The house fly, Musca domestica transmits many diseases to humans, so that controlling it without
side effects on human health is extremely important. Therefore, the current study aimed to
compare the toxicity of tested chitin synthesis inhibitors (CSIs) lufenuron, flufenoxron, and hexflumuron
against 3rd instar larvae of the house fly, and to assess the lethality effects by serial
concentrations (1000, 500, 250 & 125ppm) of each tested compound on the developmental parameters
and growth indices of the immature stages of M. domestica. The least toxicity values
of sub-lethal concentrations (LC25, LC50 & LC75) displayed for lufenuron (158.23, 332.46 &
698.56, respectively). Also, hexaflumuron scored (64.06ppm at LC25), followed by flufenoxuron
(140.95 & 283.62ppm at LC50 & LC75, respectively). Flufenoxuron was the most toxic, followed
by hexaflumuron and lufenuron. CSIs showed a toxic efficiency on 3rd instar larvae of M. domestica
by decreasing developmental and growth indices rates at higher concentrations of each
one. Flufenoxuron exhibited a marked significant decrease in larval development and growth index
rates (15.50 & 2.71% at 1000ppm, respectively), highest water loss (69.79%) compared to
hexaflumuron and lufenuron. Flufenoxuron was the most toxic one against pupae as compared to
others, it prolonged pupal duration (14.71day) and induced pupal water loss (53.77%), its pupation,
developmental and weight rate reduced (17.5 & 6.8%, & 53.77mg respectively). But, growth
index did not cause mortality with the highest concentration. Adult emergence displayed
non-adult emergence and a high percentage of the malformation rate at 1000ppm when treated
with flufenoxuron compared to other compounds.