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Dynastes neptunus
Range:  northwestern South America
Size:  55 - 160 mm

Dynastes neptunus is rather similar in form to the somewhat larger D. hercules, but its body is black instead of brown.  Also, the horns are more slender and often much more curving than in D. hercules, and the cephalic horn is of similar length to the thoracic one.  Additionally, there are two lesser yet very pronounced horizontal horns parallel to the base of the thoracic horn.  D. neptunus had a reputation as being a very rare beetle for many years, but that was before it was discovered that it mainly only emerges from hiding just before dawn, and perhaps that is why it was not frequently seen previously.  It is now known to be quite common in the rain forests throughout much of the northwestern portion of South America.

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A pair of D. neptunus.  The female in this photo is very large, nearly matching the male in body size.  The female's antennae can be clearly seen.  Scarabs have a specialized, highly sensitive type of antenna called a lamelliform antenna.  It consists of a series of flattened plates upon which the sensory cells for smell are located.  Normally held together in club-like fashion, they can be spread out like a fan when in use.

Image courtesy of NAOKAWA.

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Dynastes neptunus (pair) - Image  NAOKAWA

 
Dynastes neptunus (male) - Image  Fan Lin
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Make note of the extremely long cephalic horn, which is of approximately the same length as the thoracic horn.  This is characteristic only of D. neptunus, although the cephalic horn of D. satanas, also from South America, can also be quite long.

Photo courtesy of Fan Lin.

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Notice that the entire dorsal surface of the female is heavily pitted, giving it a very granular texture.  Like the females of other rhinoceros beetle species, her body is streamlined for easy of digging through decaying wood.  She also has a very stout and strong clypeus (the anterior section of the head) which she uses as a wedge for pushing through decayed wood.

Photo courtesy of Fan Lin.

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Dynastes neptunus (female) - Image  Fan Lin

 
D. neptunus with D. hercules - Image  Fan Lin
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A D. neptunus (top) shown alongside a D. hercules (bottom) for comparison.  Males of D. neptunus are very often just as large as those of D. hercules, though the latter have a greater bulk on average.

Photo courtesy of Fan Lin.

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