This review investigates ant–aphid mutualism (trophobiosis), in particular focusing on evolutionary processes in aphids resulting from this interaction. This broad literature review allows us to revise existing views on certain aspects of this mutualism and provide the first timeline of its possible development over a geological timescale. We propose a new classification of ant–aphid mutualism with respect to its ecological characteristics and present new explanations of the development of certain morphological structures of aphids as resulting from adaptation to a trophobiotic relationship with ants. In light of these findings, the presence of the so‐called ‘trophobiotic organ’ in all myrmecophilous aphids is questioned. We review various communication modes between aphids and mutualistic ants and the possible influence of this symbiosis on modifications of aphid life cycles. Recent evidence on the suspected role of endosymbiotic bacteria in the development of mutualism is discussed. Finally, we propose a first timeline of ant–aphid interactions leading to the development of particular adaptations of aphids to mutualism, from general interactions between diverging Aphidomorpha and ants in the late Mesozoic to more specific coevolution between the aphid tribe Fordini and the ant genus Lasius.

Scanning electron microscopy and light microscopy were used to elucidate the morphology of labium and mandibular and maxillary stylets of the aphids Stomaphis quercus (L.) and S. graffii Cholodkovsky. The mechanism of labium shortening associated with feeding process was described as well. Stomaphis quercus and S. graffii have cone-shaped labium of 13 and 10 mm in length, respectively, that strongly extend behind the abdomen. The stylets bundle comprises a pair of mandibular and maxillary stylets which are on average as long as labium. Serial cross sections of labium revealed that the first segment is inverted inside and the second is pulled into it; both segments are shifted into abdomen. This study provides new information on S. quercus and S. graffii mouthparts that may help to understand their feeding behavior.

Wings of Orthezia urticae males were studied. Both ventral and dorsal surfaces of wings were examined under light and scanning electron microscopes. The structure regarded as vein cubitus anterior turned out to be a reinforcement element only. Two elements known as radius sector and media are almost transparent depressions in the wing membrane. Veins at the margin of the fold of the wing anal lobe were not confirmed. Studies indicated a row of sensilla cupola at the beginning of the subcostal ridge.Cross sections of the wing membrane showed a two-layered membrane. The presence of two veins was confirmed in a common stem – subcostal and radius. The change of common stem shape was described. Neither tracheae nor nerves were observed. This is the second paper on cross-sections of wing within Sternorrhyncha.

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Paper presents the phenomenon of thanatosis or death-feigning in selected aphids species. This specific reaction was predominantly analysed on the example of aphid subfamily Lachninae. Individuals of this group were used in experiments, during which a thanatotic response was induced with various results. The response differed from prolonged thanatosis, lasting for several minutes (Eulachnus rileyi), through shrinking behaviour (e. g. in Stomaphis graffii) to non-responsive species such as Cinara (Schizolachnus) pineti. The large interspecies variation of observed responses can be linked to other defensive mechanisms existing in the studied species, as well as to their mutualistic relationship with ants. The behaviour of shrinking is hypothesized to be the mutualistic response, developed from thanatosis, and being adapted to transportation by ant workers.Electronic supplementary materialThe online version of this article (10.1007/s10905-018-9662-4) contains supplementary material, which is available to authorized users.