The oral ld50 value for cypermethrin is 247 mgkg compared to 5000 mgkg for hexaflumuron therefore what is the more toxic of these two pesticide?

Cypermethrin, assuming the LD50s for the two chemicals are for the same period of time. LD50 is the lethal concentration where half of the individuals die in a given time period. Higher numbers mean that is takes more of the chemical to kill organisms, whereas lower numbers mean it takes less of the chemical to kill organisms. LD50s depend on what animal was used in the experiment.