That would be the varroa mite, Varroa destructor, an eight-legged external parasite that attacks and feeds on honey bees. Those mites can spread viruses and decimate a healthy colony.
How can you monitor, mitigate and manage them?
Extension apiculturist Elina Lastro Niño and her lab are hosting a short course on "Varroa Mite Management Strategies" from 9 a.m. to 4 p.m., Sunday, Oct. 13 at the Harry H. Laidlaw Jr. Honey Bee Research Facility on Bee Biology Road, University of California, Davis.
"Current beekeeping challenges call for all beekeepers to have a solid understanding of varroa mite biology and management approaches," said Niño, in describing the course. "We will dive deeper into understanding varroa biology and will devote majority of the time to discussing pros and cons of various means to monitor, mitigate, and manage this crucial honey bee pest."
The course, limited to 20 participants, will cover varroa biology, treatment options and chemical-free options. Participants are to bring their bee veil or suit. The $200 registration fee covers the cost of course materials, lunch and refreshments. The last day to register is Monday, Oct. 7. Click here to register.
Originating in Asia, the varroa mite is now found throughout most of the world. It arrived in Japan and the Soviet Union in the early 1960s and South America in the 1970s. From the 1970s to 1980s, it spread to South America, Poland, France, Switzerland, Spain, and Portugal. The pest was first detected in the United States in 1987, in Canada in 1989, and in 1992 in the United Kingdom. It has since spread to Ireland, New Zealand and Hawaii, but to date, has not been found in Australia.
The female is reddish brown, while the male is white. They measure 1–1.8 mm long and 1.5–2 mm wide.
The course is sponsored by the UC Davis-based California Master Beekeeper Program, (CAMBP). directed by Niño. The program uses science-based information to educate stewards and ambassadors for honey bees and beekeeping. For more information, contact CAMBP program manager Wendy Mather at firstname.lastname@example.org.
We remember seeing a varroa mite attached to a foraging honey bee one warm summer day in our pollinator garden. The mite was feeding off the bee and the bee was feeding on the nectar of a lavender blossom.
Didn't seem fair.
We've never seen a varroa mite on bumble bees or carpenter bees, but Davis photographer Allan Jones has--and he's photographed them. (See below)
When varroa mites tumble off a honey bee and into a blossom, they can hitch a ride on other insects, such as bumble bees and carpenter bees.
"Varroa have been recorded hitching rides on bumble bees and yellowjackets," observed native pollinator specialist Robbin Thorp, distinguished emeritus professor of entomology at UC Davis. "Varroa have been reported as feeding on larvae of these and other critters--but not successfully reproducing on them. Also bumble bees and yellowjackets typically overwinter as hibernating queens not as perennial colonies like honey bees. Thus they are not suitable hosts for Varroa."
Extension apiculturist emeritus Eric Mussen says that bees other than honey bees aren't reproductive hosts for the varroa mite.
"As far as I know, Varroa destructor may be able to find soft areas of the exoskeleton of insects other than honey bees and feed on them," he says. "I have no idea whether or not the substitute hemolymph would sustain the mites for very long. The mites have practically no digestive capabilities. They simply utilize the previously-synthesized bee blood, to which they seem to be perfectly adapted."
"Since the mites reproduce on honey bee pupae, there are a number of considerations about potential other reproductive hosts," Mussen said, citing:
- Are the nutrients of the substitute host close enough to those of honey bees to support immature mite development?
- Can immature mites that develop properly at honey bee cell environmental conditions (temperature and relative humidity) find a similar environment in the nests of other insects?
- Do other insects tolerate the presence of mites on their bodies or in their brood nests?
Like honey bees, bumble bees do segregate their pupae in single cells, Mussen says, but he was unable to find any studies devoted to whether bumble bee pupal conditions support Varroa destructor reproduction.
Sounds like a good research project!
Newly published research by a Michigan State University-led team indicates that one of the reasons why the varroa mite is so destructive is because it infiltrates hives by smelling like a bee.
The parasitic mite, or Varroa destructor, is a "blood sucker" that feeds on bees. Scientists and beekeepers alike consider it the world's No. 1 enemy of honey bees.
MSU entomologist Zachary Huang, a lead author of the paper in Biology Letters, and his fellow researchers showed that "mites are able to change their surface chemicals to an entirely different species of honeybees," according to an article in the American Bee Journal. "Further, they also revealed that the mites were able to make these changes rather quickly - adapting in days rather than evolving over generations."
The varroa mite was initially found in Asian honey bees (Apis cerana) and then shifted hosts to the European honey bee (Apis mellifera). It was first detected in the United States in 1987. Today it is found in hives throughout the world except in Australia.
The eight-legged reddish-brown parasite, about 1–1.8 mm long and 1.5–2 mm wide, is a blood sucker that's difficult to control, according to Extension apiculturist emeritus Eric Mussen of the UC Davis Department of Entomology and Nematology. Mites transmit viruses (there are now some 22 named RNA viruses) that can wipe out a hive. A familiar mite-transmitted disease that beekeepers see is DWV or Deformed Wing Virus. Mites can also lower the protein level of a bee's blood, and reduce its weight and life span.
Mussen says that mites spread from colony to colony by phoresy (animal-to-animal transport). They ride on flying drones (males) and adult worker bees (females). They also spread changing hosts on flowers.
"A mite enters a honey bee cell just before or during the time it is being capped," Mussen points out. "It feeds on older larva or prepupa. Sixty hours later, the mite lays its first egg. The egg will hatch in about 24 hours."
"The number and release of offspring depend on the length of the pupal stage. The queen is pupa for 8.5 days (no mites). The worker is pupa for 12.5 days (1.3 mites) and the drone is pupa for 14.7 days (3 or 4 mites)," he says. Thus, due to the longer time required for drone development, drone pupae get the worst of it.
"When maturing, the newly emerged mites climb onto adult bees and feed by puncturing the intersegmental membranes and sucking the bee blood," Mussen related recently to a UC Davis class. "Often these are nurse bees that stay around the brood nest. Sometimes the hosts are drones and older foragers that are flying from the hive every day. Eventually the new mite climbs off the nurse bee onto a comb in the brood nest and enters a cell. The reproductive cycle starts and within 6 days, 44 percent of the young mites have moved into the brood cells; within 12 days, 69 percent of the mites are in the brood cells; and within 24 days, 90 percent of the mite are in the brood cells."
"If there is no brood, the mite has to feed on adult bee blood every six days or so to remain alive," Mussen says. "Mite life expectancy in summer is around 60 days; bees about 42 days. Mite life expectancy in the winter is up to 9 months; bees about six months."
Now if scientists could only figure out how to eliminate the varroa mite from the world's hives...
To a beekeeper, it's a four-letter word.
Specifically, the varroa mite, also known as Varroa destructor.
It's a small (think flea-sized) crab-shaped parasite that feeds on bees, either in the brood (immature bees) or on adult bees.
Extension apiculturist Eric Mussen, member of the UC Davis Department of Entomology faculty, just updated his Bee Brief on this blood sucker. His Bee Briefs, all posted online on the department Web site, can be downloaded for free.
This Bee Brief is titled "Treating Colonies for Varroa Mite Infestations." (You'll also want to read his updated colony collapse disorder (CCD) Bee Brief.)
It's apparent, Mussen says, that resistant mites are now prevalent in the United States, including California.
"Chemical testing has demonstrated that varroa mites commonly are resistant to fluvalinate, coumaphos and amitraz. Losses of wintering colonies were over twice as high as 'normal' during the early 2000s, with one of the worst losses (40 to 60 percent) of California (and total U.S.) commercial colonies over the 2005-05 winter. Infested colonies dwindled away during the fall and winter."
Meanwhile, a hive without a varroa mite is a scarcity indeed.
You can see varroa mites on the larva (below) and on an adult bee.
Just think if you had a blood sucker on you like that.