Wednesday, 4 May 2011

Four wings good?

I usually associate the first damselflies of the year with fern fronds, because they use them as perches to sun themselves and as launching pads for a leap to catch their prey. This year, however, the ferns are still unfurling and the damsels are having to resort to Bramble for resting on. This is a female Large Red Damselfly:

Female Large Red Damselfly

The standard definition of Diptera, or flies, is that they have only two wings. This is true, but only to a certain extent. Flies do indeed have only two wings in the conventional sense, but they also have two modified wings: the halteres. This shot shows the two halteres - located just behind the large, main wings - of a Cranefly:

Halteres of Cranefly
The halteres vibrate at roughly 45 degrees from the axis of the fly, but at 90 degrees to each other. Due to the coriolis effect, they act as gyroscopes and transmit information about rotation to help the fly to stabilise during manoeuvres. Bees, wasps, butterflies, moths, dragonflies and many other insects have 4 wings, but flies generally have more manoeuvering and hovering capability due to their combination of two wings with two halteres.

When I'm looking for moths at night, I often find other insects attracted to the light. This Cockchafer was hanging on my wall last night:

Cockchafer beetle
The Cockchafer has a very interesting lifecycle: the larvae live underground for three or four years, and the adults tend to be seen more frequently in three or four year cycles. There appears to be another cycle of perhaps 30 years, when the beetles are seen in huge numbers. The specimen in the picture above appears to have lost its right antenna.

The micromoth in the next shot has a glorious name: Schreckensteinia festaliella


This moth always lands with its middle legs outstretched and pointing upwards. I suppose with all those spikes, it must be the only safe place to put them.

As I have mentioned before (and will doubtless mention again), Pug moths are rather difficult to identify to species. The Foxglove Pug can be separated from the very similar Toadflax Pug by the 'notch' in the outer edge of the dark bar, as indicated by the arrow: 
Foxglove Pug, showing notch in wing bar
Size and timings are also different between the two species, but without a comparison, and given the very early season we're having, we have to act on the clues we are left with.


3 comments:

The Weaver of Grass said...

Lovely photographs, Stuart.
When we were at the gravel pits yesterday (see my blog for yesterday) there were a lot of what looked like little dragon flies whizzing about - the air was full of them.

Emma Springfield said...

You packed a lot of information in with your lovely pictures. I enjoyed the whole thing.

RBr said...

Thanks for the informative post, and 1st rate pictures.