Published online by Cambridge University Press: 10 July 2009
The internal reproductive system of adult males of Spodoptera littoralis (Boisd.) is described, and changes in colour of a secretion in the ductus ejaculatorius simplex with age and mated status are noted. Virgin males 0–7 days old and mated males 0–7 days after mating were killed and the colour of the secretion in the simplex compared with colour chips in the Munsell book of color (1929–1942). The results showed that the simplex of newly emerged males was colourless or pale yellow, but after two days an orange pigmented secretion had begun to accumulate in 61·3% of males examined. By four days this pigment had darkened to deep red in 96·4% of virgin males. On mating, a portion of this secretion was incorporated into the spermatophore while the rest was passed into the bursa copulatrix of the female, leaving the simplex of newly mated males colourless. There was. however, a gradual re-accumulation of the pigmented secretion after mating through yellow, orange and finally to deep red. This accumulation of the red pigment was slightly slower in the mated males than in virgins, and three days after mating only 29·6% of the males had a red simplex compared with 78·8% of three-day-old virgin males. The potential use of these changes in colour to determine the mated status of field-caught males is discussed.