Species of the Month May 2024

Trioza centranthi

During 2024, our 20th anniversary year, we are revisiting our Species of the Month archive to reshare some of our "greatest hits" through the years. This month we are going back to January 2020, and the very under-recorded True Bug Trioza centranthi. The number of records has over quadrupled from 18 to 82 since we first made it Species of the Month, but there is sure to be many more galls going unnoticed. Can you help bump the numbers further?

Trioza centranthi is a species of True Bug (Homoptera) which are difficult to identify as adults. Fortunately the nymphs form distinctive galls on the leaves of Red Valerian (Centranthus ruber), making it relatively easy to find and record this small species. The galls create red curled edges to the leaves as shown in the photo.

Trioza centranthi is a historically rare and scattered species that has been increasing in recent years, primarily on the south coast of England. It was first recorded in Wales in 2018, and is now becoming widespread, with records along the coast and (increasingly) inland. It would be very interesting to discover if the species is more evenly distributed in Wales than the current distribution map would indicate. You can view the 1km density map for SEWBReC here and the 10km Wales wide distribution here. We have just 82 records for the species at SEWBReC. More information and photos are available from British Bugs.

You may want to use the Aderyn distribution map of Red Valerian as a guide when looking for galls - please also record this host plant if your hunt is successful. You can find photos and information for Red Valerian on Naturespot.

If you spot Trioza centranthi galls during May (or at any other time of year), please send us the record, ideally via SEWBReCORD or the LERC Wales App. Instructions on how to submit records are available here.