DOI: 10.5061/dryad.d7wm37px7
title: Food quality effects on instar-specific life histories of a holometabolous insect

description: It is a long-standing challenge to understand how changes in food
 resources impact consumer life history traits and, in turn, impact how
 organisms interact with their environment. To characterize food quality
 effects on life history, most studies follow organisms throughout their
 life cycle and quantify major life events, such as age at maturity or
 fecundity. From these studies, we know that food quality generally impacts
 body size, juvenile development, and life span. Importantly, throughout
 juvenile development, many organisms develop through several stages of
 growth that can have different interactions with their environment. For
 example, parasitoids typically attack larger instars, whereas larval
 insect predators typically attack smaller instars. Interestingly, most
 studies lump all juvenile stages together, which ignores these ecological
 changes over juvenile development.   We combine a cross-sectional
 experimental approach with a stage-structured population model to estimate
 instar-specific vital rates in the bean weevil, Callosobruchus maculatus
 across a food quality gradient. We characterize food quality effects on
 the bean weevil’s life history traits throughout its juvenile ontogeny to
 test how food quality impacts instar-specific vital rates. Vital rates
 differed across food quality treatments within each instar; however, their
 effect differed with instar. Weevils consuming low quality food spent 38%,
 37% and 18% more time, and were 1%, 8% and 60% smaller than weevils
 consuming high quality food in the second, third and fourth instars,
 respectively. Overall, our results show that consuming poor food quality
 means slower growth, but that food quality effects on vital rates, growth
 and development are not equal across instars. Differences in life history
 traits over juvenile ontogeny in response to food quality may impact how
 organisms interact with their environment, including how susceptible they
 are to predation, parasitism, and their competitive ability.
description: Four-day old eggs collected from stock
 <i>Callosobruchus maculatus</i> females were transferred to
 artificial seed pulses (pellets) for the three pellet quality treatments
 (100%, 95%, and 90% black-eye pea flour). Beginning on day 5 of the
 experiment, (i.e. 5-day old weevils), a single pellet was removed from the
 environmental growth chamber each day for 45 days (i.e. 50 days of weevil
 development from hatching) from each treatment in each replicate. Sampled
 pellets were placed in a -10°C freezer to stop growth and development of
 the larva, giving us cross-sectional data on development and survival
 every 24 h. We retrieved the larvae from each frozen pellet using a
 scalpel under a dissecting microscope. The experiment was replicated 40
 times, such that the total number of sampled larvae (40 replicates X 46
 days X 3 treatments) was: 5,520. For each dissected
 pellet, we noted survivorship (i.e. whether an individual survived until
 its freeze date), identified larval instar (L1, L2, L3 and L4) by counting
 the number of head capsule molts recovered during dissection, measured
 larval head capsule width at its largest width, and quantified larval dry
 mass. Samples were dried in a drying oven at 76<b>°</b>C for
 72 hours. Dry mass was measured three times and the average of these three
 measurements was used for all analysis.
description: <strong>Index of variables</strong>
 Dataset: Counts Column 1:
 age - the age of the individual in days Column 2: trt -
 the pellet quality treatment, 90 = 90% blackeye pea flour:10% filler, 95 =
 95% blackeye pea flour:5% filler, and 100 = 100% blackeye pea
 flour Column 3: stage - the stage of growth of each
 individual, L1 = 1st instar, L2 = 2nd instar, L3 = 3rd instar, L4 = 4th
 instar, L5 = pupa, L6 = adult Column 4: counts - the
 number of individuals alive in each stage of development on each day of
 development summed across all 40 replicates. 
 Dataset: Master Column 1:
 trt - the pellet quality treatment, 90 = 90% blackeye pea flour:10%
 filler, 95 = 95% blackeye pea flour:5% filler, and 100 = 100% blackeye pea
 flour Column 2: age - the age of the individual in
 days  Column 3: hcw6X - the head capsule width,
 measured in micrometer ruler units at 6X the magnification, where each
 ruler unit at 1X the magnification equals 0.001mm. 
 Column 4: dead - identified which individuals were declared dead
 upon sampling, where 0 = alive, and 1 = dead Column 5:
 stage - the stage of growth of each individual, L1 = 1st instar, L2 = 2nd
 instar, L3 = 3rd instar, L4 = 4th instar, L5 = pupa, L6 = adult
 Column 6: mass - the average drymass of each individual measured
 in miligrams Column 7: sex - indication of male or
 female for individuals that reached the adult stage. Note: sex could be
 determined for some individuals in the pupal stage. 
 Column 8: burrowed - indication of whether an individual
 successfully burrowed into the pellet from the egg on the surface of the
 pellet, where 0 = did not burrow, 1 = burrowed. Note: individuals that did
 not burrow were removed from our analyses on head capsule width and dry
 biomass.