Larvae of Megaselia scalaris (Loew, 1866) feed on a wide range of decomposing organic matter and present a great importance to public health. This study evaluated the effect of crude latex extract from Euphorbia splendens var. hislopii (Euphorbiaceae) on post-embryonic development time of M. scalaris under laboratory conditions. The latex was used in its crude lyophilized form, dissolved in distilled water and tested in concentrations of 5 microg/mL, 10 microg/mL and 20 microg/mL. The latex was applied with the aid of an automatic pipette (1 microL/larva) on the newly-hatched larvae. Each group (the three concentrations of latex and the control group) was composed of 50 larvae and fed with 25mg of decomposing horse flesh. The experiment was made in quadruplicate. The observations were recorded daily. The data were submitted to analysis of variance (ANOVA) and Tukey's post hoc-test with a 5% significance level. The post-embryonic development time for all stages (larval, pupal and newly-hatched larvae to adult) tested with all three latex concentrations was significantly shorter than for the control group, but without any significant difference among the different concentrations. The more sensitive stages to the substance were pupal and newly-hatched larvae to adult. The viability was less than 51.5% in the three concentrations of latex in these stages and they were lower than for the control group (67.4% for pupal stage and 64% for newly-hatched larvae to adult). Therefore, it is likely that this substance has influence on the development and viability of these flies and can become a promising agent for insect pest management.