Cerci absent in which insect order?

Cerci is absent in Psocoptera and Hemiptera insect order.
Cerci (singular cercus) are paired appendages on the rear-most segments of many arthropods, including insects and symphylans.
Psocoptera are a paraphyletic group of insects that are commonly known as booklice, barklice or barkflies. The abdomen has nine segments and no cerci.
Hemiptera is an order of insects, commonly called true bugs and they lack cerci.