2024 December 18

Jeremy Tatum writes:  I visited Goldstream Park today, to see if I could find some female winter moths and if I could tell the difference between the flightless females of Operophtera brumata and O. occidentalis.

   There were lots of adult males of both species.  Females were more difficult to find – they do not fly to lights, of course.

I found the insect below, and I could see immediately that it was different from female O. brumata, so I was quite excited, thinking that it must be O. occidentalis.  It wasn’t until I got home and saw it on the computer screen that I saw that it wasn’t a moth at all – it was a small beetle.  Scott Gilmore kindly identified it as Plectrura spinicauda.

 Plectrura spinicauda  (Col.: Cerambycidae)   Jeremy Tatum

  I did, however, manage to photograph a genuine female Operophtera, which I think is highly probably O. occidentalis (photograph below), If you compare it with a known female brumata (see Invert Alert for 2023 November 22), you’ll see that the wing-stubs of this moth are much smaller than those of brumata.
Wing-stub size may be a reliable way of distinguishing the two species – though more photographs of the female would help to substantiate this.

Believed to be Operophtera occidentalis  (Lep.: Geometridae)   Jeremy Tatum