Orange-belted bumblebee

Description

Bombus ternarius, commonly known as the orange-belted bumblebee or tricolored bumblebee, is a yellow, orange and black bumblebee. It is a ground-nesting social insect whose colony cycle lasts only one season, common throughout the northeastern United States and much of Canada. The orange-belted bumblebee forages on Rubus, goldenrods, Vaccinium, and milkweeds found throughout the colony's range. Like many other members of the genus, Bombus ternarius exhibits complex social structure with a reproductive queen caste and a multitude of sister workers with labor such as foraging, nursing, and nest maintenance divided among the subordinates. B. ternarius is a small, fairly slender bumblebee. The queen is 17–19 mm long and the breadth of the abdomen is 8.5–9 mm. The workers are 8–13 mm (0.31–0.51 in), and the drones are 9.5–13 mm in length. Both the worker and the drone have abdomens about 4.5–5.5 mm (0.18–0.22 in) in breadth. The queen and workers have black heads, with a few pale yellow hairs. The anterior and posterior thorax and the first and fourth abdominal segments are yellow, abdominal segments 2 to 3 are orange, and the terminal segments are black. The queen and the workers are close in resemblance, and the most striking difference between them is in the size of their fat deposits. Workers have very little fat, particularly in their abdomen, leaving plenty of room for the honey stomach, an enlargement of the oesophagus in which nectar can be stored on foraging trips. In contrast, in young queens, the abdomen is largely full of fat. This leads to queens being heavier for their size than workers. In late April, the queen comes out of hibernation from under a few inches of loose soil or leaf litter, and begins to search for a nesting site. Bombus ternarius prefer to nest underground in small and shallow cavities like rodent burrows or natural crevices. She flies low to the ground, stopping often to investigate holes in the earth, and once a satisfactory nest site is found, she forages for pollen and nectar to support her future offspring. Next, the queen secretes a protective waxy coating and builds a grove where she lays fertilized eggs destined to be the first of the new workers. The queen straddles the eggs, allowing for close contact between the ventral surface of her abdomen and thorax and the eggs. This close contact allows the queen to incubate her brood with the heat she generates by pulsing contractions in her abdomen.