Review: Diving Beetles of the World

Johns Hopkins University Press is an underrated publisher of natural history titles for both professional scientists and general audiences. Their latest example of impeccable quality is the book Diving Beetles of the World: Systematics and Biology of the Dytiscidae, by Kelly B. Miller and Johannes Bergsten. It is somehow fitting that a relatively ignored family of aquatic beetles gets its "coming out party" delivered by a publisher assumed to be mostly a purveyor of medical books.

Diving Beetles of the World should be a model for a serious and thorough treatment of any entomological subject. Every aspect of the biology, ecology, and classification of the family Dytiscidae is covered here. It is this placement of the beetles in a larger context that is so vital, and so often lacking in other technical publications devoted to various insect taxa. Creating an appreciation for a neglected family of organisms is no small feat, and this publication vastly exceeds expectations.

Rhantus gutticollis from Colorado

It helps greatly that the book is lavishly illustrated with detailed images of perfectly prepared specimens of the beetles themselves. Even a casual student of entomology will feel comfortable at once. Furthermore, keys to the subfamilies, tribes, and genera of diving beetles are likewise illustrated with line drawings and clear, magnified images of critical parts of the beetles' anatomy. Were that not enough, there are also maps showing the global distribution of each genus.

The summary for each genus includes a "diagnosis" of physical characters peculiar to that genus, in case you missed anything during your journey through the keys; a history of classification and relationships to other genera; a description of diversity that includes the number of species currently recognized for that genus; a natural history indicating what habitats and niches the particular genus occupies in nature; and finally a distribution description that complements the maps.

Thermonectus marmoratus from Arizona

The authors, one American and one European, fully recognize the fluid nature of insect taxonomy and have cited virtually every paper and publication written previous to this current work. This sets the stage perfectly for ongoing and future investigations into the Dytiscidae.

Considering that aquatic ecosystems are arguably the most critical habitats on the planet, this book deserves to have an impact far beyond entomology. Every aquatic biologist, environmental consultant, and citizen scientist needs to have this volume in their library, or at least seriously consider it. Should you not make the purchase yourself, please suggest it to your university library.

Colymbetes sculptilis from Massachusetts

Indeed, the only unfortunate aspect of this tome that does not recommend it is the price: $150.00 U.S. Easy for me to enjoy my review copy while my readers are looking at a major expense, no doubt. Still, this is an important work, not just a gift for "the entomologist or naturalist who has everything." How to reconcile quality work with an affordable sale price is a question for another blog, and believe me I am open to suggestions. In the case of Diving Beetles of the World, the product commands the monetary value assigned to it.

Note: Images other than the book cover are my own and are not featured in the book.

The Great Grasshopper Hunt II

I am terribly behind in chronicling field experiences I have participated in this summer, including the second annual(?) "grasshopper hunt" co-sponsored by Mile High Bug Club and the Aiken Audubon Society. Our first one was held last year at Homestead Ranch Regional Park near Peyton, Colorado. This time we opted to head farther south and a little farther east to Chico Basin Ranch; and we were led by grasshopper expert Bill Maynard.

Our intrepid participants © Bell Mead

The ranch is a sprawling 87,000 acres that straddles the El Paso and Pueblo County line. Its wide array of habitats, from sandhills to artificial wetlands, makes for high biodiversity, especially among insects and grasshoppers in particular. In only a few hours our party of roughly ten people observed forty (40) species of grasshoppers, plus many other insects and arachnids.

Pink form of the Broad-banded Grasshopper, Trimerotropis latifasciata

Bill is rather new to the study of grasshoppers, but he quickly masters many aspects of natural history. He is already recognized as a leading authority on birds and dragonflies, with many state and county records to his credit. It is only a matter of time before the same can be said of his expertise in the order Orthoptera to which grasshoppers belong.

Rather than overwhelming you with images here, I will direct you to the Mile High Bug Club Flickr Group where you can peruse the image collection at your leisure.

Snakeweed Grasshopper, Hesperotettix viridis

We would be remiss if we did not also acknowledge the hospitality of the Chico Basin Ranch staff, especially Tess Leach and her family. Her two children were especially curious, and remarkably patient and gentle in their approach to the many grasshoppers we saw.

Three-banded Grasshopper, Hadrotettix triafasciatus (foreground), signaling to a Broad-banded Grasshopper (background) to get out of its territory

The intense heat of that August 6 day sent some members of our party packing by about noon, but who could blame them? The Plains Harvestfly, a type of cicada, made it seem hotter still with its loud, oppressive buzz. All in all, the "expedition" was a resounding success, and no vehicles or people were injured during the odyssey.

Plains Harvestfly, Neotibicen dealbatus

While plains and deserts are prime habitats for grasshoppers, you can find them nearly everywhere. You will be surprised by the number of species you can discover in your own backyard, neighborhood park, vacant lot, or any other patch of wildness. Even now, with the first frosts approaching, grasshoppers are among the few insects left in any abundance. Go take a look for them.

A Beetle Mimicry Complex

This week, on one of my daily walks around our Colorado Springs neighborhood, I encountered a beetle on the sidewalk that gave me reason to pause. I initially dismissed it as a species of soldier beetle that is extremely abundant at this time of year, but something looked a little "off." Sure enough, it was something else; and that got me thinking about mimicry among all these beetles.

Blister beetle, Epicauta stuarti

The beetle on the sidewalk turned out to be a blister beetle, Epicauta stuarti, a species I had not seen before. Blister beetles, family Meloidae, are well known for containing high concentrations of the potent, irritating chemical cantharidin. Blister beetles exude the chemical in liquid form from leg joints and from between other body segments if the insect is squeezed or crushed. The chemical goo can raise painful, scarring blisters on sensitive skin; it can be fatal if ingested.

Ironically, many, if not most, blister beetles don't advertise their toxicity with bright "warning colors." Epicauta stuarti is one that does, but the interesting part is that its pattern of black and orange is very similar to that of our two common autumn soldier beetles. Soldier beetles are in the family Cantharidae, and they also have chemical defenses, which they secrete from abdominal glands. The Colorado Soldier Beetle, Chauliognathus basalis, is common on the plains. Its close relative, C. deceptus, replaces it in the foothills and mountains.

Colorado Soldier Beetle

This kind of shared color pattern that reinforces predator deterrence is called Müllerian mimicry. Both animals can back up their colorful advertisement of toxicity with actual chemical weaponry. This is a very interesting example of mimicry, but it doesn't end here. Other local beetles have jumped on the bandwagon.

End Band Net-wing Beetle, Calopteron terminale

Also appearing at this time of year is the End Band Net-wing beetle, Calopteron terminale. They generally occur in far fewer numbers than the soldier beetles, but can be mistaken for them with just a passing glance. It is widely assumed that net-winged beetles (family Lycidae) are distasteful to predators, because they have colorful patterns in many cases. Whether this has been proven I do not know.

Net-winged beetles may exaggerate the effect of their wardrobe by raising and lowering their wing covers (elytra) in a unique display. As adults, they feed on nectar, and the "honeydew" secreted by aphids and related insects as a sweet liquid waste product. Larvae of netwing beetles feed on fungi or metabolic products of fungi. Whether this diet can be converted into toxic compounds is debatable.

Longhorned beetle, Crossidius discoideus

While the jury may still be out on whether net-winged beetles are indeed toxic, there is no question that yet another mimic in this complex is pulling one over on predators. The longhorned beetle Crossidius discoideus fools us into thinking it is dangerous to eat by mimicking the pattern of the solider beetles. It can even be found on the same flowers as the soldier beetles and is difficult to easily separate from them, except for its long antennae. This brand of mimicry is called Batesian Mimicry, whereby a harmless animal masquerades as a dangerous one.

Crossidius discoideus has no common English name. As a larva, it bores in the root crowns of Broom Snakeweed, Gutierrezia sarothrae, or Jimmyweed (Isocoma spp.). The adults feed on flower pollen and nectar. Broom Snakeweed is also where the blister beetles hang out, so I may have to look more thoroughly for them now.

Longhorned beetle, Batyle suturalis

Yet another kind of longhorned beetle, Batyle suturalis, appears just before the populations of soldier beetles explode. Is it, too, taking advantage of a similar color pattern to gain "cover" from predators? What I would like to know is which of the truly toxic beetles started this whole complex. The blister beetle? The solider beetles? We will likely never know, and that is part of the appeal of entomology. It is an endlessly curious endeavor, seeking the answers to more puzzles than mankind will ever unravel.

Do Insects Feel Pain? A Revealing Question

At some point in their career, every entomologist will be asked the question "do insects feel pain?" A surprising amount of research has gone into answering that question or, in some instances, unrelated research has provided insight into that query. My answer to that question has more to do with the person asking it, and as far as I know, that is a unique response.

Questioning the capacity for insects to feel pain says more about the one who intends to inflict it.

As one who interacts with the public more than many entomologists, it has become evident that while some people have no qualms about ending the life of an insect, even advocating extremely inhumane techniques ("Kill it with fire!" is a common reply to someone else's social media request to identify a household insect), there is an increasing tolerance for insects, even in the home. If the creature is unwelcome, there is now often a plea for a non-lethal means of dealing with the uninvited arthropod.

The flipside of this more empathetic response to "bugs" is the question of whether insects feel pain. The obvious, hoped-for answer is "no, they don't." The person asking is then relieved of guilt for harming or killing any insect in the past, present, and future. So, while the new trend is for more people, especially women, to seek humane methods of insect control, many people still look for examples of how insects do not deserve empathy and compassion as a way to vindicate their own behavior towards other organisms.

The bottom line in the question of whether insects feel pain is thus the unspoken question of whether killing insects and spiders falls into the category of cruelty to animals. Legally, it would be difficult to argue that insects, being animals, are exempt from that crime. Obviously, this is not the case, and I do not see that implied public consensus changing anytime soon. Swatting a mosquito could be an act of "self-defense," though, considering the atrocious diseases that those biting flies can transmit.

Ok, so you want a scientific answer? Most entomologists I know resort to the short answer that insects do not have "pain receptors" like higher animals. This means they have no nerve cells devoted to the perception of pain. Insects can sense heat and cold, for example, and various chemical and tactile stimuli, but not pain as we would define it.

Is the wasp feeling no pain while being killed by the spider?

The fact that many insects, and other arthropods, willingly sacrifice limbs and other body parts in order to survive predator attacks is a testament to how apparently immune to pain they can be. A missing leg hardly slows down a grasshopper. Tattered wings rarely encumber a butterfly finishing its mission of mating and procreation.

As a colleague and fellow blogger noted in his own treatment of this question, another important aspect of physical pain is the emotional distress that comes with it. Ascribing human emotions to non-human organisms is known in the scientific community as "anthropomorphism," and is considered a big no-no when attempting to conduct unbiased research and observations. So ingrained is the concept of avoiding anthropomorphism that we now have to question whether the unemotional conclusions we draw in animal behavior studies are really the correct ones. The truth probably lies somewhere in the middle.

The fact that people are asking questions like this that leave open the possibility that insects and other arthropods are sentient beings is a hopeful sign, regardless if that belief is based in reality. We could certainly stand a little more empathy for other living things. Then again, look how we treat other members of our own species.

Source: Ballenger, Joe, 2016. "Do insects feel pain?," Ask an Entomologist.