Colorado Insects of Interest
Scientific Name: Bombus species
Order: Hymenoptera (Bees, Wasps, Ants, Sawflies and Relatives)
Family/Subfamily: Apidae/Bombinae (Bees/Bumble Bees)
Distribution in Colorado: At least one of the 23 species of bumble bees (Table 1) present in Colorado can be found any where in the state. Among those that have the widest range within Colorado are Bombus huntii, B. appositus, B. morrisoni, and B. nevadensis. Several are found primarily at higher elevations, including Bombus balteatus, B. bifarius, B. centralis, B. melanopygus, B. rufocinctus, B. sylvicola.
Life History and Habits: Bumble bees are social insects that establish colonies which last through a growing season. Colonies are initiated in spring by an overwintered and previously fertilized female, known as the queen. As the colony develops and expands it may ultimately be populated over 100 individuals that are organized into different castes. Dominating are infertile females, known as workers. By midsummer some males are usually produced along with some large females, which will serve as potential queens of the following season. The original queen, along with all workers and males perish at the end of the year.
Within the colony, rearing and food storage occurs in roundish wax pots that are spread throughout the nest space. The wax produced from abdominal glands by the bees and the jug-like cells are often being reformed to meet colony needs. Eggs are laid in these wax pots and the larvae develop within them, being fed and tended by adult bees. When full-grown the larvae cap over the rearing cell with silk and pupate, later emerging as a winged adult.
Nectar and pollen serve as the foods that sustain the bumble bee colony and forager bees collect the pollen on the hind legs, in specialized pollen baskets, similar to honey bees and digger bees (Family Apidae). Excess food will be stored for later use but bumble bees do not produce large amounts of honey (processed nectar) and ultimately use all food that is collected.
As the colony develops through the season several changes in the colony occur. Originally there is a single queen that is charged with all colony functions - from nest construction to food collection as well as rearing. Subsequently the first workers produced tend to be rather small because of poor diet, and size contrasts markedly from the queen. However, as the workers assist with and take over most colony functions the larvae are increasingly well fed and subsquently develop into larger workers.
Bumble bee females can sting and workers will readily defend a colony if it is disturbed. The sting is quite painful but, unlike honey bee workers, bumble bee stingers do not detach and they are capable of repeated stings.
Bumble bees are very important in providing pollination services to many plants. They have a different approach to pollen collection than do honey bees and most other bees, known as “buzz pollination.” When visiting a flower a bumble bee will often grasp it with its mandibles and vibrate, causing the pollen to be shaken out onto its body. Such pollination style is critical for many native plants which are dependent on bumble bees for pollination and subsequent seed production.
Among the plants that are dependent on buzz-pollination are many plants in the nightshade family (Solanaceae). As a result, bumble bees are used widely in pollination of greenhouse-grown tomatoes and peppers, which are produced commercially in several areas of Colorado.
Cuckoo Bumble Bees: Among the native Colorado species are three cuckoo bumble bees (subgenus Psithyrus). Queens of cuckoo bumble bees enter and displace the queen of existing colonies and the workers then rear the young of the invader. The cuckoo bumble bees are usually distinguished from other bumble bee species by having an abdomen that is less hairy. The most common species, Bombus (Psithyrus) insularis Smith, is also one of the lighter colored species.
|Table 1. A checklist of bumble bee species (Bombus) present in Colorado, arranged by subgenera (in parentheses). Notes on distribution provided by Virginia Scott, University of Colorado.|
|balteatus - high elevation over 10,000 ft|
|auricomis (sometimes considered a subspecies of nevadensis) - Eastern CO|
|nevadensis nevadensis - Our biggest species. Found throughout most of the state roughly 5000-8000 ft|
|occidentalis – formerly common from the Front Range west. Decreased populations of this species have been noted in several western states|
|fraternus - Front Range and eastern Colorado up to about 6500 ft|
|riseocollis - across state at lower elevations (<6000 ft)|
|morrisoni - across state at lower elevations (<6500 ft)|
|ufocinctus – Front Range-west below about 8000 ft|
|fernalde - about 7000-8500 ft|
|insularis - across state (4500-11,000 ft)|
|suckleyi - mountains (6500-10,000 ft)|
|bifarius - mountains (7500-10,000 ft)|
|centralis - mountains (7000-9000 ft)|
|flavifrons - mountains (8500 - >12,000 ft)|
|frigidus - over 10,000 ft|
|huntii - across state 5000-7000 ft, not along eastern edge of state|
|sylvicola - mountains over 10,000 ft|
|melanopygus - mountains roughly 9500-12,000 ft|
|mixtus - mountains roughly 9000-11,000 ft|
|appositus - across state between (roughly) 7500-10,000 ft|
|californicus (sometimes considered a subspecies of fervidus) - 7500-10,000 ft|
|fervidus fervidus - lower elevation 5000-8000 ft|
pensylvanicus - lower elevations, mostly eastern plains up to 6000 ft; valid Moffat and Delta county records
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