DOI: 10.5061/dryad.ffbg79csk
title: CV and colony data vespid mandible wear

description: Key structures of insects, such as their mandibles, become worn by the use
 and this leads to performance constraints, increase of metabolic costs,
 and decrease of individual’ both lifespan and survival. Studying this
 phenomenon is interesting in species that build nests as it demands a
 significant amount of mandible labor; however, the effect of this
 selective factor is less obvious in species like social vespids that
 perform different tasks at different ages. By comparing mandible wear
 between individuals of different ages in 18 colonies of 13 species of
 neotropical social wasps (Vespidae: Polistinae), we aimed to understand
 (1) the distribution of mandible wear across ages, and (2) the association
 between colony size and the coefficient of variation of mandible wear as
 an indicator of specialization. Despite a general positive trend between
 mandible wear and age, there are numerous exceptions and no age seems to
 concentrate this phenomenon. Mandible wear variation was evenly
 distributed throughout the worker ages, and was not correlated with colony
 size. Our study suggests that individuals distribute mandible demanding
 tasks throughout their life to reduce structural attrition which may
 improve worker’s general output. We proposed that, to extend both life
 expectancy and general performance of the workers, wasps may spread the
 more demanding tasks over longer and less intense periods.
description: We studied 18
 colonies of 13 species of neotropical Polistinae wasps selected as
 representatives of major clades of the neotropical Polistinae phylogenetic
 hypotheses (Wenzel and Carpenter 1994; Piekarski et al. 2018; Menezes et
 al. 2020). The number of individuals studied per nest were as follows:
 <i>Mischocyttarus</i> sp (n=15), <i>Polistes</i>
 <i>erythrocephalus</i> (nest A, n=15; nest B, n=12; nest C,
 n=15), <i>Agelaia</i> <i>pallipes</i> (n=13),
 <i>Parachartergus</i> <i>apicalis</i> (n=15),
 <i>Parachartergus</i> <i>fraternus</i> (n=16),
 <i>Synoeca</i> <i>septentrionalis</i> (n=14),
 <i>Metapolybia</i> <i>aztecoides</i> (n=12),
 <i>Protopolybia</i> <i>exigua</i> (n=13),
 <i>Charterginus</i> <i>fulvus</i> (n=15),
 <i>Polybia</i> <i>occidentalis</i> (nest A, n=14;
 nest B, n=15; nest C, n=15), <i>Polybia</i>
 <i>velutina</i> (n=14), <i>Polybia</i>
 <i>gorytoides</i> (n=14), and <i>Polybia</i>
 <i>emaciata</i> (nest A, n=9; nest B, n=14). We studied a
 total of 250 individuals. We avoid within-colony sampling bias since we
 captured the nests at night with all individuals using a plastic bag.
 After collection individuals were transferred to 96% ethanol.
 We dissected
 mandibles from the individuals using a Leica S8APO stereomicroscope.
 Mandibles were cleaned using cavitation for 2 min at 26°C with an
 ultrasonic cleaner FS20D (Fisher Scientific), then they were dehydrated by
 soaking in ethanol 96% for 3min and subsequently transferred to Xylol for
 10 min. Gold-coated mandibles were photographed in a mesial position using
 a scanning electron FEI Quanta200 microscope at 25-30 kV (Fig 1).
 Measurements were taken from scaled SEM images using ImageJ version 1.50b
 (https://imagej.nih.gov/ij/). Every measurement is the mean of the left and right mandibles of each individual. Mandible terminology follows (Silveira and dos Santos 2011). <b>Variables</b> <b>Species codes:</b><i> </i>Mis=<i>Mischocyttarus</i> sp., P.rA, P.rB, P.rC =<i>Polistes</i> <i>erythrocephalus</i> three colonies A,B,C, A.pal=<i>Agelaia</i> <i>pallipes</i>, Par A=<i>Parachartergus</i> <i>apicalis</i>, Par B=<i>Parachartergus</i> <i>fraternus</i>, S.sp= <i>Synoeca</i> <i>septentrionalis</i>, Mt=<i>Metapolybia</i> <i>aztecoides</i>, Pro=<i>Protopolybia</i> <i>exigua</i>, Char=<i>Charterginus</i> <i>fulvus</i>, P.ocA, P.ocB, P.ocC=<i>Polybia</i> <i>occidentalis </i>three nests A,B,C, P.vl=<i>Polybia</i> <i>velutina</i>, P.gor=<i>Polybia</i> <i>gorytoides</i>, and P.mA, P.mB= <i>Polybia</i> <i>emaciata </i>two nests A,B. A, B and C letters refer to different nests within a species. <b>Csize:</b> refers to the number of individuals recorded from the colonies studied <b>Age:</b> We use individual´s wear at the distal margin of the wings as an indicator of both relative age and shifting from within colony activities (young) to the foraging activity stage (old). A third intermediate category (middle) was used as indicator of the initial stages of foraging activities. <b>CV:</b> We used the coefficient of variation (CV) of mean denticle wear per age within a colony as indicator of task specialization. CV was calculated as the ratio between standard deviation and the average values per nest multiplied by 100.