Giant beetle limit

2007/08/13 Rementeria Argote, Nagore - Elhuyar Zientziaren Komunikazioa

• Teknologia
• Biologia
• Eboluzioa
• Zoologia

The largest species of beetle in the world is the Titanus giganteus of the Amazon rainforest, with an average male size of 13.5 cm and almost 17 cm (not counting antennas). They are galantas, but there was a time when the beetles were much older, in the late Paleozoic. How did those giant insects disappear? To answer this question, researchers at the Argonne laboratory investigate where the size limit of insects is and what it depends on.

Through x-rays, they observe the interior of four species of beetle of very different sizes. And they have seen that the larger ones have a higher proportion of tracheal tubes than the smaller ones, which are structures that use to transport oxygen to all parts of the body. According to these researchers, the size of the beetles is mainly limited by the tracheal tubes of the legs, and according to the calculations made, the largest size that the beetle can have is that of the Titanus giganteus.

So how did the beetles live bigger than them? For the explanation is in the oxygen of the air: In the late Paleozoic, the air had more oxygen than now, making it easier to expand into the beetle body.

Photo: Argonne National Laboratory