Wednesday, 23 July 2014

Thistle be interesting...

...I hope.

Fine weather tempted me into a walk along Muddy Lane. As I've stated elsewhere its official name is Pit Lane; its proximity to houses and convenience for dog walkers has led to "Dog-poo Alley" being a more appropriate appellation - convenience indeed!

I didn't linger along this lane - bridleway actually - but pushed on to a less noisome area adjacent to Parson's Spinney.

En route I paused only for a less than satisfactory picture of a Shaded Broad-bar, Scotopteryx chenopodiata. Although not strictly a day-flier it is easily disturbed and therefore frequently seen. The larval food plants are clovers and vetches.

Shaded Broad-bar, Pit Lane, Byfield.
21 July, 2014

A plant of Field Scabious, Knautia arvensis, had attracted an empid fly which was probing deep into the flowers for nectar. The species is Empis livida, perhaps the commonest of all the British empids, easily recognised as some of the the radiating wing veins do not reach the wing margin.

Empis livida visiting Field Scabious. Pit Lane,
Byfield, Northants. 21 July, 2014

Next to the Scabious was a rather large clump of Creeping Thistle, Cirsium arvense. It is only too common and thus easily passed by without a second glance. It is "regarded as one of the worst pasture weeds ...with the roots having been found to a depth of 18 feet" (Sir Edward Salisbury, "Weeds and Aliens", Collins New Naturalist Series) and is very difficult to control. Tell the insects it's a problem; they visit the flowers in great numbers.

Phytomyza cirsii mining the leaves of Creeping Thistle
Trackside west of Byfield.  21 July, 2014

Most insects are there for the nectar, but not all. Larvae of the fly, Phytomyza cirsii, are busy mining the leaves. The insect does little damage and farmers might wish it were more injurious. The larvae eventually drop to the soil to pupate.

I spent some thirty minutes beside the thistles, inevitably getting pricked by the sharp spines and, by way of variation, being bitten by clegs, in this case female Notch-horned Clegs. I was happy to put up with these minor discomforts in order to take a few photographs - all of commonplace insects but none the less interesting.

Dingy Footman? Trackside west of Byfield.
21 July, 2014

A moth fluttered down from a thistle head and obligingly settled on my net. It is, I believe, a Dingy Footman, Eilema griseola. This group of moths can be tricky but I had no wish to capture the specimen even though that would have allowed a positive identification.

A common tachinid fly, Eriothrix rufomaculata, beside
a track west of Byfield. 21 July, 2014
With bright red flanks to its abdomen the tachinid fly, Eriothrix rufomaculata is very distinctive (although a few other tachinids have similar red patches). Tachinid flies are parasites, their larvae feeding on other living insects, known as hosts. The hosts usually die a grisly death although there are cases where this seems not to happen. For a long time the host species of E. maculata was a mystery but in 2009 a paper was published* showing that a pyralid moth, the Garden Grass-veneer was one unfortunate victim, but there are likely to be others.

Rutpela maculata visiting Creeping Thistle.
Byfield, 21 July, 2014

Next up was a longhorn beetle, Rutpela maculata. This striking insect is very common in England and Wales but there are only a handful of records from Scotland. Why the striking colours? Is it to vaguely mimic a wasp? If so, it isn't very convincing. Perhaps it has a foul taste which a would-be predator wouldn't forget in a hurry.

 Oedemera nobilis: a male feeding on Creeping Thistle

Another common beetle, Oedomera nobilis was present. Its thighs (technically known as femora) suggest lots of hard work in the gym! In fact, the swollen femora show that it is a male. A curious feature of this insect is that the elytra (wing-cases) always gape. 
Helophilus pendulus. Trackside west of Byfield, Northants
21 July, 2014

A smart hoverfly added to the variety. It was a female Helophilus pendulus. "Helophilus" means "sun lover" so it should have found the conditions to its liking. 

Green-veined White. West of Byfield.
21 July, 2014

Butterflies were there a-plenty. This is the green-veined White, Artogeia napi. Like many of its close relatives it feeds on members of the Brassica Family but apparently is not often found on cultivated plants.

Terellia tussilaginis nectaring at Creeping Thistle.
Trackside near Byfield,  21 July, 2014

Members of the Tephritidae family are "picture-winged flies", that is, their wings are patterned, often with stripes. This one is Terellia tussilaginis, a frequently-encountered species. It is commonly associated with burdocks (Arctium species) and there was indeed a clump of burdock nearby.

Small Skipper, Thymelicus silvestris, nectaring on Creeping Thistle, west of Byfield. 21 July, 2014

A Small Skipper also called in. I have reproduced the picture in a large format so that the antennae are visible. It can be seen that the underside of the tip is yellow, thus distinguishing if from the Essex Skipper, where the underside is black.

A pair of Black-tipped Solder Beetles, Rhagonycha fulva and a
Seven-spot Ladybird, Coccinella 7-punctata.

A final picture. Here a pair of Black-tipped Soldier Beetles, Rhagonycha fulva, are attempting to mate. A Seven-spot Ladybird observes carefully. It will award points for degree of difficulty, style and so on.

So, with a few cleg bites to show for my efforts, I called it a day. No rarities, in fact not even a scarce insect, but nonetheless satisfying.

e-mail to Tony White:

* Stuart Paston and Graham Rotheray writing in Dipterists Digest, 2009 (16,1)

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