David E. Walter

Mesostigmatid mites (Acari: Mesostigmata) on rainforest tree trunks: arboreal specialists, but substrate generalists?

Predatory mites (Acari: Mesostigmata) on tree trunks without significant epiphytic growth in a subtropical rainforest in Eastern Australia were assessed for habitat specificity (i.e. whether they are tree trunk specialists or occupying other habitats) and the influence of host tree and bark structure on their abundance, species richness and species composition. The trunks of nine tree species from eight plant families representing smooth, intermediate and rough bark textures were sampled using a knockdown insecticide spray. In total, 12 species or morphospecies of Mesostigmata (excluding Uropodina sensu stricto) were collected, most of which are undescribed. Comparison with collections from other habitats indicates that epicorticolous Mesostigmata are mainly represented by suspended soil dwellers (six species), secondarily by generalists (four species) and a bark specialist (one species). A typical ground-dwelling species was also found but was represented only by a single individual. In terms of abundance, 50.5% of individuals were suspended soil dwellers, 40.7% bark specialists, and 8.3% generalists. Host species and bark roughness had no significant effect on abundance or species richness. Furthermore, there was no clear effect on species composition. The distribution of the most frequently encountered species suggests that most mesostigmatid mites living on bark use many or most rainforest tree species, independent of bark roughness. These findings support the hypothesis that some epicorticolous Mesostigmata use tree trunks as ‘highways’ for dispersing between habitat patches, while others use it as a permanent habitat.

Gaeolaelaps invictianus, a new and unusual species of hypoaspidine mite (Acari: Mesostigmata: Laelapidae) phoretic on the red imported fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae) in Louisiana, USA

ABSTRACT A new species of hypoaspidine laelapid mite, Gaeolaelaps invictianus, associated with the red imported fire ant Solenopsis invicta Buren in the southern United States of America is described. This new species is unusual among the gamasine Mesostigmata in lacking a postanal seta in adults of both sexes and among species of Gaeolaelaps in being phoretic on dispersing male and female alate ants, lacking dorsal shield setae z3 and J1, and in having a separate anal shield in the adult male. The chelicerae of this new species are similar to free-living forms, suggesting that it may be a predator of small invertebrates in the ant colony.

Phoretic Mite Associates of Mountain Pine Beetle at the Leading Edge of an Infestation in Northwestern Alberta, Canada

Abstract We identified species of mites phoretically associated with mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae), collected from bolts of lodgepole pine, Pinus contorta Douglas ex Louden (Pinaceae), and pheromone-baited traps in northwestern Alberta, Canada. Mite load and species composition were compared between beetle sexes and with beetle emergence time and estimated body size. The vast majority of mites associated with D. ponderosae in Alberta belonged to three species: Proctolaelaps subcorticalis Lindquist (Acari: Mesostigmata: Melicharidae), Histiogaster arborsignis Woodring (Acari: Astigmatina: Acaridae), and Tarsonemus ips Lindquist (Acari: Prostigmata: Tarsonemidae). There was no difference in mite loads on male and female beetles recovered from bolts in the laboratory and those from pheromone-baited traps in the field. More mites were found on larger beetles in the laboratory, but only T. ips showed this pattern on field-trapped beetles. There was no relationship between total mite load or load by mite species and beetle emergence time in the laboratory, but total mite load on field-trapped beetles decreased over the collecting season (10 June – 3 September 2009) at five collection locations (Grovedale, Blueberry Mountain, Hythe, Evergreen Park, and Glenleslie). This study is the first to document the assemblage of phoretic mites on D. ponderosae in Alberta and will help to direct future research on their interactions.

Mites (Arachnida: Acari) inhabiting coffee domatia: A short review and recent findings from Costa Rica

Abstract Eight previously unreported domatia-inhabiting mites are reported from Coffea arabica L. and C. eugenioides S. Moore (Rubiaceae) accessions planted in Costa Rica. One of these, an Asca sp., was found to be carrying fungal spores on its cuticle. A review of the literature on mites in coffee domatia is presented.

A new species of eriophyoid mite (Acari : Eriophyidae) on sugarcane in Australia

Abstract Seven species of eriophyoid mites (Acari: Eriophyoidea) are known to attack sugarcane plants (Saccharum spp., Poaceae) and related grasses in various parts of the world, but except for unconfirmed reports of Aceria sacchari and Abacarus sacchari, Australia had been thought to be free of these pests. Herein, Abacarus queenslandiensis n. sp. (Eriophyidae), vagrant on leaf surfaces of sugarcane in Australia, is described. Also, Cathetacarus n. gen. is erected for the distinctive mite, Catarhinus spontaneae Mohanasundaram, 1984. In addition, a key to the eriophyoid mites known to occur on sugarcane plants in the world is given.

From the subantarctic to the subtropics: a revision of the Davacaridae Kethley, 1977 (Acari: Trigynaspida: Mesostigmata) with the description of a new genus and three new species

The family Davacaridae is shown to consist of at least two genera (Davacarus Hunter, Acanthodavacarus n. gen.) and four species that are distributed from subantarctic islands (D. gressetti Hunter) to Tasmania (D. reginaldi n. sp.), and to mainland Australia (D. lindquisti n. sp., A. klompeni n. sp.) at least as far north as the subtropical rainforests of south-east Queensland. These mites share a number of striking synapomorphies including the paedomorphic retention of the deutonymphal pattern of sclerotized plates in the adult, a secondary thickening of the cuticle around those plates and a lateral cheliceral excrescence that adheres to the cheliceral teeth. Species of Davacarus have lost the pregenital shield, have an intricate endogynium and four pairs of large, sessile opisthosomal glands; species of Acanthodavacarus have a pregenital shield with a pair of setae and two pairs of hypertrophied opisthosomal glands on short horn-like protrusions.