This README.txt was created by Keshi Zhang (University of Auckland) and was updated on 23 Jan 2025 GENERAL INFORMATION 1. Zhang K, Schausberger P, Greg H, Zhang Z.-Q. 2026. Older mothers produce offspring with improved development and growth efficiency. 2. Brief abstract Maternal age and diet can influence offspring development and fitness via maternal effects, but how these two factors interact remains poorly understood. We examined how maternal age at oviposition and dietary conditions affect offspring developmental plasticity in an asexually reproduced predatory mite (Amblyseius herbicolus). Mothers were provided either a restricted or abundant prey diet, and their offspring were exposed to varying prey availability and monitored for hatching success, survival to adulthood, developmental time, size at maturity, and prey consumption. We addressed two main questions: How does maternal age affect offspring developmental time and size at maturity and does maternal diet modify the effect of maternal age on offspring? Offspring of older mothers showed increased survival and reduced prey consumption without any compromise in terms of size at maturity. Interactions were found between maternal diet and age on offspring prey consumption and developmental plasticity. Notably, offspring from older, diet-restricted mothers achieved the best overall performance during development. Our study demonstrates that maternal age and diet jointly shape offspring development, and highlights the importance of incorporating maternal age into studies of maternal effects and phenotypic plasticity. 3. Originators Keshi Zhang 4. Contact information School of Biological Sciences, 3A Symonds Street, University of Auckland, Auckland 1010, New Zealand. zhangk@landcareresearch.co.nz 5. Date of data collection May–Sep 2024 6. Geographic location(s) of data collection New Zealand ACCESS INFORMATION 1. Licenses/restrictions placed on the data CC-BY-NC 4.0 (Attribution-NonCommercial) DATA FILES AND VARIABLES 1. f0_life_histories The life history traits of the mothers (f0) under two dietary regimes. • no: subject ID • treat: dietary regimes (Full or Restricted) • con: number of prey eggs consumed during development • ea: egg–adult duration in days • pre: pre-oviposition duration in days • ls: lifespan in days • fec: fecundity (number of eggs laid during lifetime) • ovi: oviposition duration in days • post: post-oviposition duration in days • max: maximum daily oviposition • daily: daily oviposition • adcon: prey consumption during adulthood • dc: daily prey consumption • add: daily prey consumption during adulthood • size: dorsal plate length (µm) 2. f0_con_ovi The daily prey consumption and oviposition of mothers (f0) during their lifetime. • no: subject ID • treat: dietary regimes (Full or Restricted) • day: age after moulting into adults in days • con: number of prey eggs consumed • few: number of eggs laid 3. f0_eggv The egg volume laid by mothers under the two dietary regimes. • mum: subject ID • day: age at oviposition in days • volume: egg volume measured in mm^3 4. f1_life_histories The life history traits of the daughters (f1) under two dietary regimes. • no: subject ID • mum: mother's ID • mage: maternal age at oviposition in days • diet: number of prey eggs given to daughters during immature development • hatch: egg viability (Yes or No) • adult: survival to adulthood (Yes or No) • ea: egg–adult duration in days • con: number of prey eggs consumed during development • treat: maternal dietary treatment (Full or Restricted) • age: maternal age at oviposition (Young or Old) • size: daughter's dorsal plate length (µm) 5. Rcode The R codes used in this study.