Summary 0[ We tested a set of hypotheses to predict egg!laying behaviour in Aedes triseriatus in the _eld in Massachusetts[ These hypotheses re~ect three main themes] females avoid competitive or predatory threats to their larvae^females judge larvae or eggs as cues to future permanence or productivity within a treehole^and females are either opportunistic ovipositors\ or hedge their bets by scattering their eggs in multiple habitats[ We predicted that mosquitoes might vary in their response depending on whether their o}spring will hatch immediately or enter diapause and hatch the next year[ 1[ We stocked arti_cial treeholes with larvae at four densities ranging from 9 to 89 larvae per habitat for four trials in 0881 and eight trials in 0883[ In 0881\ we added predatory Anopheles barberi larvae to half the replicates of each density level[ In 0883\ we tested for an interaction between egg and larval density by stocking additional traps with eggs in batches of 9\ 19 and 199\ and larvae in densities as in the previous trials[ 2[ The population revealed a signi_cant interaction between time of year and larval density[ More eggs accumulated in traps stocked with fewer larvae "9 or 04# early in the season\ but females showed a slight positive response to higher densities "34 or 89# later on\ after their o}spring were all likely to enter diapause[ These results suggest that potential ambiguities of larval cues\ with indications of habitat permanence as well as adversity of future competition\ are resolved by females[ Females did not respond di}erentially to the predatory Anopheles barberi larvae[ 3[ The estimated batch size obtained in oviposition traps did not di}er from the fecundity of _eld!caught females allowed to oviposit under con_nement in laboratory vials\ suggesting that bet!hedging by scattering of eggs among multiple habitats did not occur[ 4[ An unexpected result\ a positive response to higher egg densities\ is discussed in light of studies on other insects[ This result con~icts with our predictions based on females choosing less competitive environments for their larvae and also con~icts with previously published accounts of avoidance of eggs in this species[ Preference for habitats with conspeci_c eggs might be explained if eggs re~ect habitat stability or if larvae gain an advantage from being in an aggregation[ Neither hypothesis is resolved by the present study[

The colonial marine hydroid, Hydractinia echinata, exhibits a wide range of growth morphologies during ontogeny, from sheet-like colonies of uniform ectodermal mat to colonies which produce complex networks of stolons. Colony ontogeny was quantified under uniform environmental conditions for 70 colonies of H. echinata, with data collected on the growth rates of the three major colony parameters: mat tissue, stolon tissue, and polyps. Analysis of the relative growth rates of the tissues clearly illustrates that variability in colony form between colonies can be attributed to continuous variation in just one of the parameters governing colony ontogeny.

Rates of continuous phosphorus release by individual Daphnia magna (0.3 – 0.9 mg dry weight) were measured using high performance liquid chromatography components in conjunction with a specially designed incubation flow cell. Within the temporal resolution of the technique (3 min), phosphorus release often appeared pulsed rather than only steady. We found significant variation in release rates among the different stages of an individual's parthenogenetic reproductive cycle. Rates observed for animals carrying more mature embryos were lower than those earlier in the reproductive cycle. Rates of phosphorus release observed at and after ecdysis averaged 6.7 times higher than rates observed at other times.Key words: phosphorus, excretion, reproductive stage, ecdysis, Daphnia magna