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The American cockroach (Periplaneta americana) was used to test 14 DDT analogs for their ability to cause a) death and b) repetitive firing in the abdominal nerve cord. P,p' -DDT, p,p' -DDD, p,p' -methoxychlor, and o,p -DDT were all found to induce repetitive firing in the nerve cord after a twice threshold stimulus, but only p,p' -DDT, p,p' -DDD, and p,p' -methoxychlor produced mortality within 4 days from injection of the pesticides. Also, cockroaches exposed to sublethal doses of p,p' -DDT and p,p' -methoxychlor were found to exhibit repetitive firing in the abdominal nerve cord three weeks after injection of the pesticide. The 'cause and effect' relationship between neuroexcitation and lethality is therefore questioned, at least in the case of cockroaches.