‘Ground beetles’, a spectacular insect group, featured at MVFN natural history talk
Report of October 2012 MVFN Lecture
by Joel Byrne
About 350,000 species of beetles occupy this planet. They are found in nearly every terrestrial habitat and many watery ones, pole to pole. There are more named species of beetles than there are named species of any other group. When I saw the title of Dr. Henri Goulet’s presentation to the Mississippi Valley Field Naturalists: My Favourite Insect Group – Ground Beetles (Carabidae), I thought of a quote attributed to J.B.S. Haldane, a distinguished British biologist, who, when asked what he had learned about the ‘creator’ from looking at nature, replied that the creator “. . . has an inordinate fondness for beetles,” referring to the enormous abundance of beetle species. Henri Goulet, MVFN’s second speaker, in the lecture series Nature Beneath Our Feet, is a research scientist emeritus with Agriculture and Agri-Food Canada, and he also has a fondness for beetles—ground beetles. Why, out of 160 families of beetles would he choose to study ground beetles? The answer was found in his talk, as he shared some of his fond memories in a lifetime of adventures tracking down his favourite group of animals.
Henri (he is a friend) opened his talk by posing some basic questions: what is a beetle, what is a ground beetle? A series of photos outstanding for their clarity, detail, and colour followed, displaying anatomical features of beetles that distinguish them from other insect Orders. One could clearly see that the beetles have no tail-like structure and that their wing covers do not overlap. It is these wing covers or elytra which give rise to the name of the Order of insects to which beetles belong, i.e. Coleoptera, meaning ‘sheath wings’ in Greek. In this Order is a suborder, Adephaga, meaning ‘voracious.’ And in this voracious group is the ground beetle family, Carabidae, our speaker’s favourite.
Carabid beetles number some 1700 species strong in North America; 250 species around Ottawa. The carabids have long antennae, large jaws, and long legs. Some are very fast, among the fastest animals in the world, for their size. Combine their murderous mandibles with their long speedy legs and you have a formidable predator. Even their larvae are usually big-jawed, active insect predators. All this is bad for their prey, often invertebrates, and good for us since a lot of invertebrates we consider farm and garden pests, aphids, slugs and caterpillars, are consumed. If any invertebrate wishes to avoid being devoured by a ground beetle in Canada, they should retire to a cave, since this is one of the few habitats ground beetles don’t inhabit, we learned.
Then came the big question, posed by Henri—Why do I find ground beetles fascinating? Henri’s fascination and fondness for ground beetles goes back to his childhood days in winters when he dug down in snow, then into and under the leaves where he found many of his pals stiff with cold, and warmed them up. But what got Henri interested initially in studying ground beetles was seeing species with dark metallic reflections.
There are many other reasons ground beetles became so fascinating to Henri. Unlike butterflies and dragonflies which quickly fly away, adult ground beetles are easy to pick up under debris or under the soil surface. The adults are quite easily seen, ranging in size from 1.5 mm to 30 mm, most being 5-10 mm in size. Adults live at least one season and of course, can be found even under snow. Adults come in a great variety of shapes. Many shiny black ground beetles have a ‘typical’ shape, athletic, but some are anything but typical. The ‘snail eater’ is a case in point having ‘strikingly elongated mouth parts’ the better to lunch on the inside of a snail’s shell. There are round sand beetles that look like pills. Bombardier beetles are much wider aft than most, perhaps to house a sort of two-chambered gun at the end of their abdomen where they mix hot chemical ‘bullets’ and ‘fire’ them with an audible pop at anything that threatens them. Many in the Adephaga suborder are ‘accomplished stinkers’, thus avoiding predation.
Henri then showed us phenomenal photos of what, I believe, fascinated us all the most— their great variety of colours. The wing-cover slides alone, entitled Elytral Sculpture, were worth the price of admission. “Our perception is very much affected by what we are.” We are humans and most of us are more interested in butterflies than a lot of black beetles because as humans we are attracted to colours. So when the first slide of elytral sculpture popped onto the screen there was a collective sigh. Mind-bogglingly beautiful metallic greens, bronzes, purples and blue blacks, more emerald greens. Also turquoise wing covers trimmed with copper called ‘the best’ in Canada, Carabus vietinghoffi, from the land of small willows. It was as if a sculptor and a jewelry designer had collaborated in crafting them.
As if an expert sculptor and jeweler had collaborated to craft it! A Carabus vietinghoffi, from the ‘land of small willows,’ with its turquoise wing covers trimmed with copper. This is the ground beetle Henri considered ‘the best’ in Canada. Photo Henri Goulet.
There followed a series of photos of completely-assembled, i.e. entire specimens of ground beetles, starting with solely black species, then switching to beetles ranging from pale to dark single-coloured, to two-coloured species, and then three-coloured species. Then came the ones with dark metallic reflections, the ones that initially interested Henri, then ones with bright metallic reflections (my favourites), and then species with two and three hues of metallic reflections, and finally species with metallic hue and pigment colours. At which point Henri said, “So I hope I’ve exposed you to a lot of colours.” We were mesmerized, colour-saturated!
This ground beetle, Elaphrus clairvillei, inhabits only marshy meadows and swampy places. Dr. Goulet is an excellent photographer and here, as in many photographs, he has captured the stunning beauty of the beetle. Photo courtesy Henri Goulet.
The balance of the talk was devoted to many other special features of ground beetles which could have been a talk in itself. Most ground beetles hide in the day. Look for them under logs and rocks, and in stumps. Ground beetles are found on all land habitats except in water (one species stays under rocks submerged by tides). Most species are potentially excellent bio-indicators because their habitat requirement varies from quite narrow to extremely narrow. For example Elaphrus clairvillei inhabits marshy meadows and swampy places, but will not live in bogs as they are too acidic. Some adult ground beetles are very long-lived, 2-7 years. Most ground beetles are finicky about where they live but not fussy about what they eat. A good example, ‘caterpillar hunters’ (Calasoma sycophanta), are forest ground beetles which emerge in the spring, look around for their prey and venture out and stay out if their prey is present, otherwise they return to the ground. Among ground beetles there are predators, scavengers, and herbivores (many are ‘weed-seed’ eaters), and even parasites (the very colourful leaf beetle parasites for example)—a very wide range of modes of life indeed.
A huge fan of the ‘ground’ beetles, Dr. Henri Goulet (centre), fields questions after his talk at the Almonte United Church, while others examine some of the many species specimens provided by the speaker for display. Photo Pauline Donaldson
The talk wound down with a lively question and answer period, while in the background the slide show continued. There was an initial burst of oohs! and ahs! as very colourful beetles seemed to dash across the screen: fabulous close-ups of live tiger beetles on the hunt. What a spectacular way to end the show!
A word about Henri Goulet’s photographs— superb! His photos, taken with meticulous care, will long be remembered by those who set aside a few hours of a fall evening to learn and be entertained by the learning. What I came away with was the impression of incredible beauty in the colours and design of the host of ground beetles, each species with its own variation on the general plan.
I enjoyed the lecture so much I saw it twice!
Resources: reference books on ground beetles are Common Ground Beetles (1987) by Trevor G. Forsyth and An Illustrated Identification Guide to Adults and Larvae of Northeastern North America Ground Beetles (2010) by Yves Bousquet.
