When Varroa Mites Hitch a Ride

Bug Squad    By Kathy Keatley Garvey   March 1, 2016

Varroa mite on a honey bee (drone) pupa. (Photo by Kathy Keatley Garvey)Those blood-sucking varroa mites (Varroa destructor) are considered the No. 1 enemy of beekeepers. In powerful numbers and weakened colonies, they can overwhelm and collapse a hive.

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:

  1.  Are the nutrients of the substitute host close enough to those of honey bees to support immature mite development? 
  2. 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? 
  3. 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 destructorreproduction.

Sounds like a good research project!

A varroa mite attached to a honey bee forager. It's the reddish brown spot near the wing. The bee is foraging on lavender. Photo: Kathy Keatley Garvey http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=20360

Bumble Bees and Spiders Don't Mix?

Bug Squad - Happenings in the Insect World   By Kathy Keatley Garvey

Bumble bees and spiders don't mix, you say?

Well, they will at the Bohart Museum of Entomology's open house from 1 to 4 p.m., Saturday, July 26. The family-centered event, free and open to the public, takes place in Room 1124 of the Academic Surge building on Crocker Lane, UC Davis campus.

Actually the theme is about spiders: "Arachnids: Awesome or Awful?" There you'll see black widow spiders, jumping spiders, cellar spiders and the like. But you don't have to "like" them as...


Karate Kick!

Bug Squad - Happenings in the Insect World   By Kathy Keatley Garvey    July 7, 2014

If you've ever watched a karate competition, you've probably seen the roundhouse kick, tornado kick, the reverse roundhouse kick or the flying side kick.

But have you ever seen a bee do that?

We were photographing sunflower bees on our Mexican sunflowers (Tithonia) yesterday, trying to catch the territorial dive-bombing. We were shooting with a Canon E0S 7D equipped with a 100mm macro lens. Settings: ISO, 1600. Shutter speed,  1/1400 of a second. F-stop, 10.

If bees could engage in humanlike conversation, imagine this dialogue:

"This flower is mine! Get off! I want my ladies to have that flower!"

"No, it's not! It's mine. I was here first! Leave me alone!"

For awhile, a large bee, a male longhorned bee, Svastra obliqua (as identified by native pollinator specialist Robbin Thorp, emeritus professor of entomology at UC Davis), appeared to be the "king of the mountain." It held its ground...er...floral resource.

Suddenly, faster than my shutter speed, a smaller bee of a different species, a male longhorned bee, Melissodes (probably Melissodes agilis, Thorp said) headbutted Svastra,  a scene reminiscent of a World Cup play.

One swift kick by Mr. Svastra and a surprised Mr. Melissodes shot straight up in the air, whirling end over end. 

Roundhouse kick? Tornado kick? Reverse roundhouse kicK? Flying side kick?

Whatever it was, the "bee master" won.

And he wasn't even wearing a black belt.

Read and view more images:  http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=14544

Visit the Kathy Keatley Garvey Bug Squad blog at: http://ucanr.org/blogs/bugsquad/

Learn About Native Bees and the Flowers They Visit

Bug Squad - Happenings in the Insect World   By Kathy Keatley Garvey

It's just in time for National Pollinator Week, June 16-22. 

Native bee enthusiast Celeste Ets-Hokin of the Bay Area is on a three-fold mission: She wants to protect North America's premier pollinators; she wants to inspire an appreciation for the importance and diversity of our native bees; and she wants people to create a habitat for native bees in their own gardens.

So, as an educational tool meant for all ages, Ets-Hokin originated the idea of a Wild Bee Gardens app to "show the dazzling diversity of North America's native bees." The app links native bees to many of the flowers they frequent.

The app is a comprehensive introduction to what the UC Berkeley zoology graduate calls "the essential world of native bees." It's comprised of some 300 photographs of native bees and their floral resources (primarily by entomologist/insect photographer Rollin Coville of the Bay Area) plus 100 pages "of extensive background and educational material in the form of guides."

Topics covered in the guides include:

  1. The role of native bees in our natural ecosystems
  2. The ecology and life cycles of native bees
  3. How to create a successful bee garden
  4. How to identify the native bee visitors that will appear in these gardens

Ets-Hokin wrote the text, seeking scientific consultation from native pollinator specialist Robbin Thorp, emeritus professor of entomology at the University of California, Davis (co-author of the newly published Bumble Bees of North America: An Identification Guide) and UC Berkeley faculty member Gordon Frankie. She also praised the "amazing job" of the design and development team, Arlo and Rebecca Armstrong. 

Where to get Wild Bee Gardens? The I-Pad version  is now available on the Apple App Store for the introductory price of $3.99. Those purchasing the app will receive the upcoming, expanded iPhone version at no additional cost, said Ets-Hokin, adding that they also will receive free downloads of all future enhancements.

Ets-Hokin devotes her time to the public awareness and conservation of native bees. This includes establishing a native bee demonstration garden with the Alameda County Master Gardeners at Lake Merritt, Oakland; and coordinating the publication of native bee calendars



 Visit the Kathy Keatley Garvey Bug Squad blog at: http://ucanr.org/blogs/bugsquad/