An online resource based on the award-winning nature guide


A Gardener’s Favorite Beetle

bronze carabid 161Ground beetles (family Carabidae) are fast moving beetles, many of which are predators with specialized diets.  One ground beetle (Cychrus caraboides) eats only snails (its head and thorax are very slender, allowing access to the inside of a snail’s shell).  Another, Harpalus rufipes, limits its diet to strawberry seeds.  Loricera pilicornis uses bristles on its antennae to trap springtails and mites.

The Bronze Carabid, Carabus nemoralis, (pictured) uses its large curved mandibles to crush and slice through prey – it will eat or try to eat just about any invertebrate, but specializes in capturing and eating slugs. Its hardened forewings, or elytra, have a coppery sheen to them, and parts of its thorax and the edges of its elytra are iridescent purple. This nocturnal, introduced, flightless, one-inch-long beetle resides throughout the Northeast and is already actively pursuing slugs.

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Dung Beetle Feeding on Bear Scat

10-16 dung beetle 127Wherever there is scat, or dung, there are dung beetles. This is a photograph of a dung beetle in heaven as it has located a black bear’s gigantic (apple-filled) scat, which will provide it with food for a long, long time. Some species of dung beetles (rollers) shape pieces into balls and roll them away and bury them to eat later or lay their eggs on. Some species (tunnelers) bury their dung by tunneling underneath the pile of scat. And a third group (dwellers) actually lives inside dung piles.

Most dung beetles prefer the scat of herbivores. There are always bits of food that do not get digested, and these bits are what a dung beetle feeds on. Dung beetle larvae eat the solids, while adult beetles drink the liquids contained in the scat. A given species of dung beetle typically prefers the dung of a certain species or group of animals, and does not touch the dung of any other species.

Dung beetles have a brain that is the size of a grain of rice, yet they are very sophisticated insects. They use celestial clues (the Milky Way) in order to roll balls of dung in a straight line. Dung beetles are known for “dancing,” which helps them orient themselves after their path has been disrupted. They use their dung balls to regulate their temperature, and cool off. (In very warm climates, around noon, when the sun is at its peak, dung beetles will routinely climb atop their dung balls to give their feet a break from the hot ground. Thermal imaging has shown that dung balls are measurably cooler than the surrounding environment, probably because of their moisture content.) And dung beetles keep track of the number of steps they take and the direction from which they came (instead of landmarks) in order to return to their nest with a ball of dung.

Even though they are remarkably clever, dung beetles can be duped! A flowering plant native to South Africa (Ceratocaryum argenteum) produces large, round nuts that are strikingly similar in appearance, smell, and chemical composition to antelope droppings, which the dung beetles accordingly roll away and bury, effectively sowing a new generation of C. argenteum.

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Blister Beetles’ Defense Mechanism

10-5 short-winged blister beetle 064Blister beetles are aptly named, for when they are disturbed they emit a yellow, oily, defensive secretion (cantharidin) from their joints which usually causes blisters when it comes in contact with skin. This toxin deters many potential predators and is especially effective against ants. According to naturalist/forester/writer Ginny Barlow, as little as 100 milligrams is reported to be fatal to humans if ingested, and this amount can be extracted from just a few beetles. Humans used to crush and dry blister beetles and use the resulting concoction for gout and arthritis. It was also used as a popular aphrodisiac known as Spanish fly. Because of its toxicity, it is no longer widely used in medicine.

Cantharidin is, however, indirectly used by tree-nesting nuthatches. With a limited number of tree cavities, there is competition among animals using them to raise their young, especially between squirrels and nuthatches. Nuthatches have been seen with Short-winged Blister Beetles (Meloe angusticollis, see photo) in their beaks, “sweeping” them on the bark around tree cavity entrances. The nuthatches don’t eat the beetles, they strictly use them as tools. It is assumed that the birds do this in order to repel squirrels with the cantharidin that is smeared on the tree. (Thanks to Ginny Barlow for photo opportunity.)

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Rose Chafers Busy Eating & Being Eaten

6-26-15  crab spider with rose chafer 020All of a sudden we are besieged by Rose Chafers, those tan beetles that feed on roses and peonies, as well as the foliage of many trees, shrubs and other plants. The reason for their sudden appearance has to do with their life cycle.

Adult Rose Chafers emerge from the ground in late May and early June. (Because the Rose Chafer prefers sandy soil to lay eggs, plants located on sandy sites are most likely to be attacked.) Adult beetles feed on plants for three or four weeks, generally until late June when they mate, lay eggs in the soil and then die shortly afterwards. Two to three weeks later, the eggs hatch into small, white grub‑like larvae which feed on the roots of grasses and weeds. The larvae spend the winter in the soil below the frost line before pupating and emerging as adults in the spring.

Rose Chafers contain a toxin that can be deadly to birds, but apparently not to crab spiders, at least the one that was photographed drinking the innards of a Rose Chafer it had caught. As testimony to their drive to reproduce, a Rose Chafer, minutes after this picture was taken, mounted and attempted to mate with the Rose Chafer that was being consumed by the crab spider.

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Coyotes Feeding on Deer Carcasses

12-22-14 deer carcass 394Ninety percent of a coyote’s diet is animal matter, including creatures as varied as meadow voles, mice, muskrats, raccoons, beetles and grasshoppers — basically, anything it can outrun. Coyotes have the reputation as major predators of deer. While research confirms that deer (and rabbits) comprise a good portion of a coyote’s diet in the Northeast, the majority of the deer that coyotes consume is scavenged as carrion (see photo). Because they cannot move as fast as adult deer, fawns are more vulnerable to coyote predation.

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Predaceous Diving Beetles Remaining Active

10-9-14   p. diving beetle 143While meadows and fields are experiencing a sharp decline in insect life at this time of year, one habitat where insects remain active in the fall and often through the winter is ponds. Among the year-round active pond invertebrates are Predaceous Diving Beetles, which can still be observed as they row through the water, intermittently surfacing to thrust their abdomen above the water line in order to procure a bubble of air from which they breathe. Their middle and hind legs are fringed with long hairs, making them efficient at rowing through the water in search of prey or detritus to eat.

Predaceous Diving Beetles lay their eggs on and in plants above the waterline in early spring. When the eggs hatch, the larvae drop into the water. Mature larvae crawl out of the water to pupate in damp chambers on the shoreline. They emerge as adults and re-enter the water, where they remain active through the winter, under the ice. (Water Scavenger Beetles look a lot like Predaceous Diving Beetles, but they stroke first with one leg, then another, not simultaneously like Predaceous Diving Beetles, and they come to the surface of water head first to secure air.)

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Tortoise Beetle Larvae Making Fecal Shields

8-1-14  tortoise beetle larva with fecal shield 049Instead of discarding feces, or frass, some insects save their waste matter for defensive purposes such as “fecal shields.” These are coverings over the back of the larvae that are made largely of feces and provide either physical or chemical barriers to predation. Adult Tortoise Beetles have a type of shield (hence, their name), but it is formed from expanded, hardened forewings, and is not a fecal shield. The larvae of these beetles have fecal shields which serve as chemical deterrents, preventing most predators from even touching them. The deterrent in the feces comes from the beetles’ food source — plants in the order Solanales. Tortoise Beetle larvae have what is known as a “fecal fork” on their last abdominal segment, which they hold over their body. The larvae maneuvers its muscular, telescopic anus, or “anal turret” in such a manner as to excrete its feces and bits of shed exoskeleton onto the fecal fork, forming an umbrella-like fecal shield.

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