Tuesday, 14 June 2011

Making hay

Two posts in two days!

The first two shots show the larval case of the micromoth Coleophora serratella on Alder. 

The larva cuts out part of the leaf and rolls it up into a cigar shape, changing the case a couple of times as it grows. The cutouts can be seen at the lower edge of the leaf, with the case towards the top of the leaf:

Larval case of micromoth Coleophora serratella
The larva moves slowly over the surface, grazing as it grows and eventually pupates, still inside the case.
Coleophora serratella on Alder
This is really just a form of leaf-mining, but it allows the moth to grow larger than it could if it was constricted to living inside the tight confines of the leaf. There are quite a few different Coleophora species, each mining different groups of plants from trees through shrubs to clovers. The clover one is particularly well-hidden as it uses one of the flowers as a case and then hides amongst the other flowers. I have looked in vain for those, but maybe they're too well-hidden.

Marsh Cinquefoil has to be one of our most easily-recognisable flowers, although I think it's rather scarce: I have only ever found it in two locations. There are a few specimens between the edge of a bog and a stream which runs along the hedgerow at this point:

Marsh Cinquefoil

The hoverfly Rhingia campestris has an extremely long tongue (arrowed) which enables it to reach nectar that other insects cannot reach.
The hoverfly Rhingia campestris on Raspberry
The tongue is so long that it needs to be folded up for storage when not in use, which leads to the very unusual 'snout' that can clearly be seen in this shot:

Rhingia campestris, showing 'snout' for storing the tongue

Rhingia campestris is a hoverfly that has been increasing its range in the past few years. It used be seen relatively close to farms, and the larvae are known to live in cattle dung, but the hoverfly can now be found far from agricultural areas. Perhaps it has started to use other sources of food.

There are many leaf miners active at the moment, and I spotted this very common leaf-mining fly Agromyza filipendulae on Meadowsweet:

Leafmining fly Agromyza filipendulae on Meadowsweet
This particular mine was worth showing for several reasons.

1) Notice that the frass (dung) is laid in two parallel lines, along each side of the mine. Many of the leaf mining flies have a very simple scraper to excavate the leaf interior and this only works in a vertical plane. But the leaf is thin and arranged horizontally, so the miner has to lie on its side as it mines. Between each slice, it flips its body through 180 degrees and that points its rear end towards the other side of the mine, leading to two parallel tracks of frass. Other miners (e.g. moths) have more sophisticated chewing mandibles and can mine in one position, leading to a single line of frass down the centre of the mine. The two-track/single-track configuration is one major feature in the identification of leaf miners.

2) The mine has changed at the point arrowed: the frass becomes confused and the larva has changed from green to a dark colour, so I'm pretty sure the larva has been parasitised at the point marked. I rather suspect we're going to find an Ichneumonid emerging instead of a fly.

3) There is a minute (1-2mm) Owl Midge at the lower right hand corner of the picture.

Of all the species that I study and photograph, I continue to find moths the most difficult to identify: the variation within species can be staggering and the similarity between different species compounds this. And that's not counting in the variation due to wear and tear. You need to learn the crucial separating features to be sure: merely looking at pictures won't always help.

The Mottled Beauty can be identified from other Beauty species by the curved black crescent at the end of the black cross-line, marked below:

Mottled Beauty moth
Mottled Beauty is a true polyphage, feeding on many trees, shrubs and flowers.

1 comment:

Emma Springfield said...

I cannot wait to tell my grandchildren that I learned about leaf mining today.