Thursday, 3 October 2024

Lygus Identification for Dummies (like me)

For some time I have been unhappy about my ability to determine the species of certain Lygus specimens. A typical Lygus pratensis is easy - based on "shinyness" (pubescence) of the elytra and markings on the scutellum. (Having said which, the extent of seasonal colour variation in L. pratensis has only just dawned on me - not quite as extreme as Palomena prasina but not far off.) Likewise, a typical Lygus rugulipennis is easy - dull (pubescent) appearance. However, not all specimens are typical. A short time ago I found an atypical Lygus - quite shiny with Lygus wagneri-like markings on the scutellum: 
"Lygus mysteriosus"

Such specimens are a problem. I find Nau's illustrations of the pubescence of the corium unhelpful (and he acknowledges the difficulty in distinguishing between certain specimens of L. pratensis and L. wagneri - Nau, B. (2004) Identification of plantbugs of the genus Lygus in Britain. Het News Issue 3, p11). 

Namyatova et al (2022) published a study of Lygus species including both habitus characters and male reproductive anatomy (Namyatova, A.A. Tyts, V.D. & Bolshakova, D.S. (2022) Identification and delimitation of the trans-Palearctic Lygus species (Insecta: Heteroptera: Miridae) using integrative approach. Insect Systematics & Evolution, 54(2), 146-192). According to Namyatova et al the overlap between L. pratensis and L. wagneri is explained by the fact that they are synonymous based on DNA homology, something which fits with observations of habitus. Leaving taxonomy issues to one side, the drawings of the spicule and the presence or absence of teeth on the right side of the small lobe of the vesica make distinguishing Lygus species (backed up by habitus) relatively straightforward. Although only males can be determined and dissection is required, this is at least a definite way of identifying atypical specimens with certainty. 
Lygus vesica

The issue now is that I have yet to encounter L. wagneri! Although we do have one record of this species in VC55 I am not convinced that it occurs here. However I am confident that if I do ever find a male L. wagneri I will be able to identify it with certainty! 
 
 
 

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