The Steely-blue Wood Wasp

Here's a little monster from the garden.  It is a female Steely-blue Wood Wasp (Sirex juvencus), not a wasp at all but a sawfly.  I saw it on the garage wall and dashed for a camera.  It stayed for minute or so before flying off and I managed just these few photos.  I recognised it as a wood wasp but it was identified by Andy Musgrove on the British and Irish Sawflies Facebook page.

This one is 32mm long (the cement in the top photo is 29mm wide).  At first glance I thought it might be a giant horntail, Urocerus gigas, an even bigger species that I have long wanted to photograph, but it wasn't big enough and had no yellow on the abdomen.  A giant horntail once landed on my camera strap in the woods in Cragside, then flew onto my leg before flying off so I didn't get the picture.  Maybe one day.

The steely-blue wood wasp is still an impressive beast.  It has no sting but the spike at the back is an ovipositor for laying eggs in coniferous trees, mostly in damaged or dying timber.  The larvae chew tunnels in the wood for two years before emerging as new adults.

I am not sure how sawfly records are collated but my guess is that Sirex juvencus isn't common.  The Sawflies (Symphyta) of Britain and Ireland website describes it as "common" but quotes the NBN Atlas which has 28 records since 1987.

iRecord has seven records since 2000 (including mine in red at the top).  Verified iRecord data are fed through to the NBN Atlas so these six blue records are also in the map above.

Steven Falk describes Sirex juvencus as "not native to Britain but established in scattered locations".  He calls it the Pale-horned Blue Horntail, a name I haven't found elsewhere.

Sawflies are related to wasps, bees and ants but lack a wasp waist.  There are 8000 species in 800 genera world wide - we have about 500 species in 100 genera.  Adults range in length from 2 to 55mm and the larvae resemble caterpillars.  The most common species in my garden are those that eat my gooseberries (Gooseberry Sawfly) and my Solomon's seal (Solomon's Seal Sawfly).  Perhaps the Steely-blue Wood Wasp laid its eggs in my dead sycamores and I might see some more in two years' time.