How to escape from insect egg parasitoids: a review of potential factors explaining parasitoid absence across the Insecta

N.E. Fatouros*, A. Cusumano, F. Bin, A. Polaszek*, J.C. van Lenteren

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The egg is the first life stage directly exposed to the environment in oviparous animals, including many vertebrates and most arthropods. Eggs are vulnerable and prone to mortality risks. In arthropods, one of the most common egg mortality factors is attack from parasitoids. Yet, parasitoids that attack the egg stage are absent in more than half of all insect (sub)orders. In this review, we explore possible causes explaining why eggs of some insect taxa are not parasitized. Many insect (sub)orders that are not attacked by egg parasitoids lack herbivorous species, with some notable exceptions. Factors we consider to have led to escape from egg parasitism are parental egg care, rapid egg development, small egg size, hiding eggs, by e.g. placing them into the soil, applying egg coatings or having thick chorions preventing egg penetration, eusociality, and egg cannibalism. A quantitative network analysis of host-parasitoid associations shows that the five most-speciose genera of egg parasitoids display patterns of specificity with respect to certain insect orders, especially Lepidoptera and Hemiptera, largely including herbivorous species that deposit their eggs on plants. Finally, we discuss the many counteradaptations that particularly herbivorous species have developed to lower the risk of attack by egg parasitoids.

Original languageEnglish
Number of pages1
JournalProceedings. Biological sciences
Volume287
Issue number1931
DOIs
Publication statusPublished - 29 Jul 2020

Keywords

  • egg deposition
  • egg protection
  • herbivory
  • hymenoptera
  • oviposition site
  • parental care

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