Crawfordapis luctuosa is a large, ground-nesting bee found in Central America.These bees belong to the Colletidae family and Diphaglossinae subfamily, the subfamily being limited to the New World (Hanson & Gauld 1995). They eat nectar and pollen, and have been documented to use pollen from a great variety of plants.Females dig nests on exposed or lightly vegetation-covered soils, laying eggs and raising larvae in cells within the nest tunnels.
C. luctuosa has been found from Chiapas, Mexico to western Panamá (Roubik & Michener 1984). The species has been studied primarily at at elevations from 1540 m to 1680 m in sites near Monteverde, Costa Rica (Otis et al. 1982), and in Chiriquí Province, Panamá (Roubik & Michener 1984).
The bees are found nesting in montane areas, in areas of exposed soil or with low grass cover, surrounded by cloud forest or elfin forest (Roubik & Michener 1984, Otis et al. 1982).In these sites, aggregations of tens to hundreds of nests are found on the flat ground or in angled banks (Roubik & Michener 1984).
The species lives on nectar and pollen and is polylectic, meaning that it collects pollen from a great variety of plants. Roubik and Michener (1984) found pollen from over 60 species of plants in 30 C. luctuosa nest cells, including up to 10 different species of pollen in an individual cell.These bees participate in buzz pollination, and in the pollen collected by Roubik and Michener (1984), there was a predominance of pollens from Melastomataceae and other buzz-pollinated plants. Wuellner and Jang (1996) found that the provisions in nests were a viscous liquid composed of nectar and pollen.
At a nesting aggregation in Panama, three Tetraonyx cyanipennis beetle larvae were found living in nest cells of C. luctuosa, and two adults of the same beetle species were found in occupied nest cells.Other bees (of the genera Thygater and Colletes) also nested in small numbers in the area of the C. luctuosa nesting aggregation, and an adult male Ptiloglossa mexicana bee was found in a C. luctuosa nest, suggesting possible usurpation of nests by other bee species (Roubik & Michener 1984).
C. luctuosa are a large, short-tongued (Wuellner & Jang 1996) bee with a black body, dark wings, and dense black hairs covering most of the body, with the exception of reddish hairs found on the posterior metasoma (Hanson & Gauld 1995).Individuals can be as long as 24 mm (Otis et al. 1982).
Upon leaving their nests, some female C. luctuosa individuals will show orientation flight behavior, hovering near her nest entrance then flying away in a spiraling pattern away from the nest in order to orient herself and become familiar with the area—this behavior was most frequent after alteration of the nest area, and early in the day when individuals made their first exits from the nests.When returning to the nest, females often circle their nest, spiraling inward, oscillating near the nest entrance, and then flying in (Wuellner & Jang 1996).Females will leave their nests to go on foraging trips, visiting their foodplants and returning with pollen and nectar to provision their nests (Otis et al. 1982, Wuellner & Jang 1996).Females have been observed to make very short visits to nests, remaining inside less than a minute, which are likely only exploratory visits; longer visits called “working visits” may indicate provisioning the nest, digging, or other behaviors (Otis et al. 1982). Females are most active in their provisioning behaviors (going to collect pollen, returning for working visits) between 5:00 am and 10:00 am, with activity continuing but at a decreased rate into the afternoon (Wuellner & Jang 1996).Females that are actively provisioning their nests show high nest fidelity, consistently returning to the same nest to bring pollen and nectar to their eggs and larvae.Nonprovisioning bees have been observed performing “floating” behaviors, in which females fly in oscillating patterns close to the ground over the nest aggregation, entering multiple nests for just a few seconds each (Jang et al. 1996).It has been hypothesized that females entering nests other than their own may be usurping nests, stealing provisions, or looking for a new nest (Otis et al. 1982; Roubik & Michener 1984; Jang et al. 1996).Few studies have thoroughly investigated these hypotheses, but Jang et al. (1996) recorded at least one female making the transition from floating behavior to provisioning by establishing herself in an unoccupied nest within the study plot.
Males never enter the nests after their emergence as adults, and are observed only flying in sinuous courses 0.1 m to 2 m from the ground near the nesting aggregations (Roubik & Michener 1984; Wuellner & Jang 1996).
Despite the fact that they do not enter nests, males will fly over the nesting aggregation when females are active, chasing them and other flying objects in the area (Otis et al. 1982; Wuellner & Jang 1996), and have been observed to fly in irregular courses over limited areas—though other males flew in the same areas, so this was not an indicator of any territoriality (Roubik & Michener 1984; Wuellner & Jang 1996).One mating has been observed and recorded by Roubik & Michener (1984), lasting 65 seconds.In this instance, the male mounted the female on the ground and in the last 20 s, the female attempted to dislodge the male by crawling away; the male reared back and then detached his genitalia from the female.
Solitary females dig tunneled nests with round openings at ground level from 10-12 mm in diameter (Roubik & Michener 1984).Nest tunnels have been documented to extend into the soil anywhere from 22-120 cm (Otis et al. 1982, Roubik & Michener 1984).These nest tunnels contain cells branched off from the main tunnel in which the females lay their eggs and deposit pollen to feed larvae.Number of cells per nest varies, and cell size ranges from 33 to 38 mm long and 11 to 13 mm in diameter (Roubik & Michener 1984). Males do not enter the nests, and it is not known where the males spend the night (Wuellner & Jang 1996).
