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Anita’s Blog – Big, Scarce, Not Rare

Big-eared Blister Beetle. (Photo by Anita Westervelt)

I do like a good polka dot even if it’s on a bug – and who doesn’t love a Lady beetle, right? But this was no Lady beetle. It was a big bug, sitting at the top of the moth sheet like it was waiting for me to take its portrait. So, I did.

Big-eared blister beetle, Cissites auriculata, (Family Meloidae), identified via It was 1 ½ inches long. I discovered it prior to the first hint of sunrise. It hung around after I’d doused the black lights and the sun rose. I captured more angles.

After initially identifying the beetle, I’d read a bit about the big-eared blister beetle and learned that it is new to Texas: “Its first U.S. record in Texas was in Brewster County, at Big Bend National Park, in 1988,” according to website at this link: is one of my go-to sites for insect information. I can generally count on it for larval host information. Such was the case with big-eared blister beetle. Amazingly, the larval host is not a plant.

The larvae, like most meloid beetles, are parasitic on bees.

The genus Cissites attacks carpenter bees (Xylocopa spp., Hymenoptera: Apidae) (references in Quinn 2011). Texas Entomologist Mike Quinn, currently Curatorial Associate at The University of Texas Insect Collection, UT, Austin, compiled a comprehensive data sheet at this link: The species is uncommon, the site notes; the beetle can be attracted to lights.

The big ears are explained: “Males have a curiously shaped head with bulging temples above the eyes (the “big ears”) and long, stout black mandibles. Females have a smaller head and shorter, stout mandibles,” according to information at the Virginia Tech Insect Collection website. explains that the auriculata, in the species name, means eared, which refers to the protruding temples. This site describes the big bug’s range as being in west and south Texas and south to Panama during January to June in Texas. “Adults are aphagous, (they) lack the ability to feed.”

Other than the iNaturalist observation of May 1988, the only other observations of this beetle in the United States are from the Rio Grande Valley; there are less than 35 uploaded observations. A San Juan (Hidalgo County) mention in January 2009, was documented on The observation map on iNaturalist picks the bug up along the Texas and Mexico border beginning in 2017, in Hidalgo and Cameron counties, showing it only as far north as Laguna Vista in 2019, with the majority of sightings after 2020 (speculatively due to citizen science participation in the annual City Nature Challenges).

There are approximately 100 species of blister beetles in Texas, according to Texas A&M AgriLife Extension information.

If you’re one of those who likes to pick up and study insects and critters in the field, think twice about doing that with blister beetles, if you haven’t already deduced that silent caution from its name.

Adult blister beetles, no matter the species, produce a chemical named cantharidin. It is released when the bug is squashed. For instance, you might think to smack one like a mosquito if one were walking across your arm or foot. But don’t. Flick it instead. The oil in the chemical can cause blisters or welts on exposed skin, according to a Terminix website. The blisters and welts may linger for about a week.

The good news is that blisters won’t form just by a bug landing or walking on you, apparently. I didn’t know that when I was photographing the Big Bug.

I had looked behind the moth sheet and found I was standing amongst a small field of striped blister beetles that seemed to be hugging blades of St. Augustine grass. I took a photo and then carefully stepped away. I probably should think about wearing closed-toed shoes to check out what has been attracted to the lights in the dark.

Red-margined Blister Beetles. (Photo by Anita Westervelt)

Although I assumed these striped blister beetles were common, they are not. And they aren’t striped.

Red-margined Blister Beetles. (Photo by Anita Westervelt)

Red-margined blister beetle, Pyrota tenuicostati, identified via iNaturalist, another not so common species of Texas blister beetles. Their range is mostly Central Texas to Costa Rica, usually found from May to July, according to An iNaturalist map shows them as far north in Texas as Waco.

I described them as black and red striped. A close look at a photograph of them depicts the elytra, the wing casing, covering each wing as black with red margins.

Had I researched red-margined blister beetles prior to photographing in the dark, I would have come across a startling account that may have prepared me for finding a minor congregation of them in the grass.

Interestingly, it could have been worse. A compilation by Mike Quinn, reflects on a 2005 account by Lee Elliot and Bill Carr, during a field excursion in Goliad County, Texas: “Then we looked up and saw literally clouds of these beetles flying through the air and aggregating on trees in the area. I would say that there were 10,000 or more individuals in an area of a couple of acres.”

The site also reported that adult, red-margined blister beetles emerge in late May and June and feed on leaves but are especially attracted to flowers where they feed on nectar and pollen. They gather in groups, so large numbers can occur in concentrated clusters in a field.

I can attest to a group larger than what I was comfortable with in the grass behind my moth sheet and exploring the tripod and clamp springs of the shop light fixture holding the black light bulbs.

Red-margined Blister Beetles on light clamp spring. (Photo by Anita Westervelt)

There are a few cautions about blister beetles of special interest to horse owners because of the defense mechanism of the beetle. It can also be highly toxic if (accidentally) ingested, for people and also especially for horses and poultry. “For this reason, horse owners are particularly sensitive to blister beetles in hay.” A good Texas A&M AgriLife Extension website to visit is at this link:

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