AbstractAn account is given of the way the temperature‐mediated processes of development and locomotor activity in insects interact with the availability of essential resources to reduce lifetime fecundity below the potential predicted from laboratory performance. Current work on the sheep blowfly, Lucilia cuprina, is used to illustrate the points made wherever possible.Brief reviews of the ecologically important relationships between rate of development and temperature and level of activity and temperature are presented. The ways in which such laboratory‐derived relationships may be applied in the interpretation of field results are described and discussed. The notions of time as a resource and of protein‐food, mates and oviposition sites as limiting resources are presented and these provide the basis of a time/resource/fecundity mechanism limiting reproductive performance during the life‐time of a female insect. Field and laboratory data are used to show the potentiality of such a mechanism for reducing life‐time fecundity in the shee