Leaf rolling weevil  (Byctiscus populi)

Classified as Rare in Great Britain (3).

This leaf rolling weevil has a shiny metallic upper surface, which varies in colour from bright green to a vibrant coppery red. The underside, legs and elongated snout, known as the 'rostrum' are deep violet-blue to black in colour (2). Males can be distinguished from females as they have two very small spines on their pronotum(2), the function of which is unknown (4).

B. populi is fairly common and widely distributed throughout central-western Europe and is also found in the Mediterranean area, the Nordic countries, Asia Minor, central Asia, Siberia, Mongolia and northern China (3). In Britain the species is currently classified as rare, but was once distributed across most of southern England and up into Norfolk, Worcestershire and east Gloucestershire (3). There are currently only a handful of sites in England (5).

You can view distribution information for this species at the National Biodiversity Network Gateway.

This species feeds and lays its eggs on aspen Populus tremula, and white poplar, Populus alba. Recent studies on the ecology of this species in England and Latvia have shown that it prefers young regenerating aspen under 2.8 meters tall in full sun (4).

Females create thin, tight 'leaf-rolls' from one or two aspen leaves in which 1-4 small white eggs are laid. Leaf-roll construction is an extraordinarily complex behaviour, which can take up to 2 hours of careful nibbling, rostrum stamping, tugging and sealing with anal secretions. Occasionally a male may assist the female and defend her from other amorous males by engaging in fierce battles involving head-to-head wrestling and violent rostrum tapping (4). After hatching, larvae remain in the rolls, which fall to the ground, feeding for around 15 days. They then burrow into the soil to pupate; adults emerge above ground and over-winter, the location of over-wintering is at present unknown.

The decline of this attractive beetle is thought to be due to inappropriate woodland management including the removal of aspen, the loss of sunny glades and the reduction in coppice management (3). The isolation of B. populi populations in an unfavourable landscape may prevent the colonisation of suitable sites (4). Furthermore, larvae inside leaf-rolls that have fallen to the ground are subject to predation, possibly by small mammals and ground beetles (5).

Byctiscus populi is a priority species under the UK Biodiversity Action Plan, which aims to enhance the current population. A number of the sites on which the species occurs are SSSIs (3). English Nature has funded ongoing research into the ecology and conservation of this species. Preliminary results emerging from this research have suggested that areas of aspen occupied by this species should be protected against predation and trampling by humans, and that regenerating aspen should be cut on rotation every 4 years in order to maintain trees of a suitable height. If the UK population does not increase, captive breeding and release programmes may be feasible (5).

There may be further information about this species available via the National Biodiversity Network Gateway.

The UK Biodiversity Action Plan for this species is available at UK BAP.