'Tis Psallus Time, Tra-la-la-la-la

Excuse the Fakespeare subject line, but if you fancy a challenge, it's time to get out there beating the trees for Psallus spp. 

Colourful and common, many of the species in the Family Miridae are often a tricky to identify. The genus Psallus possibly is possibly the most challenging group. We are about to be swamped by the annual deluge of Psallus species, but these oh so common and under-recorded bugs can be identified with a bit of effort. There are 23 species on the UK Checklist:

Psallus albicinctus, Psallus anaemicus, Psallus ambiguus, Psallus assimilis, Psallus betuleti, Psallus confusus, Psallus falleni, Psallus flavellus, Psallus haematodes, Psallus helenae, Psallus lepidus, Psallus lucanicus, Psallus luridus, Psallus mollis, Psallus montanus, Psallus pardalis, Psallus perrisi, Psallus pseudoplatani, Psallus quercus, Psallus salicis, Psallus variabilis, Psallus varians, Psallus wagneri.

The Leicestershire and Rutland (VC55) list currently stands at nine species. Some of these can be tentatively identified from (detailed) habitus photos (see notes below). However, the truth is that most require dissection of the male aedeagus for confident identification. So how to tackle these common bugs? Here are my tips:

• General guide to the genus Psallus: Arboreal Mirid species, length = 3-5mm. (Suggestion - if you can't confidently identify bugs as members of the Miridae, save yourself the pain and start by practicing on easier genera). Antennae long; second antennal segment slender, in males wider, as long as or slightly longer than posterior width of pronotum; third antennal segment two thirds the length of second segment; head of male smaller than that of female; eyes of male, in profile, covering head entirely; rostrum reaching the middle of venter, first segment reaching the middle of the xyphus; tarsal segments slender; third segment of the hind tarsus shorter or scarcely longer than the second segment and noticeably shorter than the first and second segments combined. If ant1 black then length >4mm. With a little practice you get pretty good at recognizing the genus on sight. 
• Beating tree foliage from late spring-autumn is the way to find Psallus. The host species is often helpful, so note this. Psallus picked up from random sweeping etc are harder to get to grips with. 
• Top Tip: Find a male and dissect the aedeagus! With a couple of exceptions that can be done from habitus, dissection is required. In theory females can be identified, but with a couple of exceptions I don't bother - it's too hard! I am happy to receive male specimens from VC55 for confirmation if you don't fancy doing this yourself. 

Resources: 

Bernard Nau's draft 2012 key to the Miridae is very good and has useful (if tiny) drawings.

Denise Wyniger's Doctoral dissertation from the University of Basel is the best resource available, but it does cover all European species and is a bit overwhelming at first. The aedeagus drawings are particularly useful: Wyniger, D. (2004) Taxonomy and phylogeny of the Central European bug genus Psallus (Hemiptera, Miridae) and faunistics of the terrestrial Heteroptera of Basel and surroundings (Hemiptera). Available at: https://edoc.unibas.ch/79/

VC55 species and notes:

Psallus ambiguus - Length >4.4mm. Ant1 black, ant3 straw, A2 black with basal half straw in ♀, ♂ dark red-brown to black, ♀ red to reddish-black. On a range of deciduous trees.

Psallus betuleti - Length 5.1mm. Upperside black; cuneus dusky with base broadly pale, outer margin narrowly reddish. Apical process of aedeagus elongate, slender, underside almost straight. On Birch. 

Psallus falleni - Length 4mm. Brownish-red, cuneus broadly white at base (white>hind tibia thickness) & very narrowly white at apex. July-September, mainly on Birch. 

Psallus flavellus - Length 3.8mm. Orange-red.

Psallus lepidus - Length 4.1mm. ♂ dark red-brown to black, ♀ red-brown to orange-brown.

Psallus luridus - Length 4mm. Upperside & antennae drab, yellowish-grey or grey-brown, dark spot on corium towards apex; dual pubescence, dark & pale. Brown points on pronotum and inner face of ant1. Femora with black spots, apex reddish. Tibia with dark spines in black spots. Head large, with long gula (throat). On Larch. 

Psallus perrisi - Upper black to black-brown, at most a slight reddish tinge, ♂  blacker than ♀; femora blackish. c.f. P. wagneri, aedeagus required. 

Psallus varians - Length 4.1mm.  Claws evenly curved; on Oak. 

Psallus wagneri - Upper dark red to dark yellowish-brown, femora dark red. c.f. P. perrisi, aedeagus required. 

 Good hunting! 

 

Update: Psallus perrisi vs Psallus wagneri

Arto Muinonen commented on the British Terrestrial Bugs Facebook group.  Muinonen's aedeagus drawings are similar to that of Wyniger, D. (2004).  Both of these are quite different to Nau's drawings, so I've reached that conclusion that all but one of the Leicestershire specimens to date are in fact Psallus perrisi. Muinonen also commented that P. perrisi is more frequent than P. wagneri in Finland, and my findings seem to confirm this. Now it gets complicated!  Muinonen has unpublished DNA work which agrees with Wyniger that perrisi and wagneri are synonyms and that differences in the aedeagus are intraspecific variation.   Oh dear!