EENY-050/IN207: Bumble Bees of Florida

The Featured Creatures collection provides in-depth profiles of insects, nematodes, arachnids and other organisms relevant to Florida. These profiles are intended for the use of interested laypersons with some knowledge of biology as well as academic audiences.

Introduction

This publication is a general guide to field identification, species description, and biology of the five bumble bee species (Bombus spp.) found in Florida. This guide to bumble bee identification in Florida would also be usable for coastal South Carolina, Georgia, Alabama, Louisiana, Mississippi, and Arkansas. However, it is not comprehensive for the northern/mountainous parts of those states where Bombus auricomus, Bombus citrinus, Bombus fervidus, Bombus flavidus, Bombus perplexus, Bombus sandersoni, Bombus terricola, and Bombus vagans can occur.

Distribution

All five bumble bee species found in Florida range as far north in the United States as the Great Lakes region, where other bumble bee species can also be found (Laverty and Harder 1988). In North America, bumble bee diversity is highest in more northern, temperate, and montane (higher elevation) areas and declines from north to south (Williams et al. 2014). In Florida specifically, there are only five species, all of which can be found in the northern part of the state. Species diversity declines moving south in Florida.

Bombus bimaculatus (Two-spotted bumble bee) female. — Figure 1. *Bombus bimaculatus* (Two-spotted bumble bee) female.
Credit: Joel Neylon

Biology and Life Cycle

The life cycle of a bumble bee colony in Florida generally begins in late winter or early spring (late January through March) when new queens search out a nest site for the year. A nest is typically something that has been lived in by another animal previously. Common nest locations include underground cavities such as old mouse nests or rodent burrows, aboveground cavities such as bird houses or crevices by the foundations of buildings, or on the surface of the ground in dense grass (Mitchell 1962; Morse 1982). All five species in Florida typically nest at or below ground, but each species has unique preferences for nest sites. Bombus pensylvanicus tends to nest at the surface of the ground or slightly below ground while Bombus fraternus and Bombus impatiens almost always nest underground (sometimes deep) (Medlar and Carney 1963; Williams et al. 2014). Bombus bimaculatus usually nests underground but has been recorded aboveground in buildings, and Bombus griseocollis will nest on the surface, underground, or aboveground, and is frequently recorded nesting in buildings or bird houses (Medlar and Carney 1963; Williams et al. 2014).

After she selects a nest site, the queen will secrete wax from her abdomen and make the cells for the first workers, who are also females. Her time is then divided between incubating the young and foraging for flowers from which she gathers pollen and nectar while she waits for her first workers to hatch. Once her workers have emerged, the queen will stay in the nest while the workers do all the work outside of the nest including foraging. The queen will continue to lay worker eggs until later in the season (late summer/fall), when she switches first to laying male eggs, and finally to laying eggs that will hatch new queens. The new queens spend their early days eating nectar and pollen to fatten for hibernation, then mate with a male, and finally leave the hive to search for a suitable location to hibernate for the winter (generally in loose soil like compost, mole hills, or well-drained slopes). Newly mated queens will be the only members of a bumble bee colony to survive winter. The old queen and all the males and workers die by late fall/early winter (Mitchell 1962; Morse 1982). Bumble bees in Florida still generally follow this yearly cycle, though the Florida “winter” is very short, and bumble bees can be seen foraging nearly year-round, with males particularly active in late fall/early winter and new queens active in late winter/early spring.

Bombus impatiens (common eastern bumble bee) entering the nest. — Figure 2. *Bombus impatiens* (common eastern bumble bee) entering the nest.
Credit: Joel Neylon

Identifying Bumble Bees

Bumble bees in Florida can generally be distinguished and identified to species level with clear photographs from the field. If you spot one, take a moment to snap a few photos at different angles and upload them to www.inaturalist.org, where they will be identified and included in extensive range maps, useful to researchers studying bumble bees.

Try to get shots that include a clear view of the abdomen and the top of the thorax. Because of the positioning of bumble bee wings, shooting from a side angle usually provides the clearest view of the bee’s abdomen. All Florida Bombus species may be identified with a single photo; however, it is advisable when you are first starting to take several photos until you have a sense of the important marks that will allow identification of species.

A note on size: Bombus size is quite variable depending on caste and time of year. Queens are the largest bees; early season workers (spring workers) tend to be smaller than queens and late season workers (summer and fall workers). Because of the variability, size is generally not a good field mark to rely on for Bombus ID.

Body parts of a bumble bee (Bombus pensylvanicus is pictured). — Figure 3. Body parts of a bumble bee (*Bombus pensylvanicus* is pictured).
Credit: Joel Neylon

Description of Florida Bumble Bee Species

T = tergite (1–7), F = flagellomere (1–11). See Figure 3 for reference to body parts.

Subgenus Pyrobombus

Bombus (Pyrobombus) bimaculatus (two-spotted bumble bee)

Distribution

Found throughout the northern two-thirds of the state, though not as common as other species.

Female

Yellow vertex, long uneven hair, dark wings, distinct black spot on the scutum. T1 yellow followed by two variable sized patches of yellow hair on T2 typically confined to the middle of the segment. T3-6 black. Can be mistaken for Bombus impatiens queens or for Bombus griseocollis workers/queens. Size: queen 18–22 mm (~3/4–1 in); worker 10–16 mm (~3/8–5/8 in) (Schuh et al. 2010).

Male

Yellow face and vertex, long hair, smoky wings. Typically shows distinct black spot on scutum, but this can be reduced or absent. T1 yellow; T2 yellow with black hairs in the lower corners (these dark spots on T2 are the “two spots” referenced in the name); T3 typically black, sometimes with yellow laterally but very rarely completely yellow; T4 often yellow; T5 sometimes yellow; T6/7 rarely yellow. Reasonably distinct. Size: 12–15 mm (~1/2–5/8 in) (Schuh et al. 2010).

Bombus (Pyrobombus) impatiens (common eastern bumble bee)

Distribution

One of the two most common bumble bee species in Florida, the other being Bombus pensylvanicus. Primarily seen in the northern two-thirds of the state, but it has been found in the southern portion as well.

Females

Yellow vertex, short hair, scutum yellow with black hairs intermixed throughout in workers and a narrow black slit in the middle for queens. Queens have darker wings while workers have clear wings. T1 yellow, T2–6 black. Reasonably distinct, but queens may be mistaken for Bombus bimaculatus. Size: queens 21–23 mm (~1–1¼ in); workers 9–14 mm (~3/8–5/8 in) (Schuh et al. 2010).

Males

The same as female workers, but with yellow on the face. Size: 12–14 mm (~1/2–5/8 in) (Schuh et al. 2010).

Rare Variants

Queens, workers, and males occasionally can show yellow, red, or white on T2–6 due to damage at the larval stage. Damage like this can show in other Bombus species, but it is most commonly reported in Bombus impatiens.

Female (left) and male (right) Bombus impatiens. — Figure 6. Female (left) and male (right) *Bombus impatiens.*
Credit: Joel Neylon

Distribution of Bombus impatiens in Florida. Data points taken from GBIF using iNaturalist records (all verified by Joel Neylon or John Ascher) and retrieved on 5/1/24. — Figure 7. Distribution of *Bombus impatiens* in Florida. Data points taken from GBIF using iNaturalist records (all verified by Joel Neylon or John Ascher) and retrieved on 5/1/24.
Credit: © OpenStreetMap contributors with data available under the Open Database License. https://doi.org/10.15468/dl.jxmq5k

Subgenus Cullumanobombus

Bombus (Cullumanobombus) fraternus (southern plains bumble bee)

Distribution

Generally uncommon in Florida. Most recent records are from the Panhandle of the state, though there are records from the northern half of the Peninsula as well.