Kleidocerys privignus

Kleidocerys resedae, the Birch Catkin Bug, is a familiar and very common species of Lygaeid. Two closely related species are more problematic. Kleidocerys ericae was differentiated from K. resedae based on pigmentation and the fact that it feeds on heathers (Erica spp but not Calluna so I'm told). Kleidocerys privignus also has a different pigmentation pattern and feeds on Alder (Alnus). My natural inclination is to be a taxonomic lumper so I'm inclined to disregard the pigmentation differences (intermediate forms occur) and the food plant preferences (which laboratory rearing experiments have shown are not absolute) and regard all three as a single species. My ultimate authority on Hemiptera, Pericart, wasn't sure about these three, and without the benefit of DNA analysis hedged his bets, so no clear answer there. I was able to live with that until recently when I did some DNA analysis which implies that all three are indeed distinct species, see: https://ajcarthropoda.blogspot.com/2025/02/the-kleidocerys-conundrum-resolved.html

Which brings us to the question at the heart of this - what is a species? These days, the answer depends a lot on who you ask, but everyone agrees that it's now a lot more complicated now than when the species concept was developed. I'm afraid I have the old-fashioned opinion (which is bound to upset some) that a species is a group of organisms which are reproductively isolated. There are lots of ways to be reproductively isolated, e.g. pioneers trapped on an island, but it is also possible to be reproductively isolated behaviourally. A good example of this is the wolf spider Pardosa lugubris. This was split into two species based on observations of the male courtship dance (Cryptic species and behavioural isolation in the Pardosa lugubris group (Araneae, Lycosidae), with description of two new species. (2000) Bulletin British Arachnological Society, 11(7), 257-274). Being eaten by the female if she rejects your dance moves is pretty strong selection leading to reproductive isolation. Which brings us to Kleidocerys again. Like many Hemiptera, Kleidocerys communicate by stridulation. In this genus, sound production may not to be associated with mating but occurs when they are disturbed, perhaps as a territorial statement. K. ericae stridulates at a frequency of 16 Hz while K. resedae uses a lower frequency of 8 Hz (Stridulation and its analysis in certain Geocorisae (Hemiptera Heteroptera). (1957) Proceedings of the Zoological Society of London, 129 (3): 351-358). This is equivalent to the Pardosa mating dance and is likely to cause reproductive isolation, which is borne out by the DNA analysis of the two species. I don't know about stridulation frequency in K. privignus but the DNA analysis means that if we accept K. ericae as a distinct species from K. resedae, we have to do the same for K. privignus. 

Recently I sampled 20 Kleidocerys specimens from Alder here in Leicestershire. My overall impression is that they are quite variable in pigmentation, but in my sample, 1 out of 20 specimens has the pigmentation described for Kleidocerys privignus, the others appearing to be variants of the extremely common Kleidocerys resedae. 

The upshot of all of this is that while it's not clear if K. ericae occurs in VC55 (we have limited heather here), I think it's clear that K. privignus does. Now we need boots on the ground to get out there and figure out the field ecology. 

Many thanks to Jim Flanagan for helpful discussions, and for sharing this interesting paper: 

Davranoglou, L.R., Taylor, G.K., & Mortimer, B. (2023) Sexual selection and predation drive the repeated evolution of stridulation in Heteroptera and other arthropods. Biological Reviews, 98(3), 942-981.