Bombus impatiens

The bees of B. impatiens are similar to those of B. bimaculatus, B. perplexus, B. vagans, B. sandersoni, and B. separatus in their appearance.[4][10] They have short and even hair, medium-sized heads with cheeks that are similar in width to their heads, and a long and rectangular body.[4] In general, queens and workers are similar in their coloring, pubescence, and structure.[6] However, with a body length of 17–23 mm, queens have bigger bodies than males or workers. Workers have bodies that are 8.5–16 mm, and males have bodies that are 12–18 mm long.[4][6] The differences in their sizes can be observed by the differences in their larval weight at second instar.[8] In addition to the difference in their sizes, males slightly differ in their coloring. While queens and workers are both black with a yellow thorax and first abdominal segment, males have a yellow face and head.[10]

Inside the nest, the worker bees distribute themselves in a non-random fashion to be a certain distance away from the center of the nest. By doing so they increase their efficiency, as the distance traveled between tasks is minimized. The tasks of some workers are related to their space in the nest. The labor for the workers is divided according to their body sizes. They vary in size, and the smaller bees are usually found near the center of the nest with the job of feeding the larvae whereas the bigger workers are usually found at the periphery, working as foragers and as guards. In general, they keep their spatial pattern as well as their jobs throughout their lifetime.[11]

Worker bees are totipotent and have the ability to lay eggs, and a few workers even have mature oocytes in their ovaries. However, when there is a queen in the colony, the workers do not attempt to lay eggs or develop eggs. They usually do not show aggression towards other workers or the queen, showing no “competition phase.” Without a queen, aggression is more common.[8]

Queen and drone mating

A gyne mates with a male bee near the end of the hive's life cycle. They rest on the ground or on vegetation in order to mate and the mating lasts from 10 to 80 minutes. In order to increase the probability of his genes getting passed down safely, the male mates for a certain amount of time to let his sperm harden during mating. Soon thereafter the gynes hibernate. The following spring they emerge from hibernation and set about to get strong on nectar and to find a suitable old mouse or chipmunk hole to begin a colony. The first thing she builds is a honeypot, then she fills it with food (nectar/pollen), making it easier to feed her new brood, which are raised in paper cells she builds. The queens lay about 2000 eggs in one season, but only half of them will survive to become full adults.[5]

Foragers of B. impatiens colonies use a strategy called traplining, in which the bees visit their food sources in a repeatable sequence, to improve their efficiency, especially in an unfamiliar environment.[16] The bees establish traplines by searching among flowers in an orderly manner. Upon establishment, the traplines remain stable for long periods of time.[17] Traplining has many advantages. The bees can minimize both the distance traveled by linking the sources in a more direct path and the time spent searching by knowing the locations of food sources.[18] Also, the bees can travel through the locations that were recently depleted of their resources, saving their energy and time.[16]

B. impatiens use communication in order to maximize the benefit of foraging. The bees become faster and more accurate as they become more experienced at foraging,[19][20] and the returning foragers tend to stimulate the foraging activity of the colony.[21] The foragers of B. impatiens improve their foraging activity by communicating with others in their nests. They share their abilities to associate scents of good food sources.[16]

There are many food plants for B. impatiens including: “Aster”, Cirsium, Eupatorium, Gelsemium, Malus, Pontederia, Rubus, Solidago, Trifolium, Crocus, Pieris, Rhododendron, barberry, mountain laurel, rose, clover, purple vetch, pickerel weed, purple loosestrife, buttonbush, Beggar’s ticks, goldenrod, boneset, burdock, and Impatiens from which the bee's name may come.[4][10] The bees can eat the raw materials like pollen and nectar of the flowers but most bees in the colony eat honey that is made using the raw materials since it has higher nutritional value. To create honey, the bees consume the pollen and the nectar, and then regurgitate them, mixing them with enzymes in their stomachs.[5]

Bombus impatiens are hosts to other bees. Ps. Laborious and Bombus citrinus are some examples of parasites.[10] Also, Entromopox-like viruses and prokaryotes called Spiroplasmataceae have been found in the workers. However, there is no known harmful effect to B. impatiens.[22][23]