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Beetles

Black Blister Beetles Consuming Asters

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Blister beetles are so-called because they contain a chemical in their hemolymph, or blood, called cantharidin.  If rubbed or pressed the beetles release cantharidin as a defense mechanism, which causes blistering on human skin.  The Black Blister Beetle (Epicauta pennsylvanica) belongs to a genus of beetles that are highly toxic to horses — a few beetles fed in a single feeding of alfalfa can be lethal.

As larvae, most blister beetles are predators, often invading wild bee colonies and consuming bee larvae, as well as nectar and pollen.  Black Blister Beetle larvae and other blister beetles in the genus Epicauta prey on the eggs of grasshoppers.  Female Black Blister Beetles lay clusters of eggs in the soil in late summer. The small, active larvae that hatch from these eggs crawl over the soil surface entering cracks in search of grasshopper egg pods which are deposited in the ground. After finding an egg mass, the blister beetle larvae become immobile and spend the rest of their developmental time as legless grubs. The following summer they transform into the pupal stage and soon emerge in the adult stage. This is why blister beetle numbers increase dramatically following high grasshopper populations.

Once they mature into adulthood, Black Blister Beetles feed on plants (phytophagus) and are commonly found on flowers, especially those in the Aster/Composite family. They are said to be there for the nectar and pollen, but the Black Blister Beetle pictured denuded several aster blossoms of all petals during the time it was observed.

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The Emerald Euphoria Beetle: A Distinctive Scarab

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Beetles comprise almost 40% of described insects and 25% of all known animal life-forms. There are about 30,000 beetles known as scarabs or scarab beetles in the family Scarabaeidae. They make up about 10% of all known beetles. You may be very familiar with scarab beetles without even being aware that that is what they are – they are as close as the nearest Japanese Beetle or June Bug (beetle).

Scarabs are generally oval-shaped and stout. The smallest are about .08 inches and the largest (Hercules beetles) can reach 6.7 inches. Most scarabs are black or brown, but many, especially tropical species, have bright colors and intricate patterns. They have distinctive, clubbed antennae composed of plates called lamellae that can be compressed into a ball or fanned out like leaves to sense odors (see photo). Their diet is extremely varied and includes plant material, fungi, fruit, carrion, insects and even the slime left by snails.

One fruit- and flower-eating species is the Emerald Euphoria beetle, Euphoria fulgida (pictured). It is usually bright green or bluish. Emerald Euphoria beetles belong to the subfamily Cetoniiae, the flower or fruit chafers. One of its most distinctive characteristics is its ability to fly (using its second pair of wings) while its first pair (the hardened, colorful elytra) remain closed — most beetles open and extend their elytra during flight.

Unlike most scarabs, Emerald Euphorias are diurnal, making it possible to see this species visiting flowers in order to consume nectar, pollen and petals.  (Thanks to Richard Wyatt for photo op.)

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Blister Beetles Mating

5-9-18 blister beetles mating_U1A1519Blister beetles derive their name from the fact that they secrete a yellow blood-like substance called hemolymph which contains the blistering compound cantharidin. Severe burns and even poisoning can occur if the quantity encountered is large enough. (Baled hay containing the carcasses of blister beetles can be lethal to livestock that eat it.)

Defense isn’t cantharidin’s only function, however. Cantharidin is secreted by the male blister beetle and given to the female as a copulatory gift during mating. Afterwards, the female beetle covers her eggs with it as a defense against predators.

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Ladybugs Maturing & Seeking Shelter

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Ladybugs, along with roughly 88% of all insects, pass through four separate stages (egg, larva, pupa, adult) in their life cycle. This form of maturation is referred to as complete metamorphosis. Like many other insects that experience complete metamorphosis, the larval, pupal and adult stages do not closely resemble one another. While most of us would have no trouble recognizing an adult ladybug, the two middle stages are strikingly different from the adult spotted beetle we’re familiar with. After a ladybug egg hatches, the larva emerges, looking a bit like a tiny alligator. Anywhere from seven to twenty-one days later and after several molts, the larva attaches itself to a leaf and pupates. The pupa assumes yet another bizarre form, which some feel resembles a shrimp. Within a week or two the pupa matures and transforms into an adult ladybug. Most species of ladybugs hibernate (technically enter “diapause,” as it’s referred to with insects) as adults in large groups under leaf litter, logs and other protected spots.


Locust Borers Laying Eggs

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The Locust Borer (Megacyllene robiniae) is so-called because its host tree is Black Locust (Robinia pseudoacacia). Locust Borer larvae tunnel into a tree’s trunk and branches, weakening the tree and making it susceptible to wind breakage. In addition, these tunnels serve as a primary infection site for the wind-borne spores of the fungus Phellinus robiniae, which causes a damaging heart rot disease in Robinia species. If you see a Black Locust with many dead and broken limbs, and/or knotty swellings on the trunk, chances are great that it has been attacked by Locust Borers.

The conspicuous, brightly-colored adults appear when goldenrod is in bloom. Adults are commonly seen feeding on goldenrod pollen. Mating takes place now, in the fall, and eggs are laid  in cracks, wounds and under loose bark of a Black Locust tree. The eggs hatch in about a week, the larvae bore into the inner bark of the tree and each larva makes a small hibernation cell and overwinters there. In the spring the larvae begin to bore into the woody part of the tree, enlarging their tunnels as they grow. By mid-summer they pupate and adult beetles emerge in late summer. Previously confined to the native range of Black Locust in the Northeast, Locust Borers have spread with the trees throughout the U.S. and parts of Canada.

 


Golden Tortoise Beetle Larvae Feeding

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When it comes to ingenuity, the Golden Tortoise Beetle (Charidotella sexpunctata) larva has all others beat! Instead of discarding its feces, it collects them and uses them as a means of chemical protection. Golden Tortoise Beetle larvae have a “fecal fork” on their last abdominal segment which they hold over their body. They also possess a muscular, telescopic anus which they can manipulate in such a manner as to deposit their feces onto their fecal fork. Bits of shed exoskeleton combined with days of feces accumulate on this fork and create an effective fecal shield. Golden Tortoise Beetle feces contain alkaloids from the plants that they’ve eaten (Bindweed and other plants in the family Convolvulaceae) and consequently the shield wards off predators. (Photo:  Golden Tortoise Beetle larva with fecal shield; inset – adult Golden Tortoise Beetle)

 


Leaf Beetles

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There is a group of 1,500-plus beetles in North America known as “leaf beetles.” They all have an expanded and two-lobed/heart-shaped section of their leg just above the claws. These lobes bear specially modified hairs which help these plant-eating beetles walk on plant stems and smooth leaves. The majority of leaf beetles are specialists, feeding only on a single species of plant or groups of closely related plants. Many leaf beetles are considered pests, including the Colorado Potato Beetle, Spotted Cucumber Beetle, Striped Cucumber Beetle, Spotted Asparagus Beetle and Northern Corn Rootworm Beetle.

 One of the most striking leaf beetles, and one that is not a “pest” is the Dogbane Beetle (Chrysochus auratus), so called because its diet is restricted to the leaves of Dogbane (Apocynum androsaemifolium). Its distinctive iridescent green, copper, green and blue body is hard to miss. (Photo: Dogbane beetle on Dogbane)