all these pictures present the Al Ain city in United Arab Emirates & Burimi city in Oman


Monday, 27 October 2008

Dragonfly and it's eyes

All insects have two large compound eyes on the sides of their heads, and three simple lens eyes or ocelli in the centre. There are two small lateral ocelli and a larger middle one called the median ocellus. In the dragonfly, the median ocellus is curved.

“Ocelli are generally thought to have poor resolution,” says Josh van Kleef, a PhD student at RSBS who is leading the research on dragonfly vision. “The general belief has been that they’re there to measure general light levels which can be used to stabilise their flight. The idea is that if they detect that light levels are falling they’re heading down, and if the levels are rising they’re heading up. This information is then used to guide their movement.”However, Mr van Kleef’s research is revealing that a dragonfly’s middle eye does a lot more than simply pick up on general light levels.

“The median ocellus is a simple lens containing about 1500 photoreceptors,” he explains. “These photoreceptors are connected to 11 large neurons (nerve cells) which go from the retina all the way down the neck of the dragonfly to the insect’s motor centres. It’s a very direct route from a visual response to a change in movement, and allows for a very rapid response to their environment.
Reefrences: , Bob Riemer for giving me the link.

1 comment:

arie said...

its good information for student