author={David L. Stern and William A. Foster},
  journal={Biological Reviews},
1. Defensive individuals, termed soldiers, have recently been discovered in aphids, Soldiers are typically early instar larvae, and in many species the soldiers are reproductively sterile and morphologically and behaviourally specialized. 2. Since aphids reproduce parthenogenetically, we might expect soldier production to be more widespread in aphids than it is. We suggest that a more useful way to think about these problems is to attempt to understand how a clone (rather than an individual) should invest in defence and reproduction. 3. Known soldiers are currently restricted to two families of aphids, the Pemphigidae and Hormaphididae, although they are distributed widely among genera within these families. We discuss the use of a phylogenetic perspective to aid comparative studies of soldier production and we demonstrate this approach using current estimates of phylogenetic affinities among aphids. We show that the distribution of soldier production requires a minimum of six to nine evolutionary origins plus at least one loss. [] Key Result 4. At least four main types of soldiers exist and we present and discuss this diversity of soldiers. 5. Most soldier-producing species produce soldiers within plant galls and we discuss the importance of galls for the evolution of soldiers. 6. We summarize the evidence on the interactions between soldiers and predators and between soldier-producing aphids and ants. 7. We present an optimality model for soldier investment strategies to help guide investigations of the ecological factors…

The evolution of soldier reproduction in social thrips

This is the first study to analyze the social-evolutionary trajectories of reproductive, behavioral, and morphological differentiation in the context of a species-level phylogeny and suggests that this difference in evolutionary routes to eusociality between taxa with soldiers andTaxa with foraging workers was driven by a weaker trade-off between helping and reproducing, and a greater ability of the helpers to withstand reproductive domination, in taxas with soldiers.

Caste allometries in the soldier-producing aphidPseudoregma alexanderi (Hormaphididae: Aphidoidea)

A morphometric study of soldiers and normal first-instar larvae of Pseudoregma alexanderi finds further support for an earlier finding that soldiers fall into two size categories, majors and minors, although both types of soldiers appear to follow the same allometry.

Soldiers effectively defend aphid colonies against predators in the field

To study the effectiveness of soldiers of the gall-forming aphid, Pemphigus spyrothecae Pass.

Maintenance of soldier-producing aphids on an artificial diet.

Behavior and morphology of monomorphic soldiers from the aphid genus Pseudoregma (Cerataphidini, Hormaphididae): implications for the evolution of morphological castes in social aphids

The discovery of a novel soldier type in an undescribed species of Pseudoregma that is morphologically similar to P. bambucicola is reported, and the first example of a possible within-instar age polyethism in soldier-producing aphids is reported.

Clonal mixing in the soldier‐producing aphid Pemphigus spyrothecae (Hemiptera: Aphididae)

Observations suggest that although soldiers migrate regularly and can moult and reproduce within foreign galls, clonal mixing in this species is generally low and is unlikely to provide a barrier to the evolution of investment by the aphid clones in an altruistic soldier caste.

Soldier behaviour and division of labour in the aphid genus Pemphigus (Hemiptera, Aphididae)

A test for quantitatively measuring the defensive behaviour of individual aphids of the gall generations of the genus Pemphigus found that the first instars were always the most likely to be aggressive, and later instars also showed significant levels of aggression in all the soldier-producing species.

Behaviour, morphology and the division of labour in two soldier-producing aphids

The data suggest that the caste structure of the social aphids is more complex than expected, and is perhaps more similar to that of thesocial Hymenoptera.

Soldiers with large weapons in predator-abundant midsummer: phenotypic plasticity in a eusocial aphid

Results indicate that C. japonica aphids not merely have distinctive reproductive—and soldier castes, but also produce differentially armed soldiers in a habitat with temporally changing predation risks.

Venomous protease of aphid soldier for colony defense.

The soldier-specific cathepsin B gene showed an accelerated molecular evolution probably caused by the action of positive selection, which had been also known from venomous proteins of other animals.



A phylogenetic analysis of soldier evolution in the aphid family Hormaphididae

  • D. Stern
  • Biology
    Proceedings of the Royal Society of London. Series B: Biological Sciences
  • 1994
A mtDNA based phylogeny for the Hormaphididae is presented and the hypothesis that soldiers in the tribe Cerataphidini produced during two points in the life cycle represent independent origins are tested, and the results support this hypothesis.

Territorial behaviour of Pemphigus gall aphids

The existence of a defended micro-territory, the production of a floater population of individuals displaced through competitive interactions, and the differential mortality of residents and floaters which favours the evolution of territorial behaviour are quantified.

Altruistic housekeeping in a social aphid

  • T. BentonW. Foster
  • Biology
    Proceedings of the Royal Society of London. Series B: Biological Sciences
  • 1992
It is shown experimentally that the soldier caste of an aphid, the gall-forming Pemphigus spyrothecae, fulfils a second, non-defensive, altruistic role: the soldiers actively clean their gall.

The Evolution of Aphid Life Cycles

The life cycles of aphids are among the most remarkable of any animal group. They include parthenogenetic and sexual generations, elaborate polyphen­ isms, and obligate shifting between unrelated

The evolutionary biology of sterile soldiers in aphids.

  • Y. Itô
  • Biology
    Trends in ecology & evolution
  • 1989

Eusociality in Australian gall thrips

The presence of eusociality is reported in a second haplodiploid insect taxon, the order Thysanoptera, which provides remarkable new opportunities for analysing the causes of the evolution of eUSociality.

The life cycle and natural history of the tropical aphid Cerataphis fransseni (Homoptera: Aphididae: Hormaphidinae), with reference to the evolution of host alternation in aphids

It is demonstrated that this aphid migrates between trees of Styrax benzoin and various species of palms; palm-feeding populations have previously been known as C. variabilis and C. palmae, which now become synonyms of C. fransseni.

Enemy recognition and defence within trophobiotic associations with ants by the soldier caste of Pseudoregma sundanica (Homoptera : Aphidoidea)

The haemolymph of aphids being attacked by predators is perceived by the aphid soldiers after immediate contact and releases their defensive behaviour against the intruder and the same mechanism of releasing attacks against potential aphid predators could be demonstrated experimentally.

Genetic relatedness in primitively eusocial wasps

New estimates of relatedness from 14 species of polistine wasps lacking morphological castes are reported, showing that relatedness is always fairly high, in striking contrast to the situation in some species with morphologicalCastes.


The aggregating form of the anemone Anthopleura elegantissima often lives in closely packed groups composed of genetically identical individuals. These clonal aggregations remain separated from each