What's in the box? No.13 - new to Nottinghamshire

The most recent coleopterous arrival by post came beautifully carded inside the lid of a screw-top plastic pot complete with a label detailing the location, collection date and name of the person recording it. It came from a reserve warden who had been in touch with me because they had identified the beetle as Longitarsus dorsalis, a species that did not appear to have been recorded before in the county in which they found it (Nottinghamshire) and wanted the identification confirmed (or otherwise).

The neatly set specimen of Longitarsus dorsalis as it arrived by post - carded inside the lid of a screw-top plastic pot.

Now onto identification. The beetle is about 2.5mm long (as ever, excluding appendages), with dark elytra bearing broad orangey side-stripes, a similarly orange pronotum and a dark head and appendages.

Dorsal view of L. dorsalis

Within the genus Longitarsus, this coloration is only known from L. dorsalis in Britain and the genus is easy to determine as the first tarsal segment is more than half the length of the tibia. So, it seems that the identification is straightforward to confirm, but it is worth looking more closely to see some other features associated with the species (some more details and further images can be found here).

Hind leg of L. dorsalis showing key features

In this photo, the long first tarsal segment is clear to see (red line) and the tibial spur (green line) is shorter than the maximum thickness of the tibia (sometimes this can be difficult to tell as the spur length may be very close to the max tibial width). The upper surface of the tibia is flat (too dark to tell here, but it is) and the outer edge of the tibia has a fringe of short flat bristles (red arrow).

Pronotum of L. dorsalis

The pronotum is orange, usually with at least a dark patch towards the front (clearly seen above). The pronotum also has a fine but distinct rim along the rear edge (also visible above) and sides. The pronotal punctures are fine and between them there is finer microsculpture. The elytral punctures are coarser than those on the pronotum and the elytra themselves have definite 'shoulders'.

Head of L. dorsalis

The head is also densely microsculptured and although this isn't visible in the photo above, you can see the coarse punctures along the edge of the eye.

Side view of L. dorsalis showing the epipleura narrowing towards the rear (red lines).

In side view, the epipleura (lower edges of the elytra) narrow towards the rear, especially behind the mid-point (approximately where the left-hand red 'I' is in the photo above). Lastly, I want to look at the aedeagus (below) which is often a useful diagnostic tool when identifying some trickier-to-separate beetles. Here, the tip unfortunately broke off during dissection (though it did have a small blunt point), but the sides clearly curve inwards and the shape matches the better specimen illustrated here. The parameres (lateral lobes) can be seen as the dark V-shaped structure near the bottom. Interestingly, the curved sides of the aedeagus, an important feature, are not clearly shown in the usually excellent (and expensive) work by Warchałowski (2003).

Aedeagus of L. dorsalis

This clearly indicates that the specimen is of L. dorsalis which is important as it is the first time it has been found in Nottinghamshire, and is nationally scarce in the UK (Notable B). It is mainly found on calcareous or sandy soils, is associated with ragworts (Senecio), and has become scarce due to the loss of its habitats (conversion of grassland to agriculture, infilling of quarries, habitat succession such as in once-open woodland rides and clearings, grassland 'improvement' through fertiliser application, herbicide use and woodland clearance). Open conditions with ragwort are required and conservation measures can be straightforward e.g. retaining some open areas in woodland through rotational cutting, or grazing is some other situations (Hyman, 1992). So, it's good to see this species in a previously unrecorded location, especially as several individuals were seen with just one sent to me for identification.

References

Hyman, P.S. (1992). A Review of the Scarce and Threatened Coleoptera of Great Britain. Part 1. JNCC, Peterborough.

Warchałowski, A. (2003). The Leaf-beetles (Chrysomelidae) of Europe and the Mediterranean Area. Natura Optima Dux Foundation, Warsaw.