The Bigg Bird Forum

[Martin]

these two types of caterpillar (or moth?) are destroying the leaves of a 4ft hazelnut sapling; one of them has a strange black appendage(?) on it's back !

does anyone know what they are and is it possible to transfer these to my nettle patch without affecting them - thanks

caterpillar unknown 1
Poster: Martin, viewed 92 Time(s)

unknown with strange appendage
Poster: Martin, viewed 107 Time(s)

[mybitoftheplanet]

Hello Martin,

They are very clear photographs.

The first one isn't a caterpillar but a sawfly larva, in a tail-up posture that it adopts when disturbed. You can tell that it isn't a caterpillar because it has more than five pairs of stubby prolegs behind the three pairs of true legs. Caterpillars will have five or less pairs of prolegs (including the specialised pair of claspers right at the tail end of the body.

I can't be sure but it could be the Hazel Sawfly (Croesus septentrionalis). Despite its name it also lives on Alder and Hazel and usually move around leaves as a group. I don't think that it would be happy on a nettle. I can understand how you would be concerned about this little beast. I get them on my Birch tree and when a group of them encircle the rim of a leaf and start eating the leaf does not last long.

The hairy one is a caterpillar, probably a moth called a Grey Dagger(Acronicta psi). It's a common species and its caterpillars feed on a wide range of deciduous trees and shrubs. Again, I don't think than nettle is on its favourite food list, but other deciduous plants in your garden should be fine.

[Martin]

David - thankyou very much indeed for the id's and subsequent useful info - highly informative ! I spent ages searching caterpillar websites and just couldn't find these beasties. The sawfly larvae are absolutely stripping my young hazel, probably 2/3rds of the leaves have been munched away. I've also got a nearby young birch tree which is looking a bit worse for wear. The 'grey dagger' is probably the most exotic looking thing I've ever seen in the garden, and I'm not sure what that appendage is for - defence against swallowing by birds perhaps?

photos were taken with my favourite lens - a Sigma 105 macro, the original shots fill the frame at just over 3K horizontal resolution, but I resized to 500 for the forum

thanks again !

[mybitoftheplanet]

I can understand how you feel - when my Birch was small I had a similar situation, but it's now >30ft high and very healthy despite annual visits from the sawflies! This year the group of larvae that I was monitoring all disappeared within a day, probably because the local Blue/Great Tits found them.

While the web is very useful it still has a long way to go before it is a good assistant when you want to identify something. Unfortunately, most of the sites that catalogue insects tend to work the wrong way round. Either you need to already know the species name before you can see images, or you must spend perhaps hours looking through them. Those that do use keys inevitably require you to have specialised knowledge of the insect group, and they assume that you have a microscope and a dead insect to examine.

I don't claim to have the specialised knowledge, but I do have a bookshelf next to my computer and I use the guides that I've picked up over the years to give me a starting point. Mind you, unless you wish to spend a fortune on the specialist books (which I haven't) you have to be extremely wary of books that claim to be 'The Complete Guide to .....'!

The book that I have to help with caterpillars is the 'Collins Field Guide to Caterpillars of Britain and Europe'. You can see the illustrations of you go to

http://www.whatsthiscaterpillar.co.uk/plates.htm

It is based on drawings rather than photographs which isn't a bad thing, and the book groups the caterpillars according to their main food plants. Once I find a close match then I carry out a Google search to find other references.

To confirm your thoughts, the book suggests that the spikes that some caterpillars have may help make the caterpillar appear bigger and helps make them more difficult fot small birds to swallow. The hairs also help to make the caterpillar unpalatable.

A decent macro lens is a pleasure to use - I have one on my 5D almost permanently!

[Martin]

That book looks like an excellent place to start, using pictures and illustrations rather than trying to second-guess what it's name might be, so I will definitely put that on my 'wanted' list; fortunately there are people like your good self to help out complete novices.

I will allow the sawflies to chomp away at my hazel, and hope for the best, or else call in blue tit reinforcements!

despite technology advancing I'm still using an 'adequate' D50; I'm very much enjoying macro, there's always something interesting to shoot every couple of feet (unlike telephoto..)

regards