In laboratory experiments we compared the functional response of Lysiphlebus testaceipes (Cresson) (Hymenoptera Braconidae) at two constant temperatures (20 vs 28[degree]C) using Aphis gossypii Glover (Rhynchota Aphididae) as host. Ten experienced females were individually exposed for 30 minutes to 5, 10, 25, 50 and 100 aphid nymphs per leaf (corresponding to 0.4, 0.8, 2, 4, 8 specimens/cm2) in a petridish. Four days after the aphid exposure all nymphs of A. gossypii were dissected to assess the parasitism by detecting larvae of the parasitoid. At 20[degree]C L. testaceipes showed a II type functional response, but at 28[degree]C a type III. The equations showed R values of 0.44 for 20[degree]C and 0.62 for 28[degree]C. The curve showed a plateau at 20 and 28[degree]C for 10 and 14 aphids parasitized respectively: the point of inflexion of the sigmoid model of parasitism (type III) at 28[degree]C was about 16 aphids/leaf. The max number of aphids parasitized was at the density of 100 aphids/leaf at 20[degree]C and 50 aphids/leaf at 28[degree]C. Comparing the two temperature tested, L. testaceipes parasitized significantly more aphids at 28[degree]C than at 20[degree]C for the densities of 25 and 50 hosts/leaf (Mann-Whitney test, P<0.05). The percentage of females landing on leaves, the percentage of females contacting the host and the percentage of females ovipositing were significantly higher at 28[degree]C vs. 20[degree]C at a density of 5 hosts per leaf ([chi]2 test, P<0.05). none