Iridescent: a surface which reflects the prismatic hues.
Iridicolor: any color so broken up as to reflect the prismatic hues.
Iris: the circle which, in an ocellate spot surrounds the pupil.
Irised: with rainbow colors.
Iris-pigment: = iris tapetum.
Iris tapetum: the pigment layer of the compound eye just below the crystalline cone.
Irregular: unequal, curved, bent or otherwise twisted or modified without order or symmetry, e.g. certain antennae.
Irrorate: marked with minute points; freckled.
Isabelline -us: pale yellow with some red and brown [chronic lemon with a little carmine and roman sepia].
Ischia: = pleura; q.v.