Atypical tRNAs are functional minimal tRNAs, lacking either the D- or T-arm. They are significantly shorter than typical cloverleaf tRNAs. Widespread occurrence of atypical tRNAs was first demonstrated for secernentean nematodes and later in various arachnids. Evidence started to accumulate that tRNAs of certain acariform mites are even shorter than the minimal tRNAs of nematodes, raising the possibility that tRNAs lacking both D- and T-arms might exist in these organisms. The presence of cloverleaf tRNAs in acariform mites, particularly in the house dust mite genus Dermatophagoides, is still disputed.

In collections of ectoparasites from 368 small ground finches, Geospiza fuliginosa, in populations from the islands of Isabela, Santa Cruz, San Cristóbal, and Santa Fé, in the Galápagos Archipelago, Ecuador, we found 8 species of mites. Four mite species were common on all islands sampled, i.e., Mesalgoides geospizae Mironov and Pérez (Psoroptoididae), Xolalges palmai Mironov and Pérez (Xolalgidae), and 2 new species, Trouessartia geospiza n. sp. (Trouessartiidae) and Proctophyllodes darwini n. sp. (Proctophyllodidae). Four other species were represented by single collections from G. fuliginosa, i.e., Pterodectes atyeoi n. sp. (Proctophyllodidae), Strelkoviacarus sp. (Analgidae), Dermoglyphus sp. (Dermoglyphidae), and Dermanyssus sp. (Dermanyssidae). Authorship of new species names is attributed to the 3 authors who prepared the descriptions (B.M.O.C., J.F., D.L.). Trouessartia geospiza and P. atyeoi were also found on previously collected specimens of other Geospiza species in museum collections. For the 4 common species, we found no differences in prevalence among the 4 island populations, but infection prevalence differed among the 4 species. The mean infection prevalence was high for T. geospizae (89%), moderate for M. geospizae (58%) and X. palmai (44%), and low for P. darwini (26%) in all populations. The feather mite fauna of G. fuliginosa was similar to that of other Geospiza species, and generally related to communities found on other emberizid finches.

Dermanyssina is a speciose and ecologically diverse cohort of mesostigmatid mites. Primitive dermanyssoid mites are free-living predators in soil and litter, but the more diverse members of the group form facultative and obligate parasitic associations with a variety of vertebrate and arthropod taxa. This study uses molecular sequence data from the 18S and 28S gene regions of the nuclear ribosomal DNA array in an attempt to test dermanyssoid monophyly and establish phylogenetic relationships between Dermanyssoidea and the other dermanyssine superfamilies. Results from the phylogenetic analyses suggest that the families Spinturnicidae and Spelaeorhynchidae are both more closely related to Eviphidoidea than to other dermanyssoid mites and that Dermanyssoidea as currently defined is paraphyletic. The analyses also indicate that Eviphidoidea is sister to Dermanyssoidea and should be used as an outgroup for future phylogenetic studies of Dermanyssoidea.

Two new species of tarsonemid mites, Excelsotarsonemus kimhansenae and E. mariposa are described and illustrated. Both species were collected from the canopy of lowland forest trees in Costa Rica. Dos nuevas especies de acaros tarsonemidos, Excelsotarsonemus kimhansenae y E. mariposa, son descritos e ilustrados. Ambas especies fueron recolectadas de copas de arboles de las tierras bajas de Costa Rica.