When Cockroaches Replace Ants in Trophobiosis: A New Major Life-Trait Pattern of Hemiptera Planthoppers Behaviour Disclosed When Synthesizing Photographic Data

Abstract

The mutualistic interspecific relationships of trophobiosis between trophobiont planthoppers (Hemiptera, Fulgoromorpha) providing food to the host called xenobiont, are reviewed. The degree of interspecific relationships between these symbionts varies from occasional or short time duration (a few hours to a few days) to longer ones, with trophobionts left free to escape (optobiotic type) by the xenobiont, or maintained enclosed in nests or ant shelters (cryptobiotic type). Of 267 collected cases, 126 are new illustrated observations. Occasional trophobiosis is documented in 13 families of planthoppers and appears to be quite general in Fulgoromorpha, although it is reported for the first time for Dictyopharidae, Eurybrachidae, and Nogodinidae. Xenobionts associated with planthoppers are reported from ants and other Hymenoptera, Lepidoptera, and Blattodea, but also from Mollusca and even small gekkonid vertebrates. Tettigometridae appear to be exclusively tended by ants, while Fulgoridae significantly more often by cockroaches (40%) than by ants (27%). Long-time trophobiosis occurs always with ants, cryptobiotic ones reported in Cixiidae, Delphacidae, Tettigometridae, Meenoplidae, Flatidae and Hypochthonellidae, while optobiotic ones remain restricted to tettigometrids. A particular focus on Tettigometridae attended by ants is provided with new etho-ecological observations of 92 currently described tettigometrids species, 32 different species (35%) are now known to be able to be ant-attended. In Bulgaria, where fourteen species occur, trophobiosis occurs with at least five species of them (36%). In tettigometrids, subsociality, sessility, and underground life appear to be key factors allowing more complex relationships with ants. However, the planthopper size and thus the amount of food (drops of honeydew) is probably also an important factor. This might explain many new observations in large-sized and often isolated fulgorids with cockroaches. Tapping of trophobiont forewings by cockroaches, moths, or of the bark subtrate by geckos has been observed, but antennal palpation behaviours by ants are the most commonly observed with tettigometrids, although not with larger planthoppers. In tettigometrids, specific tegumentary glands secretions (allomones) of the abdomen pleurites might also mediate their long-term mutualistic associations, even possibly completing honeydew kairomones actions mediating planthopper trophobiosis in general.