|scientific name Megachile |
common name Leafcutter bees
Various niches (burrow, natural cavity, ground) near food source / cover (Medler & Lussenhop 1968).
Males emerge first. Flight period varies with temperature and is specie specific. (Richards 1984).
The body is black, robust and non-metallic. Large cheeks and mouth mandibles have 3 to 5 tooth projections. The maxillae and labrum of both sexes form an extensible proboscis “tongue-like” structure used to feed on nectar. The first abdominal segment is fused to the metathroax (last thorax segment) forming a propodem (thorax appears to have 4 segments vs. 3) (Medler & Lussenhop 1968). Arolium (sack-like structures between the claws) are not present (Mitchell 1962). The basal tergum (dorsal abdomen segments) concave anterior, the scutellum (behind the scutum on the dorsal mesothorax segment) is broad, maxillary palpi with 3 segments (Medler & Lussenhop 1968).
Female: The mouth mandibles are with 4 or 5 tooth projections (Michener 2000). Antennae have 12 segments. There is a pollen-carrying structure (scopa) located on the ventral abdomen region, which is densely covered with hair. There are no functional pollen-collecting hairs on the legs. There are 6 abdominal segments (Medler & Lussenhop 1968).
Males: There is a pronounced basal and submedian process on the lower margins of the mandibles. The front coxae (upper leg segments) often with spines and front legs can be broadly expanded with bright colours (Michener 2000). Antennae have 13 segments. Males have poorly developed pollen and nectar collecting morphological structures and therefore do not contribute to provisioning of the young. There are 7 abdominal segments (Medler & Lussenhop 1968).
There are 115 species of leafcutter bees in North America with 22 species recorded in Western Canada. The leafcutter bee is a solitary insect, where some species have been recorded to show gregarious nesting behaviour. However, each female constructs her own nest and provisions it and has little interaction with nearby females. (Richards 1984). There is complete metamorphism (egg, larva, pupa, adult) with overwintering fully developed larva in diapause (prepupa) (Medler & Lussenhop 1968). The mother bee constructs a series of cells using leaf pieces or petals (Richards 1984, Krombein et al. 1979), separating each cell with either leave pieces, chewed wood, dirt, etc. or a combination of material (Medler & Lussenhop 1968). Not all species construct a single linear row of cells, but may have several cells in near approximation of one another (Hobbs 1956). The cell structure comprises of a smooth concave posterior wall (toward end of borer) and a rough convex anterior inner surface (towards the nest entrance). This feature allows the larvae to orient themselves to face the entrance. The mother bee places provisioning in each cell, lays a single egg per cell and the caps off the openings. The larvae hatch from the egg and feed on the pollen-nectar mass and proceed through a given number of larval stages (approximately 1 month). The completely mature larval stage pupates and once development is complete, the adult escapes the pupa. The adult will remain in the cell until the wings are expanded and the integument is hardened. Because there is a time lapse between when the first egg is laid and enclosed within its pupa, the mother bee takes advantage of varying larval development. Inner cell larvae development is slower and males pupate 1 – 2 days sooner and the pupal stage is 2-4 days sooner then the females. Therefore, male eggs are laid in the outer cells (emerge earlier) and female eggs are laid in the inner cells (emerge later) (Medler & Lussenhop 1968).
Destruction of nesting habitat has decreased populations of some native species (Richards 1984).
Usually polylectic (collects pollen from wide range of flowering plants). Forages on pollen and nectar, as well as provisioning with pollen and nectar (Medler & Lussenhop 1968).
Cosmopolitan (Mitchell 1962).
Comments are published according to our submission guidelines. The EH Strickland Entomological Museum does not necessarily endorse the views expressed.