Intraspecific competition between different aged larvae of Agromyza frontella (Rondani) (Diptera: Agromyzidae): advantages of an oviposition-deterring pheromone

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Abstract
In laboratory studies evaluating the effects of intraspecific competition between A. frontella larvae of different ages, individuals starting 24 or 48 h before other larvae within the same leaflet largely escaped the negative effects of competition. However, larvae starting development later experienced a higher incidence of mortality and reduced pupal weight. An oviposition-deterring pheromone laid down by ovipositing A. frontella females would only have to remain effective for 24 h to confer a competitive advantage to the 1st individual developing within the leaflet. In 2 separate field tests this proved to be the case, with active pheromone remaining for > 24 h under both hot and rainy conditions. There has been some doubt concerning the adaptive value of certain oviposition-deterring pheromones under field conditions because of their water-soluble nature. The required active life of an oviposition-deterring pheromone may be considerably shorter than previously thought, and thus their persistence, even for shorter periods, may be adequate to reduce intraspecific competition in natural populations.