A Weakness for Weevils

I was excited to find a new weevil on our property the other day. At least until I identified it.

Meet Otiorhynchus sulcatus—the black vine beetle—pest on a wide range of garden plants, including grapes, black currants and strawberries (all common in my garden).

I admit, I have a weakness for weevils—no matter how much of a pest they are, I think they’re cute. And this one is no exception. She’s lovely, in spite of her diet. And I’m certain she’s a ‘she’, because no males of this species have ever been found. The black vine beetle reproduces parthenogenetically, producing viable eggs without the need for fertilisation by males. 

This ability is the result of a bacterial symbiont in the genus Wolbachia. When researchers in California eliminated Wolbachia in black vine beetles (by giving the beetles antibiotics), the beetles’ unfertilised eggs were no longer viable. It’s a clever little ploy by the bacterium to ensure its own reproduction—only infected insects can reproduce, and they can do so without the trouble of finding a mate (I wrote more about this fascinating relationship in Putting the Science in Fiction and on Dan Koboldt’s Science in Fiction blog).

Another cool feature of the black vine beetle is that it is flightless. It’s not uncommon to find flightless insects and birds here in New Zealand, but it’s a little unusual to see it in invasive pests like the black vine beetle. Native to Europe, the black vine beetle is now distributed all around the world. Pretty impressive travelling for a 6 mm-long flightless insect.

Apparently black vine beetles can cause significant damage to plants. The larvae eat roots in the soil and do the most damage, particularly in potted plants, where root growth is limited. I’ve decided not to worry about them at the moment. I’ve got more damaging pests to worry about, and to be honest, I wouldn’t mind seeing them again. They are awfully cute.