A revision of the robberflies (Asilidae) of the Sefton Coast sand-dunes

Introduction

Smith & Kinsella (2020) reported on six robberflies (Asilidae) they had recorded and photographed in the Sefton Coast sand-dune system, suggesting that four more species might be discovered through field survey, namely Dioctria atricapilla, D. rufipes, Leptogaster cylindrica and Pamponerus germanicus. During the spring and summer of 2020 and despite Covid-19 restrictions, field work resulted in three of those taxa being photographed in the dunes. In addition, several more sightings were made of D. baumhaueri and Lasiopogon cinctus, for which there were few previous records.

Species accounts

Dioctria atricapilla Violet Black-legged Robberfly

There had been two earlier Sefton Coast records but our first was on 8^th June 2020, when PHS photographed two males and a female a few centimetres apart in long grass in a sheltered woodland glade at Hightown sand-dunes (tetrad SD20W) (Figs. 1&2). PK found two males on 9^th (Fig. 3) and a singleton on 14^th June in the same place. This is a widespread but local species in England extending as far north as Yorkshire.

Figure 1. Dioctria atricapilla male

Figure 2. Dioctria atricapilla female (PHS)

Figure 3. Dioctria atricapilla male, Hightown dunes (PK)

Dioctria baumhaueri Stripe-legged Robberfly

The Sefton Coast is near to the northern limit of this robberfly, which is fairly widespread in England and Wales. There had been only two records here before PHS found one at Range Lane, Formby, on 1^st July 2019 (Smith & Kinsella, 2020). In 2020, PHS photographed singles at Range Lane (Fig. 4) and nearby Ravenmeols dunes on 2^nd June 2020 (both SD20X) and again at Range Lane on 20^th June. PK had one at Alexandra Park, Crosby (SJ39E) on 12^th June (Fig. 5) and two at Blundellsands Key Park (SJ39E) on 17^th June, finishing off with one at Hightown on 25^th June (SD20W).

Figure 4. Dioctria baumhaueri with prey, Range Lane, Formby (PHS)

Figure 5. Dioctria baumhaueri, Crosby (PK)

Dioctria rufipes Common Red-legged Robberfly

While recording in the Hightown glade on 1^st June 2020, PK photographed a specimen of Dysmachus trigonus with prey (Fig. 6) (SD20W). Based on leg and antennal characters, the prey species appeared to be Dioctria rufipes, this being confirmed by Diptera expert, Phil Brighton. It was the first record of D. rufipes in Sefton but was followed the next day by two more sightings of single individuals, by PHS at Range Lane, Formby (SD20X) (Fig. 7), and PK again at Hightown. The Formby specimen had prey that was identified by Tony Hunter of World Museum, Liverpool, as the ichneumon wasp Diplazon laetatorius. This parasitic wasp is thought to be fairly common but there are few confirmed records nationally. PK counted five specimens of D. rufipes in the Hightown glade on 9^th June 2020 (Fig. 8) and one at Crosby Coastal Park (SJ39E) on 13^th June. This distinctive Robberfly is widespread in much of England and Wales, extending north to eastern Scotland.

Figure 6. Dysmachus trigonus with Dioctria rufipes prey, Hightown dunes (PK)

**Figure 8.** *Dioctria rufipes* with unidentified prey, Hightown dunes (PK)

Leptogaster cylindrica Slender-striped Robberfly

PK photographed the first for the Sefton Coast at Ainsdale NNR (SD20V) on 24^th June 2020 (Fig. 9). We had no more sightings in 2020. This species was expected to appear here as it is has been spreading north in recent years. The first Lancashire record was in 1961, since then it has become one of the commonest asilids in the region (Brighton, 2017).

Figure 9. Leptogaster cylindrica, Ainsdale NNR (PK)

Lasiopogon cinctus Spring Heath Robberfly

Smith & Kinsella (2020) reported that L. cinctus had been recorded several times on the Sefton Coast, the most recent having been photographed by PHS on 14^th May 2019. April/May 2020 proved to be productive for this nationally scarce robberfly. Between 10^th April and 3^rd May, PHS had seven records of nine individuals, including two pairs, at two sites: Wick’s Path, Formby Point (SD20T), and Ravenmeols woods (SD20X). At the former locality, the insects were basking on a south-facing fence (Figs. 10&11), while at Ravenmeols they were on a sunny, sheltered woodland edge dominated by Sycamore (Acer pseudoplatanus) (Fig. 12).