This work deals with the study of the biology of Glena unipennaria unipennaria (Guenée, 1857) (Lepidoptera, Geometridae). The larvae are defoliators and considered as pest of economical importance on homogeneous plantation of Eucalyptus spp. (Myrtaceae). The insects were reared in laboratory conditions (Temperature: 25±3°C; RH: 70±10%; 12 - hourphotoperiod). The larvae were reared on leaves of Eucalyptus grandis (Hill) Maiden. The following parameters were determined: period and viability of the egg, larva, pre-pupa and pupa stages;number and the length of the larval instars and leaf consumption of the larval stage, adult longevity and sex ratio. The measurements of the read capsules of the larvae; length and width of the pupa and wing span of the adults were taken. Aspects related to ethology and external morphology were observated as well.