Abstract: Iroko gall bug, Phytolyma lata (Homoptera; Psylidae) is a major insect pests militating against cultivation of Milicia exceslsa (Iroko) in many parts of West Africa. The reproductive and developmental biology was studied to give an insight on the management approach that could be adopted for it. The study was conducted on 6 month-old iroko seedlings in the laboratory following standard procedure at 27-32±0.3°C and 75-80% relative humidity and 12:12 photoperiod. Developmental period, sex ratio, fecundity, oviposition period and adult longevity were assessed. Adult females Phytolyma lata were oviparous under laboratory condition with; pre-oviposition period (1.40±0.54 days), oviposition periods (4.00±1.22 days), fecundity (41.20±5.35/female), incubation period (5.8±0.54 days) and 95% egg viability. There were five nymph instar stages. The body width and head width of female were significantly larger than male (p>0.05).The average growth rate for the five instars was 1.48. The average life cycle of Phytolyma lata was 17.55±0.97 days and the sex ratio was 1:1.45 in favour of females. There was significant (p<0.05) correlation (r = 0.973) between the stages of nymphal development and the head width. Mated and unmated male lived significantly (p<0.05) shorter than mated female unmated female under laboratory condition.