A mathematical simulation model (Axelsen et al., 1997) was used to sim
ulate the outcome of reproduction experiments with the collembolan Fol
somia fimetaria L. The animals are taken from synchronous cultures, an
d the model was used to assess the impact both of two different ways o
f selecting the individuals for the experiments and the variation in t
he reproduction due to different synchronisation widths and maximum ag
es in the synchronous cultures. Based on the simulations it is recomme
nded to establish a standardised procedure for the selection of test a
nimals from the cultures. The width of synchronisation and the maximum
age in the synchronous culture was not found to affect the results co
nsiderably. However, the age was important because the variation on th
e reproductive output was found to depend on a fixed sex ratio from re
plicate to replicate. This can be obtained when the experimental anima
ls originate from cultures with an age where the animals can be sexed
safely due to morphological differences.