Data file "Kivelä et al._MR data" contains respirometric data on fourth- and fifth-instar Pieris napi larvae. Sami M. Kivelä (sami.kivela@oulu.fi) answers questions regarding the data. The data file contains four data sheets. The sheet "Experiment" includes data from the respirometry group, and it includes the following columns: family -- identity of the mother of the larva ID -- individual identity time -- timing of the measurement (proportion of the day elapsed since midnight) instar -- instar of the larva (IV [fourth] or V [fifth]) growth -- a variable indicating whether the observation is from the growth period ("yes") or from the post-growth period ("no") frass -- the number of frass produced during the measurement movement -- movement (number of crossing the borders between three equal-sized parts of the measurement chamber) during the measurement sex -- sex of the larva O2 -- oxygen consumption rate ([ml O2] / h) during the measurement CO2 -- carbon dioxide production rate ([ml CO2] / h) during the measurement RQ -- respiratory quotient MR -- metabolic rate (mW) STN -- signal to noise ratio for O2 consumption rate day -- days since the first measurement of the individual in question mass -- mass (mg) of the larva at the time of respirometric measurement RQ can be calculated by dividing CO2 by O2. The sheet "Control" includes data from the control group, and it includes the following columns: family -- identity of the mother of the larva ID -- individual identity instar -- instar of the larva (IV [fourth], V [fifth], prepupa [not a separate instar in the strict sense] or pupa) sex -- sex of the larva day -- days since the first measurement of the individual in question mass -- mass (mg) of the larva The sheet "Body composition" includes data from the body composition analysis. It includes the following columns: instar -- instar of the larva (IV [fourth] or V [fifth]) fresh mass -- fresh mass (mg) of the larva relative water content -- percentage of water (% of fresh mass) relative lipid content -- percentage of lipids (% of fresh mass) The sheet "Starvation" includes data from the starvation control, with the following columns: ID -- individual identity instar -- instar of the larva (IV [fourth] or V [fifth]) starvation time -- time (h) since the beginning of starvation msCO2 -- mass-specific carbon dioxide production rate ([ml CO2] / g / h) mass -- mass (mg) of the larva