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Insect Antennae

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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Scarab Beetle Antennae

6-16-14  scarab beetle antennae 261Beetles in the family Scarabaeidae share several characteristics, including specialized antennae. The last three to seven segments of each antenna form flat plates, or lamellae, that can be expanded like a fan (see Japanese Beetle insert) or folded together into a club (see June Beetle photo). When these plates are separated they are being used as sensory devices to detect odors. When folded together, the antennae are used as clubs by some species of fighting male scarabs. The next time you see a June Beetle, Rose Chafer or Japanese Beetle, take a second to inspect its antennae before parting company.

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Clean Antennae Necessary for Sensory Perception

8-9-13 conehead katydid cleaning antenna 098Insect antennae are among the most sensitive and selective chemical-sensing organs in the animal kingdom. They detect information crucial to an insect’s survival, including odors, sounds, humidity, changes in water vapor concentration and air speed. Antennae are capable of these feats because of the sensory receptors covering them which bind to free-floating molecules. Experiments with cockroaches, ants and flies confirm that insects engage in antennal grooming — removing foreign materials from the surface of their antennae with their mandibles — primarily to maintain acute olfactory reception. Pheromones, chemical signals that are vital to insect communication, are used to convey alarm, attract a mate, mark territory and lay out trails, among other things, and clean antennae enhance these messages. (Photo is of a Sword-bearing Conehead Katydid cleaning its antenna.)

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