Optics of the ultraviolet reflecting scales of a jumping spider.
The jumping spider Cosmophasis umbratica from Singapore is strongly sexually dimorphic. The males, but not the females, reflect ultraviolet as well as green-orange light. The scales responsible for this are composed of a chitin-air-chitin sandwich in which the chitin layers are three-quarters of a wavelength thick and the air gap a quarter wavelength (where lambda=600 nm, the peak wavelength of the principal reflection maximum). It is shown that this configuration produces a second reflectance peak at approximately 385 nm, accounting for the observed reflection in the ultraviolet. Other scales have a similar thickness of chitin but lack the air gap and thus produce a dull purple reflection. This novel mechanism provides the spiders with two colour signals, both of which are important in mating displays.
Land
Michael F
MF
Department of Biology and Environmental Science, University of Sussex, Brighton, UK. m.f.land@sussex.ac.uk
Horwood
Julia
J
Lim
Matthew L M
ML
Li
Daiqin
D
D000818:Animals; D002686:Chitin / Q000737:chemistry* / Q000528:radiation effects; D003116:Color; D008297:Male; D046529:Microscopy, Electron, Transmission; D008857:Microscopy, Interference; D008962:Models, Theoretical; D013112:Spiders / Q000033:anatomy & histology*; D014466:Ultraviolet Rays
D002686:Chitin