UKNatureBlog

Regular correspondent Bob has another teaser for you. What is this caterpillar? He'd really like to know. Answers on a postcard please. Or a comment, or a tweet, or an email. Thanks!

Update: @Max_Wildlife on Twitter responds with typical speed to suggest it is the caterpillar of the Old lady moth but comments that he'd be surer if he knew what plant it had been found on. I'll ask Bob…

Update 2: Bob says he found it on Swiss Chard (as per the first photo). John's comment below wonders if it is a Large yellow underwing moth caterpillar. For Bob's sake I hope not, as it is described as "one of the most hated of garden pests".

Update 3: Max has refined his opinion and now almost agrees with John – but reckons it's a Lesser yellow underwing. The crucial difference seems to be that the Lesser feeds on foliage (like Bob's Swiss Chard) whereas the Large eats through the base of herbaceous plants and hence is known as a cutworm. Personally I'm going to go with Lesser and call it case closed.

Here is a rather poor photo of a Walnut orb weaver, shot on an iPhone and focussed badly I'm afraid. But it does just about convey the incredible flatness of this example, which I can confirm was alive and to my knowledge hadn't simply been crushed. It seemed to be only a few millimetres thick and notably flatter than others I have seen. Maybe it just hasn't eaten in a while.

A bit of reading suggests that they have muscles in their abdomen that can flatten it at will (the muscles being attached to the dimples on the top of the abdomen) though I didn't find a very clear description of this ability. I wonder if that patch of silk beneath it, caught in the glare of the LED flash, is an egg sac?

Here is a much better picture that I took of one a couple of years back, which I blogged about at the time. You can see that it does have a rather flat abdomen, that being a defining feature. I also ran into loads of them in a pedestrian tunnel once where they really played up to their sinister appearance.

This little beetle landed on my red fleece and I was just quick enough to get a picture. You can see it has just landed as its wings are still poking out from under the wing cases at the back. It's black with four red/orange spots and is a a Four-spotted sap beetle, also known as a picnic beetle.

It earns that nickname owing to its preference for liquids such as beer, vinegar, fruit juice and similar, apparently causing it to ruin picnics by landing in them. I can't say I've ever seen that happen myself though and don't recall ever seeing this sort of beetle until now.

Bob emailed in asking for help identifying this mystery butterfly, which he can't find in his books. My best guess (from consulting ukbutterflies.co.uk's page on Whites) is that it's a Small White (male) that being the closest match I can see. It's sort of a cross between that and a Black-veined White. I'm a long way from sure however and I suspect there are knowledgeable people out there that can supply a swift and clear resolution. So please leave a comment here, tweet, or email if you know.

Update: Thanks to @BC_Suffolk and @SuffolkNature who both responded very speedily via Twitter to identify it as a Green-veined White. Apparently Suffolk folk are particularly hot on their butterflies! What threw me off the scent is that on that favourite reference page of mine the male is pictured with no spots and the female two spots, whereas there's very clearly one spot in the picture above. However plenty of other sources show the male with one spot, e.g. courtesy of Keele University Arboretum.