same grass. It’s mind boggling to think an animal species can spend its entire existence in an area the size of a clump of grass. It reminds me of the Dr. Seuss story Horton Hears a Who.
The authors note that the beetles are scarce in their known distribution areas. That, and the fact they are so small and could be mistaken for any number of other tiny dark insects … make it easy to see why they play a good game of hide and seek.
Two of the beetles I saw were mating, and the third was hanging around nearby. I’d guess it was another male, hoping to appeal to the female in case it didn’t work out with beetle #1. In any case, they were increasing the likelihood there will be more Anisostena at Mount Pisgah in the future.
A second research article I came across (see below) revises the descriptions of the genus. It lists Oregon as a location where Anisostena californica was found, and says the host plant is “unknown.” I doubt I can find them again, but if someone found their larvae living in the grasses, we could add something to the scientific record.
Stay curious!
See more of Karen’s work here.
Sources:
1982 research paper from the Coleopterists Bulletin: https://www.jstor.org/stable/4008050. Accessed 5/24/23.
1994 paper on the re-categorization of the Anisostena genus: https://core.ac.uk/download/pdf/14514962.pdf. Accessed 5/24/23.
