Host-Parasitoid Interactions

by

Jeffrey A. Harvey

• LAST REVIEWED: 08 September 2021
• LAST MODIFIED: 24 July 2013
• DOI: 10.1093/obo/9780199830060-0107

Introduction

Insects are a highly diverse group due to their ability to exploit a wide range of niches. Each plant is attacked by multiple herbivores and these in turn may harbor a bewildering complexity of natural enemies, particularly parasitoids, which are often quite specialized in terms of the host species identity (and stage of attack) of their hosts. Furthermore, these parasitoids have their own parasitoids that attack them, meaning that food webs including these insects may go up to five trophic levels (or even more). Due to their diversity and strong link population dynamics, parasitoids comprise important aspects of ecological communities. Because of this and their potential as biocontrol agents, host-parasitoid dynamics have been a major focus of ecological and evolutionary study since the beginning of the 20th century.

General Overviews

Parasitoids were initially recognized from the order Hymenoptera, but later research showed that a number of families in the Diptera order and one in the Coleoptera order also contain true parasitoids. In describing parasitic insects, the term “parasitoid” was first used in Reuter 1913. His definition referred to an organism that goes through complete metamorphosis and whose larvae are parasitic but whose adults are free living (see Defining Parasitoids). Since that time, the term has been greatly refined to accommodate the plethora of life-history strategies that are found in parasitoids. Some of the most important pioneering research on host-parasitoid interactions was performed by George Salt (Salt 1941) and Stanley Flanders (Flanders 1942 and Flanders 1950), whose early works on development and reproduction are still considered to be of profound importance today. Their studies also influenced later generations of entomologists working on parasitoids. Doutt 1959 wrote the first comprehensive review of insect parasitoids.

• Doutt, Richard L. 1959. The biology of parasitic Hymenoptera. Annual Review of Entomology 4.1: 161–182.

  DOI: 10.1146/annurev.en.04.010159.001113

  The first lengthy article to provide a thorough overview of what was known up until that time about various aspects of the biology and ecology of hymenopterous insect parasitoids.

• Flanders, Stanley E. 1942. Oosorption and ovulation in relation to oviposition in the parasitic Hymenoptera. Annals of the Entomological Society of America 35:251–266.

  Early study detailing, comparing, and contrasting the structure and morphology of parasitoid eggs in different species. Flanders describes differences in the structure of the egg chorion in ecto- and endoparasitoids and the importance of host-feeding or immersion in host fluids on embryogenesis.

• Flanders, Stanley E. 1950. Regulation of ovulation and egg disposal in the parasitic Hymenoptera. Canadian Entomologist 82:134–140.

  DOI: 10.4039/Ent82134-6

  Taking the work of 1942 further, Flanders devised a method of describing the differing egg maturation strategies (ovigeny). This article has inspired many subsequent studies into the reproductive biology of insect parasitoids.

• Reuter, O. M. 1913. Lebensgewohnheiten und Instinkte der Insekten. Berlin: Friendlander.

  First individual (and not a scientist!) to formally describe parasitoids by the criteria of having one stage (the larva) that was predaceous in the host but not the adult.

• Salt, George. 1941. The effects of hosts upon their insect parasites. Biological Reviews 16:239–264.

  DOI: 10.1111/j.1469-185X.1941.tb01103.x

  Salt may have been the greatest early researcher on the development and physiology of insect parasitoids, and his research was well ahead of its time. This study is perhaps the first detailed review of host-related effects on parasitoid development.