Ophion longigena

I spent over two hours attempting to key this using both Gavin Broad's key to nocturnal Ichneumonidae and the Swedish review by Johansson and Cederberg, before arriving tentatively at longigena. I had a number of concerns with this ID, not least that the lateral carinae of the scutellum are strong in the basal half which is contradicted in GB's key. I returned to it after a few weeks and spent another 2 hours carefully working through both keys. I remained stumped using GB's but eventually arrived at longigena again with some degree of confidence using the Swedish review. Reading the account of longigena in that review I spotted something I'd missed first time around, which is that yes, the scutellum should have distinct lateral carinae at least in basal half. It looks like longigena often has weaker propodeal carinae than my specimen, but I can't see anything that goes against identifying it as longigena. Of course I always welcome feedback, but unless anyone disagrees I think I'm happy to call this longigena.

My passage through the key in the Swedish paper runs as follows:

• Couplet 1: occipital carina complete, wing membrane not strongly yellow - to couplet 3.
• Couplet 3: head and body lack conspicuous black marks except darkened tip of abdomen; wing membrane not strongly yellow - to couplet 4.
• Couplet 4: forwing >14mm; propodeeal carinae strong; radius not strongly thickened at junction of pterostigma - to couplet 5.
• Couplet 5: propodeal carinae are almost complete but not shaped as shown in Fig. 10O (forticornis). With 55 flagellomeres I think it's safe to rule out forticornis (which sounds pretty unlikely anyway). Propodeal carinae are pretty strongly raised but I think we have to go on to couplet 6 here.
• Couplet 6: At the ventral midline the sclerotised part of sternite 1 ends directly below the spiracle. Lateral carinae of scutellum are strongly indicated anteriorly, to about half way, but this seems to be permitted "rarely". Ramellus present so first exception in second half of couplet is ruled out. The other excpetion (longigena) has a "strongly buccate head" - mine is buccate, so I think I should see if couplet 28 leads to longigena. But first I will go on to couplet 7 and see if that leads anywhere satisfactory.
• Couplet 7: 55 flagellomeres - to couplet 8.
• Couplet 8: First flagellomeres are a little over 3.5x longer than wide which fits the first option better than the second, though the inclusion of the word "usually" in the second option means this is not wrong. Pleurosternal angle right-angled and hardly rounded, and only slightly anterior to the sternal angles (closest to B in Fig 9), so this suggests second option is the correct one to take. However the ovipositor sheath does not appear to be contrastingly dark, so I am not sure which way to go here. I will try both options (couplets 9 and 22).
• Taking the first option first, couplet 9: first option is ruled out by the radius being clearly sinuous and there being a big gap between the lateral ocellus and the eye; however, for the second option the posterior transverse carina of propodeum is not widely interrupted, or interrupted at all. This character is caveated with "usually" and the other elements for the second option are ok, so to couplet 13.
• Couplet 13: I found it difficult to view the hind trochanter correctly but judge it to be closest to F in Fig 7; mandibular gape right-angled (or a little more than) with clear internal angles. Pale markings on mesosoma are not particularly conspicuous but in view of other characters it has to be on to couplet 15.
• Couplet 15: Mesosoma lacks pale markings as in Fig 11 A&B - to couplet 17.
• Couplet 17: Temples are not quite as strongly buccate as Fig 18B, mesosoma is not brownish and if subarcticus in Sweden is very rare in subalpine mountains I think it's probably safe to assume it won't be in lowland Norfolk. However, the distance between eye and lateral ocellus is well over 0.4x the width of that ocellus, so I think we are at a dead end.
• So taking the second option from couplete 8, couplet 22: Temple is buccate, roughly as long as the eye and there's a clear gap between eye and ocellus - to couplet 23.
• Couplet 23: Prosternal angle not as acute as shown in Fig 9F, though perhaps marginal; hard to judge relative prominence of facial punctures but not contrastingly densely punctate below the antennal sockets; only 55 antennomeres - to couplet 24.
• Couplet 24: The distance between the upper end of the tentorial pits and compound eye is over 0.6 times the distance between the pits. I think that rules out borealis, though it's questionable whether it's close enough for crassicornis or not (should be 0.5 itmes the distance). I'm doubtful that the facial punctures are deep enough for crassicornis, but difficult to say without much comparative material. The anterior transverse carina of propodeum is not strongly curved as in Fig 14D - it is longer and straighter. I have caught crassicornis before and this does not appear to be the same species with, for example, the third antennomere being clearly longer. I think we have another dead end here, so will now investigate longigena as considered at couplet 6.
• Returning to the exception from couplet 6, I will now see if couplet 28 leads to that exception (longigena). Couplet 28: Sclerotised section of sternite 1 is not (at least ventrally) posterior to the spiracle, so to couplet 29.
• Couplet 29: mesosoma entirely testaceous and no dorsal undulation on tergite 1 - to couplet 31.
• Couplet 31: hind femur not as slender as in Fig 16C and not early spring, but longest hind tibial spurs not as long as 0.5 x first tarsal segment. Arguably therefore another dead end, but it does say "about" 0.5 times, so I'm going to go with 0.42 times being close enough, so to couplet 33.
• Couplet 33: subapical flagellomeres are about twice as long as wide (or a little less) and central flagellomers about 1.4 times as long as wide; temple buccate with distinct gap between eye and ocellus - to couplet 34.
• Couplet 34: temples buccate, as wide as eye in lateral view. I find judging face width difficult and subjective but I can't see much differnce compared to Fig 20C; posteria segments of metasoma are dark. I'm not sure I've looked at enough Ophion mandibles to judge whether these are worn, but maybe a bit - certainly the teeth edges are bit uneven in places. If I've arrived here correctly then longigena it must be.

The forwing was somewhere between 14mm and 15mm.

apparent Ophion longigena showing mandibles, close-up of face showing distances between tentorial pits & eye, antennae with close-ups of first flagellomeres (two views), subapical flagellomeres and central flagellomeres, lateral ocellus and eye gap, temples from above and side, epicnemial carina, scutellum (2 views), propodeum (2 views), first metasoma segment, tip of abdomen, hind femora, hind tibial spine and first tarsal segements and wings, Wendling Beck Environment Project (Norfolk, UK), 6th July 2023