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Friday, Oct. 18, 2002


Stag beetle

* Japanese name: Miyamakuwagata
* Scientific name: Lucanus maculifemoratus
* Description: This is a large, reddish-black, heavily armed (and armored) beetle. Males have a fearsome but elegant pair of antlerlike jaws, about 15 mm long, with sharp teeth. Body length ranges from 43-72 mm. Females do not have such huge jaws, and their bodies are smaller, about 32-39 mm. Despite their relatively mild appearance compared to the males, however, female stag beetles can give quite a nip. The male's jaws are too large to close hard.
* Where to find them: From Hokkaido to Kyushu, from July to August, in woodlands and forests, especially in mountains where oak trees grow. Miyamakuwagata are different from other Japanese stag beetles; they don't lay eggs in rotten trees. Eggs are laid in layers of dead leaves and wood at the base of dead trees, where the leaves are half-transformed into soil. Here, they hatch into larvae, and then crawl into the dead tree, where they can grow, protected.
* Food: The larvae feed on the dead wood and decomposing leaves into which they hatch. Adults feed on the sap leaking from wounds in trees.
* Special features: Male stag beetles have a wide range of lengths, with size variations of up to 30 mm, but the size variations in females are all within 6 or 7 mm. Size distribution in males is clustered toward each end, meaning that most male beetles tend to be either small or big, but not in between. Why? The reason is that for adult males, there are two ways of going about fulfilling their genetic role and copulating with a female: They can fight another male, or they can skulk around, try to get past a big male and copulate with his female. In other words, there are two tactics for getting females. It is best to be big if the male is going to fight his opponent (the fights take place on the trunks of trees, males wrestling each other with their jaws, attempting to flick the opponent off the trunk). For the female there is only one way to be successful (be big with lots of eggs), and so females don't vary in size as much as males do.

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