Arthropods 5b

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Southern California Arthropods (Mostly) #5: Beetles 2
© W.P. Armstrong 15 April 2009
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Blister Beetle Family (Meloidae)

Soldier blister beetles of the genus (Tegrodera).

Desert blister beetle (Lytta magister).

The inflated blister beetle (Cysteodemus armatus), a curious beetle with a small head and inflated abdomen. Because it superficially resembles a spider it is sometimes called the desert spider beetle. This beetle feeds on ephemeral wildflowers as it scurries across sandy riverbeds and washes. The pitted back has several color variations.

Inflated Blister Beetles In Anza-Borrego Desert
See Desrt Blister Beetle In Anza-Borrego Desert
See An Amazing Bombardier Beetle (Brachinus sp.)


Leaf Beetle Family (Chrysomelidae)

Golden Tortoise Beetle (Metriona bicolor)

This is a stunning, metallic gold beetle slightly smaller than a ladybird beetle. It truly appears like a glistening golden droplet in your garden. The sides of the prothorax and elytra are flared out and extend beyond the body, thus hiding the head and much of the legs. This extended covering is the derivation of the name "tortoise beetle" or "turtle beetle." Although collected in Escondido (San Diego County), the golden tortoise beetle is relatively uncommon in southern California. It is more common in the eastern United States. Both adults and larvae feed on the leaves of morning glories (Convolvulaceae) and related plants. In the case of the aggressive, fast-spreading bindweed (Convolvulus arvensis), this little beetle could actually be beneficial. In order to capture their beautiful golden luster, these beetles should be photographed alive. The color appears especially brilliant during mating season. On dead beetles the golden luster fades rapidly.

Golden tortoise beetle on bindweed leaf (Convolvulus arvensis).

Golden tortoise beetle (Metriona bicolor).

Golden tortoise beetle (Metriona bicolor). Note the outer extension of thorax and elytra.

A deceased golden tortoise beetle (Metriona bicolor).


Click Beetle Family (Elateridae)

Click beetles make a distinctive "clicking sound" when they are placed on their back. They are unable to right themselves with their legs; however, they have a special mechanism on their underside that snaps closed, thus flipping their body right-side-up. The actual mechanism is a pronotal spine that fits into a groove on the mesosternum. The following explanation comes from An Introduction To The Study of Insects by D.J. Borror and D.M. Delong (1964). When placed on its back, it bends its head and prothorax backward, so that only the extemities of the body are touching the surface on which it rests; then, with a sudden jerk and clicking sound, the body is straightened out; this movement snaps the pronotal spine into the mesosternal groove and throws the insect into the air, spinning end over end. Sometimes it takes several attempts (clicks) to land on its legs.

A click beetle attracted to window light in San Diego County.

Western eyed click beetle (Alaus melanops) in Cuyamaca Mts. of San Diego County.


Branch Boring Family (Bostrichidae)

One of the most remarkable and destructive families of beetles includes members of the family Bostrichidae. Adult short circuit beetles (Scobicia declivis) bore into lead sheathing of telephone cables causing short circuiting when moisture enters the small holes. Trunks of native California fan palms in the southwestern U.S. often contain large circular tunnels, the work of huge boring larvae (Dinapate wrightii). The hardwood floor beneath a palm trunk section at the San Diego Museum of Natural History was deeply grooved by one of these larvae. The adult beetle is truly bizarre. In the late 1800's museums paid up to $1,000 to an enterprising collector for one of these striking beetles. The collector (probably a business major) reportedly inflated the value of his merchandise by keeping their exact location a secret.

Stout's hardwood borer (Polycaon stouti). This beetle has very destructive larvae, particularly if you have wood construction in your home made of oak and maple. The larvae of this beetle can even bore into furniture!

The larva and adult of the palm-boring beetle (Dinapate wrightii).

See Palm Wood Bored By Larva Of Dinapate wrighii


Lady Beetle Family (Coccinellidae)

Pupa (left) and larva (right) of 7-spot lady beetle (Coccinella septempuntata).

Larvae of 7-spot lady beetles (Coccinella septempuntata).

Adult 7-spot lady beetles (Coccinella septempuntata). The black pronotum of the convergent lady beetle (Hippodamia convergens) is quite different. It has two long white spots that converge toward each other at the rear of the pronotum.

References:

  1. Borror, D.J. and D.M. DeLong. 1964. An Inroduction To The Study of Insects. Holt, Reinhart and Winston, New York.

  2. Evans, A.V. and J.N. Hogue. 2006. Field Guide to Beetles of California. University of California Press, Berkeley, California.

  3. Evans, A.V. and J.N. Hogue. 2004. Introduction to California Beetles. University of California Press, Berkeley, California.

  4. Hogue, C.L. 1993. Insects of the Los Angeles Basin. Natural History Museum of Los Angeles County.

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