Many animals lay their eggs in clusters. Eggs on the periphery of clusters can be at higher risk of mortality. We asked whether the most commonly occurring clutch sizes in pentatomid bugs could result from geometrical arrangements that maximize the proportion of eggs in the cluster’s interior. Although the most common clutch sizes do not correspond with geometric optimality, stink bugs do tend to lay clusters of eggs in shapes that protect increasing proportions of their offspring as clutch sizes increase. We also considered whether ovariole number, an aspect of reproductive anatomy that may be a fixed trait across many pentatomids, could explain observed distributions of clutch sizes. The most common clutch sizes across many species correspond with multiples of ovariole number. However, there are species with the same number of ovarioles that lay clutches of widely varying size, among which multiples of ovariole number are not over-represented. In pentatomid bugs, reproductive anatomy appears to be more important than egg mass geometry in determining clutch size uniformity. In addition, within this group of animals that has lost most of its variation in ovariole number, clutches with a broad range of shapes and sizes may still be laid. 

Part of the dataset was collected from different research laboratories studying stink bugs (Hemiptera: Pentatomidae) that recorded clutch sizes laid by their bugs in the course of their research. The other dataset was collected from analysis of photographs of stink bug eggs from online sources and photographs taken by study co-authors. The R code provided on Zenodo ( https://doi.org/10.5281/zenodo.6557606 ) makes use of the .csv files to generate figures and analyses for this paper, which is in press at the American Naturalist currently.

R code required to process the data is available here: https://doi.org/10.5281/zenodo.6557606