Hyposoter caedator ( Gravenhorst, 1829 )

Galsworthy, Anthony, Shaw, Mark R. & Haraldseide, Håkon, 2023, A key to European species of Hyposoter Förster, 1869 (Ichneumonidae: Campopleginae) with descriptions of 18 new species, and notes on all included species, Zootaxa 5290 (1), pp. 1-73 : 36

Hyposoter caedator ( Gravenhorst, 1829)

Campoplex caedator Gravenhorst, 1829 : lectotype ♀ in UWCP, designated by Horstmann (2000), examined by Horstmann.

syn. Anilastus persimilis Szépligeti, 1916 : lectotype ♀ in HNHM, designated by Aubert (1965), examined by Horstmann (synonymized in Aubert, 1965)

syn. Anilastus parvulus Kiss, 1926 : holotype ♀, in HNHM, designated by Aubert (1965), examined by Horstmann (synonymized in Aubert, 1965)

Horstmann observed in a note attached to his draft key that this was an extremely difficult species to pin down, and this is indeed so. Horstmann (2000) records that the lectotype has the head, large parts of the thorax, all legs and 1 fore and 1 hind wing missing, but that what remains agrees with the types of Anilastus persimilis Szépligeti , and A. parvulus Kiss , which he had also examined. There is a long series identified as caedator in Horstmann’s material from Moraira near Alicante in Spain, which includes several colour forms which Horstmann had marked as ‘dark form’, ‘half dark form’, and ‘pale form’. The darkest of the dark forms seems to be similar to the form named by Aubert as subspecies corsicator. The fact that all these forms occur in the series from Moraira suggests that these are colour forms of the same species, but it is possible that they conceal a species complex: molecular investigation might help to clarify the situation.

The best distinction from most similar species is the narrow, rather convex clypeus and the slightly inward sloping eyes when seen from the front, which give the head a triangular appearance. The lower mesopleuron is granulate, with no or only very small punctures visible. Hyposoter dubitatus shares both these characteristics, but has a broader and shorter area superomedia, and the speculum is fully granulate, whereas in caedator the granulation on the speculum normally becomes so fine that it creates a shining area distinct from the rest of the mesopleuron. The area superomedia in caedator is long and narrow, and not separated from the area petiolaris.

The fore and mid coxae of caedator vary from yellow in the pale forms to black in the dark forms, with intermediate states ranging from orange to brown frequently occurring. The hind coxa is always black. The hind tibia is usually pale orange with rather vague darkening at base and apex. The first tergite and the anterior part of the second tergite are always black. The rest of the metasoma may be entirely orange, orange with the terminal segments dark brown or black, mainly black with lateral orange markings on the second and third tergites or entirely black. Consequently this species appears at a number of different points in the key.

We have seen specimens from Germany, the Netherlands, the UK, France, and Spain: it has been recorded in the literature from most of Europe, but it is impossible to know whether the references are to Horstmann’s concept of caedator .

A specimen in NMS was reared in the Netherlands by R. Majoor from the sterrhine geometrid Idaea seriata (Schrank) . A further specimen in NMS was reared in Edinburgh from an unknown geometrid feeding on ivy-leaved toadflax, Cymbalaria muralis . There are older records listed in Yu et al (2016) from two other geometrid moths and a sawfly: because of difficulties of identification, these cannot be relied upon, and the record from a sawfly will certainly be erroneous.

We have also seen a further species which appears to be common in the UK, and which is very similar to both the present species and to H. dubitatus in size and general coloration, but which can be separated from both by its broader and flatter clypeus, larger mandibles, longer temples, and the presence of clear punctation on the lower half of the mesopleuron on a granulate background. The area superomedia is long and narrow, as in caedator . We believe that this species is probably an Olesicampe , but cannot be sure in the absence of rearing records.