The two-spotted bumble bee (Bombus bimaculatus) is a species of social bumble bee found in the eastern half of the United States and the adjacent south-eastern part of Canada. In older literature this bee is often referred to as Bremus bimaculatus, Bremus being a synonym for Bombus. The bee's common name comes from the two yellow spots on its abdomen. Unlike many of the other species of bee in the genus Bombus, B. bimaculatus is not on the decline, but instead is very stable. They are abundant pollinators that forage at a variety of plants.
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TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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Not a migrantAnimals that do not make seasonal movements and stay in their native home ranges all year round are called not migrants or residents.
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starts withBombus bimaculatus was first described by Ezra Townsend Cresson, an American entomologist, in 1863.
Workers look very similar to queens, with the two mainly distinguished by size. Sometimes large workers can be mistaken for small queens, especially toward the end of the season when workers have grown larger and new queens emerge. Queens have a black face with a triangular patch of yellow hairs on the vertex. Their thorax is yellow except for a shining area on the disc that is bordered by black hairs. Their venter is black with some yellow hairs on the legs.
Male faces have intermixed black and yellow hairs. They resemble females in most markings, except their tergite 2 has more yellow lateral hairs than the female whose tergite 2 has black edges and few yellow lateral hairs.
The size of the radial cell in the wing differs for each. Workers have the smallest, ranging from 2.5 to 3.6 mm. Males are slightly bigger at 2.6–3.6 mm. Queens have the largest at 3.4–4.1 mm.
B. bimaculatus is mainly found in eastern temperate forest regions throughout the United States and the southeastern part of Canada. It can also live in the coastal plains of the southeastern United States, the eastern Boreal forest, and the eastern Great Plains.
This bee lives in underground nests, preferably in or around wooden areas and gardens. Nests can be anywhere from 6 inches to a foot below the surface. Tunnels traveling to the nest range from 9 inches to 4 feet long. B. bimaculatus can also nest above ground or in cavities. Bees do not build nests and instead rely on finding abandoned rodent dens, hollow logs, suitable man-made structures, or tussocks. Queens will hibernate in loose dirt or rotting logs.
This bumble bee is very common and has been experiencing steady growth unlike many other bumble bees that are in decline.
B. bimaculatus queens forage on Aquilegia flowers. The queens hang upside down on stamens, clutch the filament with their forelegs, and scrape off pollen using their middle and hind legs. Workers enter the Aquilegia spurs by pushing their head and part of their thorax into the spur's mouth. They then extend the maxillae and tongue into the spur to drink nectar, repeating this process on multiple spurs of the same plant before visiting the next one.
B. bimaculatus queens' probosces range from 10.53 to 12.19 mm in length, which has little overlap with other Bombus species. This may potentially be the reason why B. bimaculatus are such abundant pollinators.
Research comparing B. bimaculatus to Xylocopa virginica, a carpenter bee, found that the former learned faster and had more flexible foraging patterns. It was hypothesized that B. bimaculatus being a social bee could have individuals specialize in either foraging for nectar or pollen, instead of having to worry about both in overall food collection as the nonsocial carpenter bees needed to do.
Bumble bees eat nectar and pollen from plants. B. bimaculatus is known to pollinate a wide variety of plants, but they seem to have favorites. Queens can be found on willow and plum. Workers are found on red clover and mint. Males are found on mint and sweet clover.
As a species they have been found foraging at the following plants:
B. bimaculatus mate outside the nest with males patrolling in circuits, searching for a queen to mate with. Most queens only mate once; however, there are some queens who mate multiple times and have offspring of multiple paternity.
