Psallus ? varians

Identification & Distribution

Psallus species are small mottled red, grey or dark brown bugs with the pronotum and forewings covered in scale-like golden hairs and with the tibial spines arising from black spots. Adults of Psallus varians are difficult to separate from other Psallus species. Judging by the photos available of this species, they are often golden brown with an orange-red suffusion on the cuneus (see first picture below).

Psallus varians is one of the most common Psallus species on beech (Fagus), although it is usually considered to be an oak (Quercus) specialist. It is also found on willows (Salix), birches (Betula), whitebeams (Sorbus), hazels (Corylus), alders (Alnus) , and ash (Fraxinus). They feed both on tree pollen and aphids. There have been more cases of man-biting with Psallus varians than with many others. In Germany in the summer of 2016 there was a swarming phenomenon and many people were bitten. The 'sting' can be painful, and puncture wounds were said to be inflamed.

Biology & Ecology

Floren & Gogala, 2002 used insecticidal knockdown fogging to obtain a quantitative sample of arthropods living in the forest canopy. Psallus varians was found in all samples from beech, and was one of the dominant Heteroptera on that tree, along with Psallus ambiguus.

We have found Psallus varians inside the folded leaf galls formed by the aphid Phyllaphis fagi on beech and observed the bug predating this species of aphid. The aphid is heavily coated with wax, but this does not dissuade this predator from feeding on the aphid. Our impression is that wax provides much less of a defence against sucking predators (such as Psallus) than against chewing predators (such as coccinellids).

We have also experienced man-biting by this species. Although they are not supposed to imbibe blood when they bite, the photo below might suggest otherwise!

Acknowledgements For the mirid bugs we have used Southwood & Leston (1959) and British Bugs to aid in identification and for the key characteristics. For aphids we have made provisional identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994) and Blackman & Eastop (2006) supplemented with Blackman (1974), Stroyan (1977), Stroyan (1984), Blackman & Eastop (1984), Heie (1980-1995), Dixon & Thieme (2007) and Blackman (2010). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks

References  Floren, A. & Gogala, A. (2002). Heteroptera from beech (Fagus sylvatica and Silver Fir (Abies alba) trees of the primary forest reserve Rajhenavski Rog, Slovenia. Acta Entomologica Slovenica 10(1), 25-33. Abstract