Psylliodes (Psylliodes) attenuata

Psylliodes (Psylliodes) attenuata (Koch, 1803) Diagnosis Psylliodes attenuata is 1.6-2.6 mm long (Figs 1, 2) and can be recognised as belonging to genus Psylliodes by its jumping hind legs and antennae with ten antennomeres (Fig. 1 a, b). It can be distinguished from other North American Psylliodes by its green-bronze dorsal colouration (translucent and paler at elytral apices); head with antennal calli present and defined by grooves posterad (Fig. 1 c, forming an ‘ x’ together with grooves below calli), without puncture-like central pit at centre of the ‘ x’. Additionally, male only characters which can be used for confirmation include: protarsus with basal segment widest before apex (Fig. 1 e, apical 3 / 4); abdominal ventrite V with median quarter of posterior edge elongate (Fig. 1 d) and flexed dorsally posterad; aedeagus widest at basal third with apex attenuate (Fig. 2 b). Distribution We recorded Psylliodes attenuata from the eight illustrated localities in Canada (Fig. 3). Specimen data are available via GBIF. org in Douglas (2024). Surveys further to the southwest in Ontario by JR at hop yards near Tavistock (Wellington County) and Aylmer (Elgin County) did not result in captures of P. attenuata specimens. Biology The finding of 752 specimens from eight sites separated by at least 750 km indicates that multiple breeding populations of P. attenuata are established in Canada. Like many flea beetles, P. attenuata are univoltine, with egg laying and below-ground development of immatures during summer. New adults emerge in August and September in UK and then overwinter in vegetation, litter and soil (Cox 2007). Adults are fully winged and have been collected in UK from March to September, with most in May, August and September (Cox 2007). Feeding damage to hop plants We observed substantial damage to some of the assessed hop yards (Fig. 4). Growers reported that new hop shoots were severely defoliated by overwintering adult beetles in May, stunting growth for up to 1 week on some varieties. Given the rapid growth of the plants and the departure of the overwintering adults during June, damage became less noticeable during July. Additional damage became evident in mid-August following the emergence of a new cohort of adult beetles. Damage levels increased up to harvest time. Beetles attacked mainly lateral shoots, flowers and fruiting bodies (cones) during August and September. In some hop yards, approximately one in three cones contained a feeding flea beetle. Cones with extensive feeding damage desiccated and turned brown (Fig. 4 f). This appeared similar to symptoms of caused by downy mildew (Podosphaera macularis), except that beetle-feeding also causes holes in plant tissue. Growers estimated yield losses of at least at 10-15 % in heavily infested hop yards. Notes The external morphology and male genitalia of the Canadian specimens closely matched taxon concepts of P. attenuata. Specimens were confirmed as P. attenuata using Mohr (1966) and Rheinheimer and Hassler (2018) and in comparison with specimens from the Canadian National Collection of Insects Arachnids and Nematodes (CNCI) identified by L. H. Woollat (UK) and M. Döberl (Germany) and the United States National Museum (USNM) identified by F. Heikertinger. As the only bronze-coloured Psylliodes with a complete ‘ x’ shaped impression on the frons (Fig. 1 c, Fig. 1 a, b) and no frontal pit, P. attenuata is unlikely to be confused with any other North American species. DNA Barcoding Results Analysis of the two DNA-barcoded Canadian specimens of Psylliodes through the BOLD Identification Engine resulted in a 100 % match with P. attenuata for one specimen. This specimen shared a BOLD Barcode Index Number (BIN, Ratnasingham and Hebert (2013)) with a specimen from Germany (BIN ACJ 8391) and the other formed its own neighbouring BIN (AFE 7531). Comparison of sequences of our specimens to the available Psylliodes specimens from barcoding initiatives (Hendrich et al. 2014, Pentinsaari et al. 2014) indicated sequence divergences of 0–3.5 % amongst 60 public and non-public records in BIN ACJ 8391. The morphological identification of these specimens as P. attenuata, their presence on hops plants and the finding that one of two DNA barcoded specimens exactly matched the sequence of a specimen from Germany all support the conclusion that the Canadian specimens are P. attenuata.

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