Friday, 16 August 2013

On the Lookout for Grasshoppers at Noar Hill - 15th August 2013

I had the opportunity to get out of the office yesterday in order to carry out an Orthoptera (Grasshopper and Cricket) survey at The Hampshire and Isle of Wight Wildlife Trusts Noar Hill Reserve. The main purpose of the visit was to check on the status of rufous grasshopper, a species that is known to be present, but had not been searched for recently. It is a species that is restricted to southern England on south-facing slopes of unimproved calcareous grassland, Noar Hill provides the ideal location for the species and has known to be present for many years.

Classic piece of chalk grassland at Noar Hill

The reserve was once the site of medieval chalk workings, but is now owned by the Wildlife Trust. In the spring and early summer it is carpeted with chalk downland flowers, including many species of orchid.

Harebell Campanula rotundifolia

I was hoping for a warm, still and sunny day, since these are the best conditions for Orthoptera surveys. Unfortunately it was quite windy and cloudy, so sunny periods were interspersed will long periods of shade, the temperature dropped considerably during these periods. Over 35 species of butterfly have been recorded at the site, and it wasn't long before we were seeing some of them. Chalkhill Blue was the first species recorded, keeping low in the vegetation but occasionally basking during a sunny interval. This species appears to have had a great year, as on the Wildlife Trusts Arreton Down reserve on the Isle of Wight, a few thousand individuals have been on the wing in recent days. A spectacular sight if you can get there to witness it!

Male Chalkhill Blue Lysandra coridon

Several common blue butterflies were also on the wing, although not as many as there were chalkhills, and the supporting cast included small heath, meadow brown, large and green-veined white and gatekeeper.

Male Common Blue Polyommatus icarus

Hemp-agrimony provided a rich source of nectar for more species, especially peacock, small tortoiseshell and a handful of clouded yellows that were scattered around the site. The latter proved incredibly difficult to photograph as they were easily disturbed, and were being blown around in the gusty conditions.
Peacock Inachis io

Underwing of Peacock Inachis io

Along the woodland edges silver-washed fritillary's, brimstone's and Comma's were also taking advantage of the rich nectar source provided by the hemp-agrimony.

Silver-washed Fritillary Argynnis paphia

Silver-washed Fritillary

Grasshoppers and crickets were proving difficult to locate since they were not really singing in the unfavourable conditions. Dark bush cricket was the first to be heard, and soon meadow, common green and field grasshopper had also been added. Roesel's bush cricket is one of those species which has expanded rapidly since being first recorded in the extreme south-east of the country. A handful of this species were recorded in the areas of taller vegetation, along with a few long-winged coneheads.

Sheltered sunny glade which proved to be a great location for
Rufous Grasshoppers

Eventually, after several hours of searching, a male rufous grasshopper was recorded in a sheltered glade in the east of the site. This species is one of the easier grasshopper species to identify due to the presence of a range of features, some of which are unique and are present on males, females and nymphs.

Male Rufous Grasshopper Gomphocerippus rufus

The grasshopper is generally brown in colour and usually has a reddish abdomen. The male has large club shaped antennae, similar to a butterfly, that are tipped white, these are diagnostic. They do also occur on females and nymphs but are not as pronounced, as can be seen in the pictures below.

Female Rufous Grasshopper

They also have pale palps, which are located by the mouth parts, and the call is like a clockwork toy unwinding. It is a late maturing species and with adults not usually found until late July, but they can survive until late November and even early December.

Rufous Grasshopper - Final instar nymph

Another species restricted to south-facing calcareous slopes in the south of England is stripe-winged grasshopper. It is quite a widespread species and can be quite common in some places. It has a very distinctive call that lasts about 10 to 20 seconds, it is very high pitched, starts with a hiss and then continues with a buzzing, metallic, pulsating sound.

Stripe-winged Grasshopper Stenobothrus lineatus

One distinctive feature is the enlarged central cells of the forewing, you may need a hand lens to see it, but it does tend to give the grasshopper the appearance of having a broad wing.

Enlarged central cells on wing of Stripe-winged Grasshopper

By the end of the visit eight species of Orthoptera had been recorded, including the target species and 13 species of butterfly. Not bad for a blustery afternoon in Hampshire.

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