Review of the Palaearctic (and Oriental) Allurus (Braconidae, Euphorinae) based on material from Sweden

Abstract Background The tribe Centistini includes three genera, Allurus, Centistes and Centistoides (Stigenberg et al. 2015). They are solitary endoparasitoids of adults and final instar larvae of beetles from the family Curculionidae (Jackson 1920, Aeschlimann 1980, Tobias 1986) New information In this paper we present a key, molecular data (standard DNA barcode, CO1) and images of the two species of Allurus occurring in the Western Palaearctic. A third Oriental species described from China (Taiwan) is also included in the key. Allurus is a Holarctic genus with three known species (A. choui, A. lituratus, A. muricatus). Our sequence data confirms that A. muricatus and A. lituratus are two distinct and separate species and this paper points out good and easy characters to separate them.


Introduction
The genus Allurus Förster contains fairly large euphorine wasps of 3-4 mm body length. It is a Holarctic genus with extralimital species in Taiwan. In this paper we present a review of the species of Allurus based on morphological study of the types and morphological and molecular study of the material available at NHRS. The Allurus are rare, but as they parasitize on the very common coleopteran genus Sitona (Curculionidae), they probably are more common than we think. Brammanis (1932) writes that this parasite grabs its prey with a sudden jump, mounts the beetle transversely at the front and pierce the ovipositor in between the pro-and mesothorax Fig. 1. For the beetle it is impossible to escape from this situation. The pupation takes place in a cocoon on the ground. The cocoon is 3 mm in length, pale cream colour, covered with some loose flocculence and constructed among moss on ground (Jackson 1920.) The pupal stage lasts for 12-13 days. Illustration in Brammanis 1932 of a A. lituratus attacking its prey, a Sitona beetle.

Materials and methods
All specimens in the collections at the Swedish Museum of Natural History were collected with Malaise Traps. Five specimens of A. lituratus were collected within the Swedish Malaise Trap Project (SMTP). Two specimens were collected by A. Ohlsson in 2011. The single specimen of A. muricatus was collected in a allotment garden by T. Malm and M. Malm in 2012. Terminology used for morphological and wing structures follow Wharton et al. (1997)and Goulet and Hubert (1993)

Diagnosis
The genus Allurus is diagnosed by having bifurcate claws, hind coxa with more or less developed ventral denticle, first metasomal tergite sessile, broad and strongly curved ovipositor, first subdiscal cell (2Cu) open, vein 2-1A (A) on fore wing not reaching wing vein 2Cua (Cu), laterope usually hardly visible.

Distribution
Eastern Palaearctic and Western Palaearctic.
Lateral habitus of A. muricatus. Image of voucher specimen JS10_00405. The scale bar equals 1 mm.

Analysis
The analysis of the sequences revealed a nucleotide difference of 12.5% (82 bases differing) between the sequence of A. muricatus and the four sequences of A. lituratus. The intraspecific variation among A. lituratus was within 1.5% difference, with the specimen JS10_00409 differing from the other A. lituratus with 7-9 bases. There was no specific part of the sequences where the nucleotid disagreements between the two species were aggregated, they were spread all over the 658 nucleotide bases (Fig. 11).  Alignment showing the disagreements between sequences of the Allurus specimens.

Discussion
The SMTP has collected insects since 2003 through out Sweden and that the result of those trappings should be only a handful of Allurus specimens is rather strange, that is, in relation to the common occurrence of the host genus. The Sitona are rather common all over Sweden and found even in Jukkasjärvi, 200 km north of the Arctic circle (SLU, Swedish University of Agriculture 2015). The Swedish Allurus speciemens were only collected in the following southern provinces: Skåne, Småland and Sörmland. Hopefully this paper will increase the interest and effort for amateurs to collect and identify braconid wasps.