R.W. Thorp’s unpublished surveys have revealed that, since 1998, the populations have decreased to the point of being not seen at all in 2004 or 2005, with only one individual found in 2006. Because extensive surveys of the area within which B. franklini exists have, as of 2006, uncovered only one individual, but similar surveys in the first three years (1998-2000) uncovered individuals at many historic and seven new sites, it can be concluded that the extent of population is decreasing severely. Though further investigation would be required to determine the exact number of extant B. franklini, based on their limited range, it can be assumed that their populations are decreasing to dangerously low levels, and therefore need protection, which it has not yet legally received.

Bombus franklini occurs only in the USA. It is found only from southern Oregon to northern California between the Coast and Sierra-Cascade Ranges, in Douglas, Jackson and Josephine and Siskiyou and Trinity counties in Oregon and California respectively. This area is around 190 miles in the north-south direction (40º58’ to 43º30’N latitude) and 70 miles from east to west (122º to 124ºW longitude).

The population is currently decreasing drastically. Dr R.W. Thorp’s unpublished surveys have revealed that, since 1998, the populations have decreased drastically, and no individuals were found at all in 2004. Surveys of many historic and potential sites within the area inhabited by these bumblebees were repeated annually over nine years. Between nine and seventeen historic sites were visited annually. Some were visited more than once for an average of visits of historic sites per year. In addition, six to nineteen potential sites were visited at least once each year. During the first three years, bees were observed at seven new sites (where this bee had not been recorded before) but as time went on this number decreased. The continued abundance of other bumblebee species suggests that the habitat has not recently become uninhabitable.

The habitat of B. franklini includes floral resources, such as Lupinus, Eschscholzia, Agastache, Monardella and Vicia, and abandoned rodent burrows that are thought to be used for nesting. Bumblebees are social insects; they live in colonies. Most make their homes in abandoned animal burrows or in grassy tussocks, and feed on both the nectar and pollen rewards offered by the flowers of the plants they pollinate. Bumblebees have a special technique in foraging that makes them exclusive pollinators of certain plants. They engage in “buzz pollination” by which they sonicate the flowers to vibrate the pollen loose from the anthers.  Tomatoes and related plants (Solanaceae), blueberries (Ericaceae), and others are pollinated this way.

The use of commercial bumblebee colonies in greenhouses to pollinate crops such as tomatoes, peppers and some field crops such as highbush blueberries has had an impact on bumblebee populations as exotic diseases are introduced into populations of native bee species. The commercialization of bumblebees in North America over the past two decades is thought to have caused a pathogen spillover that has devastated local, wild populations of the same and some other species. These pathogens include tracheal mites (Locustacarus buchneri) and intestinal protozoa (Crithidia bombi, Nosema bombi), which can be transferred from bumblebee to bumblebee via the flowers upon which they feed, or within the colony. Although these pathogens are not necessarily lethal because they don’t directly kill their hosts, they reduce the bumblebees’ ability to learn to handle or feed on new flower types (Gegear et al. 2004). This can have extremely detrimental consequences for the health of the colony, by reducing resources brought in from foraging, and thus limiting the size of the colony and number of offspring it can produce. For B. franklini, exotic diseases such as Nosema, which have been introduced through transportation and sale of commercial bumble bee queens and nests (Colla et al. 2006, Otterstatter et al. 2005, Thorp 2003).

Habitat destruction and degradation as a result of agricultural intensification is believed to threaten the future of this species habitat. Agricultural pesticides are also a threat as these can be picked up by bumblebees and, if not immediately deadly to the insects, carried back to their nests to poison other colony members and the brood. However, many efforts are being made to reduce, if not eliminate pesticide application, as the far-reaching repercussions of their use are well-understood.

Currently there are no conservation measures in place to protect B. franklini.

It would be beneficial to attempt to prevent the spread of commercially based disease pathogens to native populations, as these are thought to be having a major negative impact on B. franklini. Further research is needed for:

• the size and range of the remaining population: although very few individuals have been observed, further investigation should be done to reveal precisely how many B. franklini are remaining;
• the species' ecology and biology: a better understanding of the behaviours and general biology of the bee, and its habitat requirements, especially any that might be limiting factors;
• threats: studying the pathology, control, and cross-infectivity of different suspected disease agents of B. franklini, including Nosema bombi, Locustacrus buchneri, and Crithidia bombi (Colla et al. 2006, Otterstatter et al. 2005) would allow for better understanding of the risks to the bumblebee populations and the preventative measures that should be taken. The introduction of these diseases could also be better studies as an element of the risks of commercial trafficking in bumble bees (Thorp 2003);

The habitat of B. franklini needs protection. The protected habitat must have an abundance of suitable pollen and nector aources such as, but not limited to: Lupinus, Eschscholzia, Agastache, Monardella as sources of pollen and nectar for the bees to feed on. Proximity to a natural source of fresh water would also be beneficial as it would increase the flowering season of the plants upon which the bees feed. Also, suitable nest sites are needed, such as abandoned rodent burrows.