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Chalcosoma caucasus
Range:  Southeast Asia, especially Malaysia
Size:  90 - 120 mm

Chalcosoma caucasus, popularly known as the "Atlas beetle", is one of the largest insects on Earth.   Males often measure up to an impressive 120 mm (4.75 inches) in length.  This particular species is the largest of the genus, which contains two other species, C. atlas and C. mollenkampi.   Like those of most other members of the scarab subfamily Dynastinae, the larvae of Chalcosoma feed primarily on the rich compost which forms within decaying logs and stumps.  Only the males have enormous, curved horns.  The female is far smaller, possesses a fine covering of tiny hairs (called "setae"), and is without horns.

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I have several years of experience rearing these amazing beetles, and have found that they will do quite well in captivity if given proper space and food materials.

Shown here are two males in combat.  The strength of these beetles is very impressive, and males should generally be kept separated in captivity to prevent them from injuring each other.

Photo courtesy of Michael Yeh.

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Chalcosoma caucasus (males) - Image  Michael Yeh

 
Chalcosoma caucasus (pair) - Image  Michael Yeh
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The photo at left perfectly illustrates the extreme physical difference between the sexes in Chalcosoma caucasus.  This is known as "sexual dimorphism", that is, the male and female display marked structural differences in body form and size.  So extreme is this characteristic in some rhinoceros beetle species that in the early days of insect study, the two sexes were actually thought to belong to completely different species.

Photo courtesy of Michael Yeh.

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This photo clearly shows the immense size of a male C. caucasus.  Large scarabs such as this can be safely handled, though they can cut your skin with their very sharp claws if adequately provoked.  Also, care must be taken not to touch a Chalcosoma just behind the pronotal shield, as there is a razor sharp joint there which the insect can suddenly close and give a rather painful pinch.  Beetles this large are extremely strong in relation to their physical size, and one should be a somewhat cautious about placing fingers within range of the mobile horn on the insect's head.
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Chalcosoma caucasus (male) - Image  C. Campbell

 
Chalcosoma caucasus (female) - Image  C. Campbell
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The female C. caucasus.  As can be seen in the second photo on this page, the female of this species is far smaller than the male.  Also, the elytra (wing covers) of the female have a velvety rather than smooth texture.  Females do not enter into contests for mates as do the males of the species, and so she is completely without weapons such as horns.  Like the male though, she can still pinch using the sharp edge where the pronotum meets the elytra.
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A close up photo of the same female pictured above.  Note the finely pitted surface of both the head and pronotal (thoracic) shield.  Some sensory hairs can also be seen just under the area where the antennae (not visible here) are held when not in use.  The female is much more streamlined in form than the male, and her shape is designed for ease of digging and movement within the decomposing logs in which she deposits her eggs.
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Chalcosoma caucasus (female) - Image  C. Campbell

 
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