DOI: 10.5061/dryad.41ns1rnr4
title: Deterring egg predators with fecal strings is more efficient when eggs are aggregated

description: Predation on insect eggs can be very high and female insects use multiple
 antipredator strategies to reduce egg mortality. Two common strategies are
 to aggregate eggs, that may function to satiate egg predators, and various
 deterrence strategies, such as the addition of fecal strings on top of the
 egg. We tested the hypothesis that these two strategies work best in
 combination, where egg aggregation may strengthen the effect of deterrence
 strategies. We compared egg predation by the predator Paederus riparius
 both within species Galerucella lineola (cleaned eggs versus egg with
 fecal strings), and between the species G. lineola and G. sagittariae
 (where the latter species naturally lack fecal strings). Our findings
 revealed a robust treatment interaction, where fecal strings and egg
 density affected egg survival when exposed to Paederus riparius. Egg
 survival increased with egg density for eggs with fecal strings but was
 constantly low on eggs without fecal strings (cleaned G. lineola eggs or
 G. sagittariae eggs). This study emphasized the need of a combine of
 insect defensive measures to prevent herbivorous insect interactions with
 their natural predators.
description: This is an experimental study performed in petri dishes on egg
 predation by Paederus riparius on Galerucella eggs. Trials included egg
 batches between 2 and 24 eggs, which were exposed to predation for 24
 hours.
description: # Deterring egg predators with fecal strings is more efficient when eggs
 are aggregated
 [https://doi.org/10.5061/dryad.41ns1rnr4](https://doi.org/10.5061/dryad.41ns1rnr4) ## Description of the data and file structure An experiment testing the hypothesis that fecal strings placed by females on insect eggs provide protection against predation. The study was motivated by the observation that some species in Galerucella (Coleoptera: Chrysomelidae) place a fecal strings whereas others do not, but also that eggs in these species are often aggregated. The aim was to evaluate whether the efficiency of the fecal strings also depended on the egg number. Setup: Each trial include an egg batch (2, 4, 8, 12, 16, 20 or 24 eggs) of three types: (a) Eggs of G. lineola that naturally have fecal strings, (b) Eggs of G. lineola that were cleaned and where fecal strings were removed and (c) Eggs of G. sagittariae that naturally lack fecal strings. ### Files and variables #### File: Predator\_experiment.txt **Description:**  ##### Variables * Species: Gl = Galerucella lineola, Gs = Galerucella saggitariae * Treatment: Control = natural; Clean = cleaned eggs (only Gl) * Egg_dens: The number of initial eggs in the petri dish * Consumed: The number of eggs consumed by the predator (Paederus riparius) * Survived: The number of surviving eggs * Prop_cons: The proportion consumed ## Code/software Analyses were run in R, with glmer in the lme4 package: ``` glmer(Survival~Egg\_density*Treatment+(1|Batch),data ``` For this analysis, the data was reformated so that each row was a single egg that survived or was consumed (0/1-variable) and where batch is the trial in the same petri dish. This test models whether the probability of egg survival depends on if the egg has a fecal string, on the number of eggs in the batch, and on the combination of these two.