Leioproctus constrictus, or Leioproctus (Colletellus) constrictus, is a species of bee in the family Colletidae and subfamily Colletinae. It is endemic to Australia. It was described by entomologist Remko Leijs in 2018.
Etymology The specific epithet constrictus is an anatomical reference to the strongly depressed post-gradular areas of T2–3 in both sexes.
Description The female holotype body length is 5.9 mm, head width 1.9 mm; male allotype body length is 4.2 mm, head width 1.52 mm. Integumental colouration is mainly black and brown. The hair is whitish.
Distribution and habitat The species occurs in Western Australia. The type locality is 16 km west-north-west of Merredin.
Behaviour The adults are flying mellivores. Flowering plants visited by the bees include Grevillea paradoxa, Grevillea petrophiloides, Eremophila pantonii and Ecdeiocolea monostachya.
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