Ulloa, [33]

Uroceridae, [507]

Useless wings, [199], [394], [484], [561]

Uterus, [18], [392]

Vagus nervous system, [120]

Van Rees on metamorphosis, [162], [164]

Variation, [536];

of colour, [252], [288], [304], [308];

in desert Insects, [305];

in ocelli, [267], [395], [536]