Friday, 30 October 2009

Giant garden spider

Some individual garden spiders, familiarly installed in strategic spots in the garden have disappeared in the last weeks, probably after laying their eggs and spinning a cocoon around them in a safe, dry corner. I came across this magnificent female, going on a walkabout. The largests I've seen (a 1 p coin for comparison).

Thursday, 29 October 2009

Halloween peacock

It has been a very mild Autumn so far. Today, temperatures rose over 15 oC. A butterfly fluttered over my head. I thought it could be a Red Admiral. Fortunately, it settled to sunbathe on a white, south facing wall, and using my camera telephoto I was able to take a picture and identify it as a Peacock. It is the latest active Peacock I have seen since I started to record butterflies in 2003.

This is the usual phenology of Peacocks in my grid square (TA0830). A single brooded species, adults break hibernation in April, breed, and the next generation is on the wing in July. Butterflies usually start hibernation in early September.

Sunday, 18 October 2009

Eyed Beauty

After their slow start this year, Harlequins are around with a vengeance. There are some railings near my local park literally covered on larvae, pupae and adults, presumably all need to emerge as adults before the winter sets. When my daughter came running to show me a ladybird I though it would be another harlequin. But it was instead a very nice surprise: an Eyed Ladybird, Anatis ocellata, the largest ladybird in the UKThis species is associated to conifers and there are not many in the park so it appeared a bit misplaced.
Eyed Ladybird

Monday, 12 October 2009

Window frame spider

Zygiella spinning its web on a garden railing
Suddenly, most of the summer bugs seem to have disappeared to leave your usual autumn suspects: wasps, a few Bombus pascuorum, garden spiders and plenty of flies. There is a common bug, though, that hangs on year round. It is the window frame spider, Zygiella x-notata. This species is an orb spider (related to the Garden Spider, Araneus diadematus) which spins its webs on gates, window frames, wheelie bins and other flat surfaces associated to human constructions. The web is quite recognisable, as it has a sector with no connecting threads in it, it is thought to be adapted to be built in such flat dimensions by keeping the signal thread free from getting tangled in the sticky connecting threads. The signal thread runs in the middle of this sector and allows the spider to detect any vibrations due to insects trapped in it. During the day, the spider hides in a silky tube on a corner, with the first pair of legs touching the signal thread that leads to its web. At night she is often seen either just outside the retreat or on the web, in a more similar way to garden spiders.
A Zygiella x-notata web on a garden gate. The spider's retreat is on the top right-hand corner. Note the signal thread and the 'empty' segment on the orb
This one used to live inside the kitchen window.
Eventually, she laid her eggs and spun a cocoon for them. She sat on the cocoon until she died.

Friday, 9 October 2009

Watch out! Tegenaria males about

It's that time of year again. Come early autumn, large, long-legged, fast spiders take you by surprise crawling across the living room, or alongside skirting boards or, better still, greeting you when you are getting in the bath - where they have fallen the previous night. They are house spiders from the genus Tegenaria. It is not a large genus, with only 11 species in Northern Europe, but they include the largest spider in the UK, the Cardinal spider Tegenaria parietina, which can reach 14 cm across its legs (see the proof here). Tegenaria are remarkably difficult to identify to species level, something I find quite frustrating. Forget about it with the females (unless you capture them and closely examine their genitalia). Even with relatively close shots of male palps identification is difficult. You have to content yourself with Tegenaria sp. Females usually keep to their web on hidden, dusty corners around houses or under beds. The wandering house spiders of the autumn are actually males in search of females.
This one stayed on a skirting board for a whole day a few days ago.
I got a close shot of the palps of this other male, three years ago to the day.

Sunday, 4 October 2009

Small Tortoiseshell butterflies

A couple of weeks ago I did the usual annual compilation for 2009. I have compiled my butterflies records and submitted them to the local Butterfly Conservation recorder since 2003. It has been a super butterfly year. I recorded a total of 17 sp. within the boundaries of the City of Hull. One of the most noticeable species  this year has been the Small Tortoiseshell. This Small Tortoiseshell was the first butterfly I saw this year, after the long, cold winter, sunbathing on the pavement on a busy street.
There has been a lot of talk about the population decrease in this species, possibly due to mortality due a newly arrived parasitoid tachinic fly, Sturmia bella. This fly has been found to parasitise up to 40% of south England Small Tortoiseshell caterpillar clusters. There seem to be additional reasons, as this butterfly shows marked cyclic population fluctuations even before the fly was recorded in the UK.

 The graph above shows the collated results extracted from the UK Butterfly Monitoring Scheme 2007 report (well worth browsing if you like butterflies).
Despite all this, 2009 has been the best Small Tortoiseshell year since I record butterflies.
This is my total year count graph, showing the 'rebound' of the Small Tortortoiseshell after the 2006 'low'.
This is the phenology of this species in Hull.

It seems likely that there are two broods a year.
I discovered a great butterfly site, packed with info and with superb photos: