Printed in Great Britain SYMMETRICALLY ORGANIZED DORSAL UNPAIRED MEDIAN (DUM) NEURONES AND FLASH CONTROL IN THE MALE FIREFLY, PHOTURIS VERSICOLOR

1. Male fireflies of the species Photuris versicolor produce a species-typical triple-pulsed flash which is used as a courtship signal. The neural anatomy was examined to determine if this complex behaviour could be attributed to the organization within the central nervous system. 2. The lantern is innervated primarily by the two most posterior abdominal ganglia. Bilateral roots from these ganglia form a symmetrical pattern of innervation to both sides of the lantern tissue. With minor exceptions, this pattern is similar to that described for other firefly species. 3. The neural organization within the lantern ganglia was determined by back-filling the roots with cobalt or Lucifer Yellow CH, and then examining the ganglia in whole mount. Clusters of three or four large dorsal unpaired median (DUM) neurone somata, each sending bilateral processes out of the lantern roots, were found in both lantern ganglia. 4. The DUM neurone axons bifurcate several times and ramify throughout the dorsal surface of the lantern tissue. More than one DUM neurone ma