- 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
So, what's a meloid beetle to do?
Here you are, a meloid beetle foraging on a Mexican sunflower (Tithonia) and these long-horned digger bees keep dive-bombing you and pestering you.
Then a Gulf Fritilllary butterfly (Agraulis vanillae) decides it wants a share of your flower.
So, it's take to take flight!
Blister beetles (family Meloidae) are known throughout the insect world for their defensive secretion of a blistering agent, cantharidin, according to Wikipedia. "About 7,500 species are known worldwide. Many are conspicuous and some are aposematically colored, announcing their toxicity to would-be predators."
Don't touch a blister beetle because that poisonous chemical can blister your skin.
Did you know that cantharidin is the principal irritant in Spanish fly, a folk medicine prepared from dried beetles in the Meloidae family? Wikipedia tells us so.
The UC Statewide Integrated Pest Management Program (UC IPM) offers information about blister beetles in a UC Pest Management Guideline on its website. "Blister beetles are narrow and elongate and the covering over the wings is soft and flexible. They may be solid colored (black or gray) or striped (usually orange or yellow and black) and are among the largest beetles likely to be found in a sweep net sample in alfalfa."
UC IPM points out that cantharidin is toxic to livestock. "Cantharidin is contained in the hemolymph (blood) of the beetles and may 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. As the name implies, handling these insects may result in blisters, similar to a burn, on the hands or fingers. Blister beetles have been a serious problem in alfalfa in the northern United States, the Midwest, and the south for many years, but until recently have not been a problem in California."
Blister beetles have been linked to the death of several dairy cows in the southern Owens Valley, according to UC IPM. "At this point, it is not known if blister beetles are widespread or confined to the Owens Valley. Likewise, it is not known if the problem is likely to spread and hence become a common occurrence in California alfalfa. In the meantime, growers and PCAs (Pest Control Advisors) are advised to be on the lookout for blister beetles and to contact their farm advisor for advice if these insects are found."
