Sunday, 1 October 2017

Arachnids, Butterflies and Crickets

The year is zooming along and it's October already! How did that happen?

I'll start today with a red admiral from last week. Despite the temperatures gradually dropping there are still plenty of these hardy butterflies around.

The results of Butterfly Conservation's Big Butterfly Count were released this week and it was good news for red admirals. Despite the wet summer numbers have risen by 75% compared to 2016. A few decades ago Red Admirals were only summer visitors to the UK- they arrived from warmer parts of Europe in the Spring, bred here and their offspring flew South. Now many overwinter in the UK and the Red Admiral is the most commonly recorded butterfly during the Winter. 

The most commonly spotted butterfly of the count was the gatekeeper and other butterflies which had a better 2017 than 2016 include the comma, the small copper and the common blue. But it was a terrible year for the UK's three species of white butterfly (green-veined white, large white and small white) with all showing amongst their lowest ever totals of the count. This is partly due to the wet summer but may also be because they emerged earlier than usual, before the count begun. Certainly it felt like they were around in large numbers locally. 

Moving on, it's always nice when a more unusual moth finds it's way into the house where you can get a good look at it. This is a light emerald moth

These are relatively common moths which can often be seen in gardens and parks. It's likely this individual is from the second of two generations this year. The green colour fades over time until the moth eventually becomes almost pure white- this is common amongst green moths. 

I've noticed lots more spiders over the last few weeks, many obstructing pathways with their webs. 

These are both garden spiders, easily identifiable due to the cross of white spots on the abdomen. Spiders catch their prey in a variety of ways but this species does so in the one most familiar to us- they spin orb webs and sit in the middle of them waiting for insects to fly into the web. 

Spider webs are incredible feats of nature. The tensile strength of spider silk is greater than the same weight of steel and has much greater elasticity. It's also thought that webs are electrically conductive which causes the silk threads to spring out to trap their quarry- flying insects tend to gain a static charge which attracts the silk.

Another recent invertebrate sighting was this cricket which I think is a roesel's bush cricket

Interestingly, a small number of this species are 'macropterous' which means they have much larger wings than normal. In most populations it's about 1% of individuals but some populations have higher numbers. It's thought that this is a dispersal technique. The idea is that in well-established populations or in strong seasons the population becomes dense so macropterous crickets can fly further to an area where there are less crickets and therefore more food. 

That's all for today but I'll leave you with the bright red leaves I always love to see at this time of year at the corner of my street. 

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