- Author: Kathy Keatley Garvey
If you're feeling overwhelmed during the holiday season and just can't seem to concentrate, check out the focus and intensity of this male territorial bee, a Melissodes agilis.
It was back in July of 2015 when I spotted a meloid beetle on a Mexican sunflower, Tithonia rotundifola, in a Vacaville pollinator garden.
The Melissodes did, too.
Now the meloid beetle is a blister beetle (family Meloidae). Don't touch these beetles because they emit a poisonous chemical, cantharidin, that can blister your skin. It makes for great defense. Touch me, and I'll blister your skin. No wonder the chemical is used to remove warts.
Blister beetles are also known to infest alfalfa hay, and are toxic--even deadly--to livestock. See "Blister Beetles" published by the Montana Agricultural Experiment Station.
"Cantharidin, a vesicant produced by beetles in the order Coleoptera, has a long history in both folk and traditional medicine...Historically, cantharidin has been used as an aphrodisiac, an abortifacient, and a veterinary medicine diuretic." --Cantharidin Revisited, JAMA Dermatology.
So here's this bee targeting the beetle. Oh, the intensity of those eyes...much like a last-minute shopper eyeing a 50 percent-off gift, the last in stock, and ignoring the attempts of last-minute shoppers to grab it.
Did the beetle move?
Not a bit. It rose and ate some of the pollen that the bee was trying to save for its own species.
- Author: Kathy Keatley Garvey
And well you should: honey bees are the global workhorses of the pollination community and pollinate about one-third of the food we eat, including fruits and vegetables and some nuts, primarily almonds (California's almond acreage exceeds 1.6 million.)
But to continue the alliteration--butterflies, bats, birds and beetles are pollinators, too.
That includes "the good guys and gals," the lady beetles, aka ladybugs, which devour aphids.
However, this is National Pollinator Week and a good time to reiterate that insects can be both pollinators and pests. Take the blister beetles (family Meloidae, which contains about 2500 species) are one color or striped. Blister beetles are a pest of alfalfa and many species secrete a poisonous chemical called cantharidin, which protects them from their predators but is quite toxic to livestock, especially horses.
According to the Alfalfa Pest Management Guidelines published by the UC Statewide Integrated Pest Management Program (UC IPM): “Blister beetles do not cause widespread feeding damage to alfalfa; however, they contain a chemical, cantharidin, which is toxic to livestock. Cantharidin is contained in the hemolymph (blood) of the beetles, and can contaminate forage directly, when beetles killed during harvest are incorporated into baled hay, or indirectly, by transfer of the hemolymph from crushed beetles onto forage. Horses are particularly susceptible to the toxic effects of cantharidin. Consuming as few as six beetles can kill a horse.”
A 2020 news story out of the Midwest related that beetle-infested hay purchased at an auction in South Dakota led to the deaths of 16 horses at a riding stable in Mauston, Wisconsin. Reporter Carleen Wild wrote that even a small amount of the bug itself or cantharidin "can be toxic enough to kill a horse within 72 hours." The horse owners reported what looked like "blisters and holes down their esophagus and throughout their insides."
The odorless, colorless chemical also blisters the human skin; physicians use it to remove warts.
That's one powerful chemical.
