Colletes cunicularius (Linnaeus,1761)

Synonyms

Apis subterranea LINNAEUS 1758 (nec. L. 1758);  Apis cinerea GEOFFROY 1785 (nec. SCHRANK); Colletes pilosus SPINOLA 1838; Colletes hirtus LEPELETIER 1825;

Description and notes

The largest of the nine British species in the genus, with a population that apparently differs slightly from the Continental race in both morphological and ecological respects. As a result, it has been recognised as a distinct subspecies, C. cunicularius celticus, by O'Toole (1974). More recently, major differences between the Continental and British populations have been found in the chemistry of the Dufour's gland secretions (Albans et al., 1980; Duffield et al., in Bell & Carde, 1984), raising the possibility that the British populations may be specifically distinct.

Distribution

Historically, the species has an unusual distribution, being confined to a number of extensive coastal sand dune systems in north-west England and north-west and south Wales. It is often locally abundant; for example, at Kenfig dunes, West Glamorgan, there have been nesting aggregations of up to 18,000 nests (C O'Toole, pers. obs.). In 2011 a number of inland sites were recorded, with populations in Shropshire, Nottinghamshire and Worcestershire

Status (in Britain only)

Listed as Rare (RDB3) in Shirt (1987) and Falk (1991).

Habitat

Large, mature coastal sand dunes, wherever creeping willow grows. Recent records (2011) also show that the species can be found on sandy heathland and in disused sand pits inland

Flight period

This is the only British Colletes to fly in the spring (early April to the end of May, rarely mid-June), rather than in the summer or autumn.

Pollen collected

The bee is polylectic, but the majority of British records suggest that the females forage for pollen largely on creeping willow (Salix repens). When 40-50% of the male catkins are dehiscing pollen, the bees can be expected to make a mass appearance within two to three days if there is continuous fine weather.  However, at a coastal site on the Wirral peninsula (Merseyside), in April 1996, females of this species were foraging exclusively at Salix cinerea, there being no S. repens present (C. Clee, pers. comm.).

Elsewhere in its range, Müller & Kuhlmann (2008) list Salix (Salicaceae), Cichorioideae (Asteraceae), Aceraceae, Fabaceae, Rosaceae, Ericaceae, Resedaceae, Rhamnaceae, Brassicaceae, Grossulariaceae and Cistaceae based on 44 pollen loads from 27 different localities. and in Slovenia, the species has been observed collecting pollen of Brassica (Brassicaceae) (Gogala, 1999).

In Finland it is reported to be oligolectic, visiting Salix caprea (Salicaceae). Vereecken (in litt.) reports foraging at the same species in south western France. Pekkarinen (1998) lists Salix (Salicaceae) as the pollen source in Finland.

Ornosa & Ortiz-Sánchez (2004), citing other authors, list Salicaceae, Ranunculaceae, Brassicaceae, Rosaceae, Asteraceae and Liliaceae.

Bischoff  et al (2003) state that 40% of all cells analysed contain more than 20% non-Salix pollen. Other pollen sources listed by Bischoff include Sorbus aucuparia, Prunus padus, Prunus laurocerasus, Pyrus sp., Malus sp. (Rosaceae); Quercus sp. (Fagaceae); Sambucus nigra (Caprifoliaceae); Ranunculus sp. (Ranunculaceae); Euonymus europaeus (Celastraceae); Acer sp. (Aceraceae), Ilex aquifolium (Aquifoliaceae). It also visits Pistacia lentiscus in Turkey, and in Italy it has been observed foraging exclusively on Fabaceae.

Vereecken (2004) has shown that males of C. cunicularius are the exclusive pollinator of the sexually deceptive orchids Ophrys exaltata and Ophrys arachntiiformis (Orchidaceae).

Nesting biology

The nest comprises a slightly inclined tunnel, some 45-55 cm deep, with cells built at the ends of side branches. These branches are concentrated in the deepest quarter of the nest, so that the vertical distance between the shallowest and deepest cells is only 4-8 cm. The mass emergence of males (from the upper cells) occurs in the afternoon of the day before mass emergence of females. Like all species of Colletes, C. cunicularius lines its brood cells with a transparent cellophane-like membrane. This is waterproof, resistant to fungal attack and presumably maintains the correct level of humidity during larval development. The source of the membrane is a liquid secretion of the Dufour's gland in the abdomen. The female bee uses her short, bilobed tongue as a kind of paint brush to spread the oily secretion over the internal surface of her cell. It dries to form a clear membrane.

Flowers visited

In addition to creeping willow, both sexes have been observed in South Glamorgan by R Paxton (pers. comm.) visiting dandelion (Taraxacum sp.) flowers, presumably only for nectar. In Brittany, S Roberts has observed both sexes nectaring at blackthorn (Prunus spinosa).

Parasites

In continental Europe, the species is parastised by Sphecodes albilabris (Westrich, 1989; Söderman & Leinonen, 2003).

Author of profile

G R Else, J P Field and C O'Toole.

Year profile last updated

Profile written: 1999

Proofed & updated in January 2012