Alate production and sex ratio in colonies of the Neotropical termite Nasutitermes corniger (Isoptera; Termitidae)

Abstract

Dissections of 49 entire Nasutitermes corniger (Motschulsky) colonies collected in Panama immediately prior to the nuptial flights give data on numbers, biomass and sex ratio of alates produced by individual colonies. Twenty-six other colonies were collected and dissected in the early period of alate nymph development. Alate nymphs proceed through five instars, spending 5–8 months within the parental colony. Even when comparing colonies of similar size, variation in reproductive output among N. corniger colonies in a population is marked. Mature colonies (neuter population size 50,000–400,000) generally produce 5,000–25,000 alates, although some large colonies had no fertile brood, at least during the year they were censused. On average, colonies which produce alates have 35% of the colony biomass invested in alates (or late instar nymphs) shortly before the nuptial flight. Female N. corniger alates are 1.2–1.4 times heavier (dry weight) than male nestmates. Numerical sex ratio among colonies is skewed toward males, while biomass “investment” sex ratio is not significantly different from 1:1. These data conform to Fisher's amended theory of expected sex ratio.