A Case of Mistaken Identity: Is it a Bug, or a Beetle?
In the back of my mind, I recalled a recent gardening article that I'd read about the slow progression of an invasive species, the red lily beetle (Lilioceris lilii, across North America. Appropriately dubbed "The Red Menace," these bright red beetles are terribly destructive, and can entirely defoliate and kill a lily or frittilaria plant in a single season. You may also hear them described as the red lily leaf beetle, or the scarlet lily beetle. I pulled out my smart phone and searched for an image, hoping that my hunch was incorrect. My mother has beautiful Oriental and Asiatic lilies on the other side of the yard, and I hated the thought of those thousands of beetles covering them and stripping them of leaves and buds!
It was difficult to determine at a glance if the pictures I found matched the mass of insects, so my mother got her camera and took several close-up pictures. She also collected a few of the bugs, with the promise that she'd take them to the director of Extension Services.
He was able to quickly allay our fears and assure us that the bright red insects she collected and photographed were not the red lily beetle. We were surprised by his positive identification of them, however. It turns out they were the nymph stage of a very familiar bug, the box elder bug (eastern: Boisea trivittatus or western: Boisea rubrolineatus). He said he could immediately tell they were not a beetle, based on the mouthparts and wings.
His identification led me to do some further investigation into how, exactly, to identify whether an unknown insect is a beetle (Coleoptera) or a bug (Hemiptera). I always thought the terms "insect" and "bug" were interchangeable, but it turns out that "bugs" are a particular type of insect, distinctly different from beetles.
First, true insects have a few features in common. All true insects have three body parts: the head, abdomen, and thorax. They also have six legs and a hard exoskeleton, rather than an interior skeleton. They also both have one or more sets of wings, and a hard wing cover that folds over the wings to protect them.
It is the differences that allow for positive identification, however. There are several fairly simple ways to distinguish between bugs and beetles, even for a relative novice like myself.
Beetles have pincer-style mouth parts called mandibles, designed for tearing and biting plant materials or other insects. Red lily beetles, such as the specimen on the left, put these tearing, chewing mouthparts to work on our precious lilies, leaving destruction in their wake. Other beetles may be predatory or cannibalistic, and use the mandibles to attack and dismember their prey.
Bugs, on the other hand, have a probiscus-type mouth, designed for piercing and sucking juices from plants, or blood from animals. I'm sure you are familiar with the habits of mosquitoes, for example. Box elder bugs fall into this category, as they have mouths designed for feeding on the seed pods of female box elder trees. They are hard to see, however, as they are usually folded up against their underbelly, between their legs. The mouthparts are barely discernible in this close-up of a box elder bug, for example.
Another simple way to identify whether your sample is a bug or a beetle is to examine the hard wing covers. In a beetle, the wing covers will meet to form a single straight line down the center of the back. One source recommended thinking of the characteristic ridge down the center of the hood on a Volkswagon Beetle as a reminder. Beneath these hard, rigid wing covers are one or more sets of elytra, or secondary wings capable of flight.
In a bug, the wings will overlap and form diagonal lines, something like a V or X. Beneath these protective sheaths, bugs also have secondary flight wings. In the box elder bug, right, the wing covers have a distinctive red and orange pattern. I never would have guessed that the wingless nymphs we saw were related to this easily recognizable bug!
One final way to distinguish between bugs and beetles may be more difficult to identify, unless you happen to see them emerging from their eggs. Beetles have a larvae or pupae stage, which may look like a grub or worm. In red lily beetles, this stage is particularly disgusting, as the yellowish larvae hang out on the buds and beneath the lily leaves, and coat themselves in their own excrement to discourage predators. One of the methods of manual control of the beetles is to crush them in this larval stage, if you can stand the black slime!
Bugs, on the other hand, emerge as nymphs, or immature versions of their adult self. The box elder bugs we found were in this early stage, before their hard wing covers had emerged. I grew up with box elder bugs, but never would have guessed that the bright red rounded insects we found would morph into the familiar, flat-backed bugs with their distinctive red and black patterned wing covers.
Our story did have a happy ending. Our first response to the huge mass of red insects was to look up how to control the invasion with chemical treatments. If it were a few isolated specimens, they would be easy enough to drop into a bucket of soapy water, or manually squish (though the very idea gives me the willies.) Apparently, red lily beetles are very difficult to catch as adults, as they drop to the ground and lie with their black belly up, blending in to the ground or mulch below, at the first sign of movement in their direction. Some experts recommend draping white sheets below an infected plant before attempting to manually remove the lily beetles, to increase your chances of finding and destroying them before they can breed and lay eggs. Because of this defensive habit, they are much easier to control at the poop-encrusted larval stage. We were facing insurmountable odds, however, with the sheer numbers that were crawling all over the western side of her house. If they truly were the invasive red lily beetle, chemical controls would have been the only viable option when dealing with those numbers.
Happily, however, we did our detective work first, and learned there was no threat whatsoever. While box elder bugs may be a nuisance when they seek shelter inside warm houses in the autumn, they pose no danger to either plants or people. They are very specialized feeders, seeking out primarily the seed pods of female only box elder trees. They may occasionally also feed on maple and ash trees, but don't do any significant or lasting damage. Their mouth parts are very specific to their food source, and they couldn't bite a human if they tried!
The mass of brilliant red bugs soon grew wings and disappeared. Though my mother tried to locate a more mature specimen to provide follow-up pictures for this article, the entire population seems to have packed up and moved away. I'll be curious to find out if they re-appear when the weather turns chilly, or if they've permanently relocated!
Photographs from Flickr Creative Commons and Wikimedia Commons have been used in accordance with their respective usage policies. Pictures are listed in the order they appear in the article.
The thumbnail image at the start of the article was taken by my mother, Edythe Hill, of one of the clusters several days after we first discovered them. All rights reserved. Do not copy or redistribute.
Red lily beetle (mandibles): Flickr Creative Commons, some rights reserved, by mikeyp2000.
Box elder bug (probiscus): Flickr Creative Commons, some rights reserved, by e_monk.
Red lily beetle (wing covers): Flickr Creative Commons, some rights reserved, by mikeyp2000.
Box elder bug (wing covers): Wikimedia Commons, public domain.
Red lily beetle larvae: Flickr Creative Commons, some rights reserved, by pirhan.
Box elder bug nymphs: Flickr Creative Commons, some rights reserved, by benet2006.
My thanks go out to the photographers who make their work available for use! I appreciate their contributions to this article!