A PHYSIOLOGICAL AGE-GRADING SYSTEM FOR NEOCHETINA-EICHHORNIAE (WARNER) (COLEOPTERA, CURCULIONIDAE), A BIOLOGICAL-CONTROL AGENT OF WATER HYACINTH, EICHHORNIA-CRASSIPES (MART) SOLMS

Neochetina eichhorniae has a meroistic reproductive system composed of a pair of ovaries each subdivided into two tube-like ovarioles, The o varioles consist of two main regions, the distal germarium and the pro ximal vitellarium. The vitellarium houses the developing follicles, wh ich mature sequentially. The two ovarioles in each pair connect proxim ally via the lateral oviducts. The paired ovaries join one another via the common oviduct, Ovarian development involves two distinct phases: a nulliparous (meaning ''no eggs'') phase and a parous (meaning ''wit h eggs'') phase. Each phase undergoes three sequential stages, named N 1, N2, and N3 and P1, P2, and P3 for the nulliparous and parous catego ries, respectively. The degree of maturity of the proximate follicles and the extent of follicular differentiation distinguish the nulliparo us stages. The quantity and quality of follicular relies (and, by asso ciation, the number of egg ovulations) distinguishes the parous phases , The overall condition of the ovaries can be characterized from the n umber of developing follicles in the ovarioles as well as the integrit y of the follicular cellular material, Samples from field populations in Texas revealed distinct seasonal changes in physiological age struc ture and condition of the reproductive system, This physiological age- grading system can be an important tool for assessing age structure an d relative reproductive health of N. eichhorniae populations or other weed biological control agents with similar reproductive systems. (C) 1997 Academic Press.