Toxicosis of mirex for chick embryos and chickens hatched from eggs inoculated with mirex.

Mirex, a hydrocarbon, was mixed with corn oil and injected into chick embryos to test its toxic effect. At a concentration of 0 05 mg mirex/egg, embryo mortality was 40%, at 0.5 mg/egg, mortality was 49%, and at 5.0 mg/egg, mortality reached 81%. Mortality of control eggs injected with corn oil alone was 36%. The body weights of newly hatched chickens and of 4-week-old chicks were not different from those of controls. No clinical signs of disease were seen during the 4 weeks of observation. However, liver weights were increased at all 3 dosages when the birds were killed at 4 weeks, but spleen and bursal weights were not. The results support the decision to discontinue the use of mirex as a pesticide in the environment for controlling the fire ant (Solenopsis sp.) until a better means of presenting it can be found.