FEEDING-BEHAVIOR AND PHYLOGENY - OBSERVATIONS ON EARLY DERIVATIVE ACARI

Based on laboratory observations of three species of Allothyrus (Paras itiformes: Holothyrida: Allothyridae) from south east Queensland and g ut content analysis of 62 individuals representing 11 species of Allot hyrus from eastern Australia, we determined that Australian Allothyrid ae are scavengers that ingest fluids only. Living arthropods, nematode s, snails and annelids were ignored, but dead arthropods were readily fed upon and were sufficient to maintain adults and nymphs for many mo nths. The adults were sluggish, timid animals that relied on armour, t hanatosis and probably on noxious chemicals for protection: the juveni les produced secretions from idiosomal glands. In contrast, most early derivative Mesostigmata that we tested (Sejina, species of Sejus and Uropodella; Uropodina, Polyaspis sp. and Cercomegistina, an undescribe d Asternoseiidae) were aggressive predators of small invertebrates and ingested fluids only; however, two species of Asternolaelaps (Sejina) had solid fungal and animal material in their guts. Similarly, the ea rly derivative acariform (Palaeosomata, species of Stomacarus and Loft acarus) and opilioacariform mites (an undescribed Opilioacarida from A ustralia) that we examined all ingested particulate foods, including f ungal and animal material. These observations are consistent with the hypothesis that the earliest mites were scavengers and opportunistic p redators that ingested solid foods and that fluid feeding is a derived condition linking the three orders of Parasitiformes (Holothyrida, Ix odida and Mesostigmata). (C) 1998 Chapman & Hall Ltd.