An Interesting Case of a Bicephalous<i>Tegenaria atrica</i>Nymph

Summary An interesting case of a bicephalous Tegenaria atrica nymph was obtained after using thermal shocks in the form of temperatures of 14 and 32(C acting alternately on spider embryos in the first 10 days of development. An analysis of histological sections made by the paraffin method and stained with haematoxylin and eosin showed the nervous system and two poison glands in the accessory head.