Hoplia philanthus Fuessly, 1775

Widely distributed throughout England with several records from Scotland north to Perthshire (NBN). Of local occurence but may be very common where found, in a given locality some years will produce an abundance while in others they are very few. During 2007 we were fortunate in finding the adults swarming in bright sunshine over long grass either side of a busy pathway in Cassiobury park , the swarm covered an area some 60m square and we estimated about a hundred specimens were active at any given time; many were in flight while others sat upon grass flowers, all the while specimens alighting and taking flight. This gave us the opportunity to examine a large number of specimens and, using leg colour as a guide, we were unable to find a single female. The next day, also hot, there were none active, unfortunately we were unable to visit during the following week so cannot say whether this behaviour continued. They are also occasionally seen on flowers especially Rubus, throughout the Watford area, typically during June and July but they occur as early as May (Jessop).

Adults typically emerge around mid-June and males swarm over herbage or grass searching for females. Eggs are laid in the ground in midsummer and larvae feed on roots in the autumn and spring before pupating in earthen cells in late spring. The life cycle is completed in a single year (Gratwick, 1992).

Head, pronotum and scutellum black, coarsely punctate with small white scales although along the base of the pronotum some are blue as are the underside scales. Antennae, head in front of eyes and lateral margins of pronotum with stout setae. Front margin of clypeus strongly raised. Pronotum widest at middle, narrowed anteriorly and posteriorly, hind margin strongly sinuate. Elytra quadrate, shining red or variously darkened, depressed inside humeral prominences and with white scales often patchily arranged. Pygidium and propygidium exposed. Legs stout; protibiae with 3 prominent teeth on outer side, meso and metatibiae with short spines throughout. Femora and tibiae with sparse blue scaling among the orange spines. Tarsi 5-5-5, segments 1-4 ringed with very short spines apically, last segment long and incurved. Pro and mesotarsi with 2 incurved claws, the outer about half the length of the inner, all longitudinally divided at tip. Hind tarsus with a single long incurved claw longitudinally divided at tip, this character separates Hoplia from all other British scaraboidea. Antennae and legs black in male, red in female (Britton)

During the hot sunny afternoon of 29th June 2008 another extensive swarm was seen in Cassiobury park, this included the same area of long grass occupied by the 2007 swarm but also covered a much larger area, perhaps a hundred metres square, which included several exposed chalky-soil pathways worn through the long grass by pedestrian traffic, on these pathways several dead Hoplia were seen, presumably trodden underfoot. This was very likely the first day of swarming as the area is inspected several times each week and the long grass was swept the previous day. Unlike the 2007 swarm this contained a good proportion of females and several mating pairs were observed.

This was only a hundred metres or so from where the nocturnal Serica was found swarming during 2006.

Description from 4 Watford specimens at X20