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Order of the Month
Highlighted Coleoptera
by John Jackman
Tiger Beetles, Cicindela spp. [Cicindelidae]
Tiger beetles are long legged fast running predators that feed on other
insects. They are also very good fliers. These beetles are very alert and
can detect you when you approach. When you get to close they will fly off
a short distance and sit down again until you approach once more. After
they fly forward several times they will sometimes fly all the way back to
their original location suggesting that they have a territory that they
patrol.
Larvae tunnel quite deeply into the ground. The larvae sit at the surface with their head closing the flat opening of the tunnel. They will move quickly out to capture prey that runs by. The larvae have hooks on the end of the abdomen which are used to hold them in the tunnel if a predator attempts to pull them from the tunnel.
Tiger beetles are favorites with some collectors who collect nothing else. The bright colors, considerable variation and challenge of capturing them contribute to the popularity of this group for collectors.
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June Beetles, Phyllophaga spp. [Scarabaeidae]
June beetles are most often seen at lights at night. The name June
beetle is a bit misleading in Texas because some species emerge as early
as February. The genus Phyllophaga is a large one with about 150 species
in Texas. There are several other genera of related scarab beetles like
Diplotaxis, Polyphylla and Anomala that can mistaken for these beetles.
Larvae of June beetles are called white grubs and they spend their life in the soil. Most feed on roots of plants and some species are pests of lawns and gardens.
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Convergent Ladybird Beetle, Hippodamia convergens Guérin-Méneville [Coccinellidae]
The
convergent ladybird beetle is one of the most common and readily
recognized beetle in Texas. The name convergent comes from the two white
lines that converge on the pronotum.
Ladybird beetle larvae look very different than the adult beetles. These grubs are elongate and flattened with projections on each segment. However, like the adults they feed on aphids and other small insects so they are beneficial because they contribute to the balance of nature.
Ladybird beetles come in many sizes and colors. Some of the smaller species in the genus Scymnus are not easily recognized as ladybird beetles.
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Ironclad Beetle, Zopherus nodulosus haldemani Horn [Tenebrionidae]
The
ironclad beetle is one of the slowest moving insects you can find.
They are very well camouflaged when they sit on the bark of a tree. When
disturbed these beetles often fall to the ground and play like they are
dead. They are very long lived as adults with at least one specimen that
was known to remain live in captivity over seven years.
Adult ironclad beetles are extremely hard and very difficult to crush. They are also difficult to put a pin through them to make a museum specimen. Other species in this genus occur in Mexico and central America where they are sometimes used as living jewelry. Beetles are adorned with cut stones and then tethered to a button with gold chains.
Larvae of this species feed on the roots or trunk of oaks and possibly other trees.
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Caterpillar Hunter, Calosoma scrutator (Fabricius) [Carabidae]
The
caterpillar hunter like many ground beetles is a predator on other
insects. These beetles have bright green elytra, with blue on the legs and
black on the underside. They are long-legged and fast running. They
sometimes come to lights especially in the spring.
Caterpillar hunters can spray a caustic substance somewhat like the bombardier beetles. The substance can bother the eyes of a predator and burn the skin for a few hours. Sometimes when the beetles are very abundant they become a problem around lighted areas and cause a consider nuisance and odor problem.
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Whirlygig Beetles, Dinuetes spp. & Gyrinus spp. [Gyrinidae]
Whirlygig beetles swim on the surface of lakes and rivers. They
sometimes congregate in large numbers even into the thousands. The adult
beetles are streamlined and have the legs modified to swim. Each compound
eye is divided into two sections: one section can see above the water line
and the other section sees below the water line at the same time.
Some of the whirlygig beetles produce a noticeable odor. The odor is similar to apple cider or fermented apples. The odor is apparently a defense against predators like fish.
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Green June Beetle, Cotinis nitida (Linnaeus) [Scarabaeidae]
The
green June beetle is one of the more conspicuous scarab beetles in
Texas. The bright metallic green and large size make them very visible.
The adults are good fliers. The sometimes accumulate on flowers or
over-ripe fruit. The adults can sometimes be trapped with fruit bait.
Larvae of this species are typical “white grubs” and are found in the soil where they feed on roots of plants. The larvae have a very peculiar behavior when they sometimes crawl along the surface of the ground on their backs.
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Eastern Hercules Beetle, Dynastes tityrus (Linnaeus) [Scarabaeidae]
The
eastern Hercules beetle is one of the largest beetles in Texas. This
scarab has light green elytra with irregular spots. The pronotum has a
long horn on the males while females have almost no horn at all. Many of
the scarab beetles have longer horns in the males. Some species even have
males with various lengths of horns.
The eastern Hercules beetle never seems to be very common but they are sometimes found under lights. Larvae are huge grubs that feed in organic matter. They are sometimes dug up in compost heaps or old decaying logs.
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Eyed Click Beetle, Alaus oculatus (Linnaeus) [Elateridae]
The
eyed click beetle is one of the largest of the Elateridae in
Texas. They can be about and inch and a half long as adults. They have two
distinct eye spots on the pronotum which gives them the name and they are
generally grey in color. The larvae are elongate, cylindrical, brown, and
somewhat hardened. They feed on dead wood such as tree stumps. Adults are
often found under lights.
Larvae of click beetles are known as wireworms. Some species feed on roots of crops and can damage pototoes, sweetpotatoes, and various other crops. The family has many species most of which are brown in color. Some species are only about a quarter of an inch long.
Click beetles get their name from a curious behavior that they exhibit. When click beetles are flipped on their back they tense the body and snap the pronotum backwards rapidly often producing an audible click. The motion can propel the beetle into the air often several inches high. Usually the beetle lands on its feet and it can start running away after it “clicks”.
One genus of click beetles which occurs most commonly in South Texas is Pyrophorus. This genus has two eye spots on the pronotum which can produce light much like the fireflies. These eye spots can be seen from several hundred feet away which creates a bit of an eerie feeling. Bioluminescence is rather uncommon in insect groups.
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Fireflies, Photuris and Photinus [Lampyridae]
Fireflies
are well known because they flash lights at night. The
lights are used in the courtship ritual allowing the females and males to
locate each other for mating. Each flash that we see is really a series of
flashes that occur so fast that we can not distinguish them as individual
flashes. The flash pattern is species dependent and allows the species to
locate the proper mate. Depending on the species both males and females
will flash.
Larvae of fireflies are predators feeding on snails and other types of food. They have not been reared in captivity and relatively little is known about the immature stages. In some species the females stay in a grub-like form even as adults. Some immatures can also emit light and are known as “glowworms”. The name glowworm is also applied to another beetle family Phengodidae.
Many people believe that there has been a reduction of the number of fireflies. However, there has not been a long term survey of the populations to know if this is true or not. Usually the perceived reduction in firefly numbers is based on childhood memories of fireflies while someone grew up in the country where fireflies are likely to be more abundant and noticeable. Several other factors are also blamed for firefly number reduction like: habitat destruction, fire ants, pesticide use, etc. However, there is little convincing evidence that these factors influence the population levels of fireflies.
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Sawtoothed Grain Beetle, Oryzaephilus surinamensis (Linnaeus) [Cucujidae]
Sawtoothed grain beetles feed on milled or damaged grain. They
sometimes enter homes when they are brought in with food products like
cornmeal, flour, cereal, or pasta. They sometimes feed on other food
products as well. Both adults and larvae feed on the same type of food and
the numbers can build up when food products are stored for long times.
The adults are about an eight of an inch long and brown. The general body shape is elongate with the pronotum edges serrate (toothed) hence the name sawtoothed. The larvae are grubs with brown heads and cream-colored bodies.
There are many other types of beetles like confused flour beetle, larder beetle, and some weevils that can share the same habitat.
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Yellow Mealworm, Tenebrio molitor Linnaeus [Tenebrionidae]
The
yellow mealworm is the common mealworm sold as pet food and fish
bait. They feed on milled grain products like corn meal, oat meal, or
chicken feed. They are relatively slow growing but can be reared in
culture on wheat bran, rolled oats or other grain products.
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Black Blister Beetle, Epicauta pennyslvanica (DeGeer) [Meloidae]
The
black blister beetle is common on goldenrod in the fall of the
year. Blister beetles sometimes occur in clusters and feed on alfalfa and
other legumes. Blister beetles can release a substance called cantharidin
which can blister the skin which is where they get their name. Adults are
sometimes attracted to lights and can be found there also.
The larvae of blister beetles feed on grasshopper eggs, brood of ground nesting bees and other soil inhabiting insects.
The striped blister beetles are a problem in alfalfa production. Hay can be infested with blister beetles can be contaminated with the dead beetles. Horses that ingest only a few dead beetles can die from a reaction to the cantharidin.
Cantharidin is sometimes called Spanish fly and is sold as an aphrodisiac. Actually, it is an irritant in the urinary tract and is quite dangerous.
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Huisache Girdler, Oncideres pustulata LeConte [Cerambycidae]
The large brown beetle (twig
girdler) has a mottled appearance on the body and long
antennae like most Cerambycidae. They feed on mimosa, huisache and
sometimes mesquite. The adult females chew around a branch making a notch
all the way around. The damage reduces the flow of water to the outer part
of the plant and eventually kills the branch completely. The female lays
eggs in the outer branch where the grubs will develop. The damage by the
female will essential create dead wood that the grubs need to develop.
Damaged branches can be up to three inches or more in diameter.
The damaged limbs often fall off in the winter especially after a high wind. The damaged limbs can be held indoors where the beetles will emerge.
There are several other types of beetles that girdle limbs. A related but smaller species prefers pecans and other hickories.
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Twelve Spotted Cucumber Beetle, Diabrotica undecimpunctata howardi
Barber [Chrysomelidae]
The
twelve spotted cucumber beetle has several other common names like
southern corn rootworm and spotted cucumber beetle. The adult beetles are
very common along roadsides on various flowers and in gardens. The adult
beetles have been suspected as carrying a disease between cucumbers and
other cucurbits. The larvae are grubs in the soil that feed on roots.
Often the damage goes unnoticed but they can be a problem in vegetable
gardens and sometimes on corn.
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Boll Weevil, Anthonomus grandis Boheman [Curculionidae]
Boll weevils are perhaps the worst pest of cotton across the southern
US. The adult weevils lay eggs in the cotton squares (flower buds) and the
grubs feed on the developing buds. Sometimes they attach the bolls which
are the fruit after the plant has bloomed. Adult weevils feed on the
foliage, fruit or flowers. Pollen is important for the adult weevils to
produce eggs.
Across the south there has been a wide area program of boll weevil eradication which now extends into areas of the Texas. Most of the areas east of Texas are now considered free of boll weevils. Once the weevil is gone the management of pests in cotton production becomes much easier.