The Parasitic Fly Cistogaster globosa in Northants

Cistogaster globosa is a small but distinctive parasitic fly (Family Tachinidae) that is currently at its northern range limit in Northants. We have two records of it:
- a female at Bradlaugh Fields, Northampton in May 2011
- a male near Yardley Hastings in September 2015

Its main stronghold is the chalk of Berkshire and Wiltshire but it does pop up from time to time in other parts of south-east England. It is a parasitoid of the Bishop's Mitre Shieldbug Aelia acuminata. The two sites where it has been found in Northants are both flower-rich grasslands with fairly hot and dry soil conditions. It would be useful to see if this species occurs in similar habitats in other parts of Northants, particularly more northern sites as it might be expanding its range. Its current distribution can be found here:

https://data.nbn.org.uk/Taxa/NBNSYS0000030028/Grid_Map

Cistogaster globosa male. The female is is similar in shape and size but does not have the golden markings.

May 2015

A very belated summary for May. The weather was often cool or breezy and numbers seemed to be well down on previous years. However a few interesting flies were noted. 

We held two Hoverwatch sessions at Old Sulehay. The early May one did not turn up anything out of the ordinary but the late May session recorded Pipizella viduata and P. virens and, for the first time, Criorhina floccosa. After completing the formal counts we also recorded Criorhina berberina, Brachyopa insensilis and Brachypalpoides lentus. These last four species are all associated with dead wood or sap runs. The early May Hoverwatch did turn up the Conopid fly Myopa testacea. All Conopid records are much aprreciated as we only get a few each year. They are easy to recognise as a family but not quite so simple to identify to species as several look very similar.  

The moth traps at Pitsford turned up a few flies. The hoverfly Parasyrphus punctulatus, an early season species, was taken. This occurs in the moth traps most years but I get very few records of it from general fieldwork. Craneflies caught in the traps were Nephrotoma appendiculata and Tipula submarmorata.  

I have not received many records yet for May from other dipterists but amongst Kev Rowley's records was the hoverfly Paragus haemorrhous at Storton's Reserve. This is a new site for this species, which prefers short grasslands with bare patches that can heat up quickly in sunny conditions.

Northants and Peterborough Diptera Group April Meeting

The first field meeting of the year is always the last Sunday in April. Following the pattern of the past few years, a warm and very promising spell of weather had broken into decidedly cold and breezy conditions with the vegetation left wet after overnight rain. Not the most auspicious start to the season. We met at the roadside next to Mantle's Heath and walked over to High Wood and Meadow, Wildlife Trust reserve. The flush at the entrance to the reserve has recently had some maintenance work done on it and it looked very promising for later in the year. With the cold conditions, nothing was flying so it was a matter of sweeping the vegetation to see what turned up. The most productive area was the lower damp meadow where a mixture of rushes and grass tussocks provided some shelter for insects. The first craneflies of the season were just emerging and I found one male Tipula vittata close to the small stream at the bottom of the meadow. Several very small blackish craneflies turned out to be Ormosia lineata. These were identified from the male genitalia after dissection. Although the species is fairly widespread, it is not often recorded as it has an early flight season of April and May.

One member of the St Mark's fly family Bibionidae was caught - Bibio johannis.

Four species of hoverfly were found by me in the meadow: Melanostoma mellinum, Platycheirus clypeatus, Eupeodes latifasciatus and Eristalis pertinax. Hopefully other members of the group may have found some more. 

Damp meadows can be very good for dung flies, Scathophagidae, but I only found one species, a male Scathophaga inquinata.

With the meadow being rather unproductive I tried the wood as I thought the shelter might provide better conditions. The wood looks splendid at this time of the year with its carpets of bluebells and canopy of cherry blossom. However it did not yield much in the way of diptera. In fact I only took a single fly. This was the common Spring hairy-eyed cranefly, family Pediciidae, Tricyphona immaculata.

So, it was not a very productive start to the season but it was a very pleasant walk in a superb location.

April 2015

Since my last post I have received an earlier record of a hoverfly in Northants. On 2nd January 2015, Tim Newton found a hoverfly on his window which he correctly identified as Scaeva silenitica. We do not get many records of this species so it was a realyy remarkable find.

The warm weather in April has been bringing out the hoverflies, although I have not seen many species yet. There are loads of Eristalis pertinax about and there have been some Epistrophe eligans. The first record of this latter species came from Stuart Baker on 16th April at Southfield Farm Marsh. Graham Warnes found Melangyna quadrimaculata, another species with few records. Yesterday at Pitsford Reserve I found Helophilus hybridus and Melangyna cincta as well as a few very common species.

Earlier this week Bob Bullock sent me a photo of a blowfly he had seen at Pitsford in the Walgrave arm.  This is Cynomya mortuorum, a spectacular species with its metallic blue body and bright yellow face and jowls. We get few records of it although it is very distinctive. If you come across any recently dead animals it is worth looking round for this species. Bob said that there was a dead shrew nearby. Here is Bob's photo.

(C) Bob Bullock 2015

First Hoverfly?

I received the attached photo from Stuart Baker of the Wildlife Trust. He was working at the Southfield Farm Marsh reserve on 9th February and found this Marmalade Hoverfly Episyrphus balteatus sitting on his vehicle.

Episyrphus balteatus  by Stuart Baker

Now is the time of year in Northants when some hoverflies start to become active. Look in sheltered sunny places where the temperature will be a few degrees higher than the surrounding area. The usual first emergers are this species and the drone fly Eristalis tenax.

I attended the Dipterists Forum weekend wokshop at Preston Montford Field Centre over the weekend. This covered a general guide to identifying acalyptrate families and species identification to a group of these families where keys are not readily available. An update of Stuart Ball's key to Diptera families was provided. This included recent taxonomic changes and the workshop provided useful feedback to further improve the keys. The updated keys will be placed on the Dipterists Forum website in the members area.

Dipterists Forum workshop at Preston Montford - John Showers