Evimirus Karg, 1963

Halliday, R. B., 2010, Revision of the Australian Eviphididae (Acari: Mesostigmata) 2596, Zootaxa 2596 (1), pp. 1-60 : 12-13

Genus Evimirus Karg

Evimirus Karg, 1963: 270 . Type species Eviphis uropodinus Berlese, 1903: 243 , by original designation.

Diagnosis of genus. Palpgenu with six setae; femur II with two antero-lateral setae; sternal shield entire, well sclerotised, with three pairs of sternal setae; anterior margin of epistome with one prominent undivided point; dorsal shield highly arched, but not expanded onto ventrolateral margins of idiosoma, with 30 pairs of setae; peritrematal shields well developed, with post-stigmatal extensions expanded and elongated, tips reaching beyond level of posterior margin of epigynal shield; peritremes extending anteriorly beyond coxae I; intercoxal region of ventral idiosoma laterally compressed, sternal and epigynal shields anteriorly constricted; strips of skin between epigynal, peritrematal and anal shields very narrow; exopodal platelets II and III well developed.

Notes on the genus. The genus Evimirus Karg currently comprises eight species – E. breviscuti Karg & Schorlemmer 2009 ( Cuba) , E. convergens ( Berlese 1913) ( Indonesia, India, wrongly recorded from Italy by Bhattacharyya 1971), E. kargi Hirschmann 1975 (New Guinea), E. leptogenitalis Karg 1979 (South America), E. pentagonius Karg 1996 ( New Caledonia), E. pulcherpori Karg 1989 ( St. Lucia and USA), and E. uropodinus (Europe, USSR, USA) ( Karg 1989, 1996). Mašán & Halliday (2010) recently reported that Eviphis minimus Berlese 1920 (Java) is also a species of Evimirus . These species occur predominantly in tropical climates, with the exception of E. uropodinus , which has been found in moss, rotting wood, and glasshouses in Europe ( Berlese 1903; Castagnoli & Pegazzano 1985; Karg 1971). Walter (1999) and Walter & Meacham (2004) reported Evimirus in garden soils near Brisbane ( Saint Lucia) and in tropical rainforest soils in north Queensland. The species from Brisbane is now identified as E. uropodinus ( Berlese 1903) , and the species from north Queensland is here described as E. scutellatus sp. nov. Walter & Proctor (2001) reported that these species feed on nematodes.

The idiosoma of Evimirus is highly arched, almost hemispherical. Conventional slide mounting causes vertical compression that usually breaks and distorts the dorsal shield of these specimens. Most of the observations made here were therefore made from specimens in temporary lactic acid mounts in excavated slides. After examination, the specimens were returned to 70% ethanol for storage.

Some species of Evimirus have a pair of large and conspicuous pores near the outer margins of the peritrematal shield, posterior to the stigmata, approximately level with the posterior edge of coxa IV. The function of these so-called post-stigmatal pores is unknown, but they appear to have a secretory function. Figures 9 and 10 show scanning electron micrographs of two specimens of a species of Evimirus , one of which shows coiled streamers of a substance that has emerged from the post-stigmatal pores and apparently hardened on contact with alcohol. This substance can also be seen occasionally in slide-mounted specimens. The function of this substance is unknown, and it remains to be seen whether a similar phenomenon occurs in species that do not have large post-stigmatal pores, such as E. convergens and E. kargi .

The males of most species of Evimirus are unknown. Karg (1989) illustrated the ventral idiosoma and chelicera of E. uropodinus , and Karg (1996) briefly described the male of E. pentagonius . I here take the opportunity to describe the male of E. pentagonius in a little more detail, and illustrate it for the first time.

Figures

FIGURES 9–12. Evimirus spp. 9, Evimirus sp., female, ventral aspect, showing coiled strands of material extruded from post-stigmatal pores, scanning electron micrograph; 10, Evimirus sp., female, lateral habitus, scanning electron micrograph (photos by D.E. Walter and C. Meacham); 11, E. pentagonius, male, dorsal shield; 12, E. pentagonius, male, ventral idiosoma. Scale bar = 100 µm.