Conditioning of insects

A recent edit to the wikipedia article on flea circus suggested that fleas can't be trained or conditioned because they have no brain. It also suggested that some fleas are more inclinded to jump and others to walk so it's a case of selection rather than conditioning. This of course contradicts the long running parable of fleas in a jar being conditioned not to jump and once the lid is taken off then the fleas still jump no higher than before the lid was removed.

Firstly to address the question of does a flea have a brain, Richard Fox comments, "The nervous system consists of a dorsal, anterior brain of two or three pairs of ganglia, circumenteric connectives, and a paired ventral nerve cord with segmental ganglia and segmental peripheral nerves.". A bit of explaination of what that means can be found in this article on Brain Evolution which sees a link between the number of sensory organs and brain power.

With regards to the use of those senses and how they affect the behaviour of fleas aspect there has also been some research done, by Michael Dryden aka "Dr Flea".

"Contrast of a moving dark cylinder against a light backdrop was visually attractive to the fleas. No visual orientation was demonstrated under red light. Increasing the complexity of patterns on the target did not increase its attractiveness. Orientation and attraction to a stationary heated target was demonstrated, but required the additional stimulation of air movements to evoke a directed jump. Light, CO2, and air currents stimulated locomotion."

Osbrink, W.L.A. and Rust, M.K., 1985. Cat flea (Siphonaptera: Pulicidae): factors influencing host finding behavior in the laboratory. Ann. Entomol. Soc. Am., 78:29 34.

Walt Noon the magician, inventor and flea circus performer has also reports seeing this behavior.

Apart from the flea circuses there has not been much research into the actual conditioning of fleas how there has been some for other creatures.

Insect Conditioning
http://bjoern.brembs.net/news.php?item.441.3

Conditioning of moths
http://www.nature.com/neuro/journal/v11/n10/abs/nn.2192.html

Pavlov's Cockroach
Classical Conditioning of Salivation in an Insect
Hidehiro Watanabe, Makoto Mizunami*
http://www.plosone.org/article/fetchArticle.action?articleURI=info:doi/10.1371/journal.pone.0000529#n101

So I'm not sure if there is a strong argument for nature vs nurture with fleas. I'd advise anyone hoping to have performing fleas would be advised to tap into the flea's behaviour of responding to heat, light, CO² and air movements.

And finally, some slightly more questionable research into do fleas have higher level emotions.