Last week I gave you this (somewhat dusty) mystery object to try your hand at identifying:

I know that insects aren’t a frequent occurence on the blog, so this was a bit of an unfamiliar one for many of the regular Zygoma commenters. Of course, that didn’t prevent some astute observations.

Chris Jarvis immediately spotted that this is a wood wasp or sawfly, while palfreyman1414 flagged that it looks more like a fly (barring the long ovipositor). That’s because wood wasps, despite being members of the Hymenoptera, lack that characteristic wasp-waist that makes the Apocrita (the hymenopteran Suborder containing wasps, bees and ants) so distinctive.

The Symphyta is the Suborder containing the sawflies and there are thousands of different species. However, narrowing it down wasn’t really that hard, since sawflies specialise in using their ovipositor to lay eggs in the stem of quite specific host plants and the only sawflies in this size range are in the family Siricidae, which are the ones that pick on trees (which is pretty interesting, since they form a symbiotic relationship with wood-digesting fungi in order to feed on wood as larvae).

Of course, being insects, there are still around 150 to choose from, but between ruling out taxa that have adopted Batesian mimicry and those that are a very different size or shape, it becomes easier to narrow down the possible contenders – especially when you consider that this one turned up in Dublin, Ireland (although as pests of wood they can emerge from pine timbers a long way away from their point of origin – this one probably got into the Dead Zoo in some of the timber being used for our big decant project). The best fit for this specimen lies in the Genus Sirex.

When tryingto to distinguish between members of Sirex it’s important to pay attention to colour details of the legs and antennae. In this case it has red legs and black-and-red antennae. If you spend a while checking through the very helpful Sawfly GenUS resource you’ll find that the best fit for the mystery specimen is a female Sirex juvencus (Linnaeus, 1758).

Of course, the entomologists out there managed to figure all this out without any problems, both on Twitter and in the comments.

Siricidae woodwasp, Sirex sp. All tarsal segment 5 look yellowish, so I presume S. Juvencus, should be black in noctilio?

— Jaswinder Boparai (@jaswboparai) June 25, 2021

So well done to Jaswinder and Russell Stebbings for getting a species level identification – I would say that you got it right, but since I’m not an entomologist I think I should just be pleased that your more informed opinions happen to support my best guess. Thanks!

Stay tuned for another mystery object next Friday. Have a great weekend everybody!

*not a Bug – the True Bugs are Hemiptera and have nothing to do with this.