Synosis Townes

Broad, Gavin R. & Shaw, Mark R., 2005, The species of four genera of Metopiinae (Hymenoptera: Ichneumonidae) in Britain, with new host records and descriptions of four new species, Journal of Natural History 39 (26), pp. 2389-2407 : 2398-2399

Genus Synosis Townes

Identification of Synosis species

Species of Synosis have primarily been differentiated on the basis of differences in propodeal carina patterns (e.g. Kusigemati 1968; Tolkanitz 1984). However, Synosis is a rarely collected genus, ranging across the Holarctic and into the Neotropics, and the trickle of new species described ( Townes HK and Townes M 1959; Kusigemati 1968, 1971; Vikberg 1972; Tolkanitz 1977, 1984, 1986; Gauld and Sithole 2002) suggests that there may be quite a few more species yet to be discovered, or, alternatively, that some species are more variable than has yet been appreciated. The specimens in NMS, collected from across the UK, show quite considerable variation in the propodeal carinae, and this has made species delimitation difficult, some of this variation being sex-related. For the two most similar species treated here ( S. caesiellae and S. parenthesellae ), the number of flagellar segments seems to be a constant specific difference, albeit from only small sample sizes. The most recently collected specimens are 9 years old and an attempt to obtain a 28S D2 rDNA sequence from a leg failed. It is to be hoped that molecular sequences may help clarify species boundaries for specimens preserved in alcohol in the future. We have separated our Synosis specimens into three species but the limits of these species would need to be reassessed if substantial additional material were to be obtained.

We have examined specimens of S. clepsydra Townes at the BMNH, the holotype of S. meridionalis Tolkanitz , a paratype of S. orientalis Tolkanitz , and the holotype and a paratype of S. karvoneni Vikberg , which includes all of the described species most likely to be present in Britain (and S. orientalis , a very unlikely candidate species, described from the Kuril Islands, in the Russian far east; Tolkanitz 1984). Not one of these species appears to be represented in the British material which we have examined. Synosis karvoneni is a smaller species than any of those treated here and is best separated by the larger, angulate lobe at the anterior end of the submetapleural carina (smaller and rounded in the other species) and the presence of a vestigial fore wing vein 3 rs-m. Synosis clepsydra differs distinctly in colour pattern, having more extensive yellow on the face that fills the malar space and extends further back towards the occipital carina than in any of the other species examined. Yellow also extends up the frons (i.e. above the antennal sockets) on the inner orbit, which is uniformly dark in other species examined. In addition, S. clepsydra has the metasomal tergites with reddish borders. Synosis meridionalis has a brighter yellow face (rather dull yellow in all of the British species) with the malar space completely yellow and sharply demarked from the dark brown of the gena (demarcation ill-defined in British species). The lateromedian longitudinal carinae of the propodeum converge anteriorly to a narrow carina, unlike the British species in which the area of convergence is always as broad as or broader than the thickness of the carinae combined (compare Figures 21 and 22 with Tolkanitz 1977, Figure 4 , and Gauld and Sithole 2002, Figure 48). Synosis orientalis is relatively distinctive owing to the black flagellum (yellow/brown ventrally in the other species examined), and the raised lateral sections of the posterior transverse carina of the propodeum to form incipient apophyses.

As the species of Synosis are so similar we present a generic diagnosis followed by short species accounts emphasizing those features of value in specific identification. Because the ovipositor of females is short and easy to overlook when it is sheathed it is easy to mis-attribute the sex of individuals. Females have a longer last metasomal sternite than males, as illustrated by Gauld and Sithole (2002, p 12). In some species there are distinct sexual differences in the extent of yellow on the face and the number of flagellar segments.

Generic diagnosis for British species

Face and clypeus forming a rather uniformly convex surface, no groove separating the clypeus from the face ( Figure 12 ); frons lacking an inter-antennal lamella and face lacking a transverse ridge before the antennae ( Figure 12 ); mandible narrow with lower tooth shorter than upper tooth; notauli distinct to about half the length of the mesoscutum, mesoscutum punctate; metasoma shallowly punctate, punctures especially obvious on first tergite; first metasomal tergite with a pair of median carinae ending at about two-thirds of the length; body rather evenly covered in setae; propodeum with distinctive pattern of anteriorly converging lateromedian longitudinal carinae; anterior transverse carinae present or absent, sometimes replaced by grooves; posterior transverse carina complete and strong; mid tibia with anterior (outer) spur shorter than posterior spur (the opposite to most metopiine genera); ovipositor short, not projecting beyond apex of metasoma; aedeagus dorsoventrally flattened; colour: mesosoma and metasoma dark brown, legs and tegulae reddish except for hind coxae which vary from pale reddish to dark brown with red apically, face dull yellow, underside of scape, pedicel and flagellum dull yellow, flagellum becoming brown apically, upperside of antenna dark brown.

Figures

Figure 12. Synosis caesiellae ♀, head, anterior view.

Figures 19–22. Synosis caesiellae. (19) ♀, Port Appin, dorsal view of head showing ocelli. (20) ♀, Port Appin, propodeum. (21) ♀, Berrie Dale, ex?Carpatolechia, propodeum. (22) „, Burghfield, ex Swammerdamia, propodeum.

Figures 2–5. Apolophus borealis ♀. (2) Head, lateral view, showing narrow mandible. (3) Head and fore leg, showing long malar space and foreshortened tarsal segments. (4) Metasomal apex, showing large hypopygium. (5) Whole insect, lateral view.