Myrmozercon iainkayi Walter

Shaw, Matthew D. & Seeman, Owen D., 2009, Two new species of Myrmozercon (Acari: Laelapidae) from Australian ants (Hymenoptera: Formicidae), Zootaxa 2025, pp. 43-55 : 51-53

Myrmozercon iainkayi Walter

( Fig. 5 )

Material examined. One male, 1 female ex Polyrhachis (Cyrtomyrma) australis Mayr from a carton nest made of silked foliage in garden tree, Anstead, Brisbane 27º 32' 25" S, 152º 51' 26" E, J. Beard coll., 24 Feb 2008; 4 females from same nest, except 25 Mar 2008; 19 females, 7 males, 2 deutonymphs and 3 protonymphs from same nest except 8 April 2008. Specimens in QM, one female mite registered as QMS 83732.

Walter (2003) described the male and female stages of M. iainkayi . Nymphal stages are described below.

Protonymph (n=3)

Dorsum: Pale, poorly sclerotised, 495–520 x 400–480. Podonotum with ca. 35 setae, pygidial shield with ca. 24 setae. Anterior edge of pygidial shield abutting or approaching podonotal shield for no more than 12 µm at midline. Enlarged paired mesonotal scutella present laterally, entirely filling the gap between podonotal and pygidial shields ( Fig. 5 c). Each mesonotal scutellum with ca. 7 setae. Dorsal setae with minute distal barbules (too small to show on figure).

Ve n te r: Peritremes extremely short. Circum-anal setae thick and strongly barbed.

Gnathosoma: Dorsodistal edge of palp femur lacks a swelling or other structure. Cheliceral digits edentate; fixed digit slender and parallel-sided; movable digit broad at base with a weak apical hook. Deutosternum with 14–15 rows of denticles. Hypostomal setae and palp coxal seta barbed.

Legs: Chaetotaxy hypertrichous: coxae 6-4-4-1; genu IV 1, 2/0, 2/0, 1, seta pl positioned distally; femur I with an additional ventral seta (2, 4/3, 2); and femur III with an additional pd seta (1, 4/1, 0). Leg setae with minute distal barbules.

Deutonymph (n=2)

Dorsum: Pale, lightly sclerotised, 515–644 x 476–540. Podonotal region with about 43 setae, opisthonotal region with about 44 setae. Dorsal shield covering entire subcircular dorsum except small area of soft cuticle posteriorly. Setae with minute distal barbules.

Ve n te r: Sternal shield with reticulate ornamentation, bearing st1–3 and st5, st4 absent. Soft cuticle hypertrichous. Peritremes short as in adults; barely passing posterior edge of coxa III. Circum-anal setae strong and barbed.

Gnathosoma: Dorsodistal margin of palp femur bears a low swelling positioned internally of midline and directed anteriorly. Palp femur without dorsal condyle. Both cheliceral digits edentate; fixed digit slender and parallel-sided; movable digit with broad base and strong apical hook. Deutosternal groove with 12 closelyspaced rows of denticles.

Legs: Coxae 6-6-6-4. Trochanters 5-6-6-5. Leg I femur 2, 3/2, 2/2, 2, genu 2, 2/2, 2/2, 2, tibia 2, 2/1, 2/1, 2; Leg II femur 2, 2/2,2/1, 1, genu 2, 2/1, 2/1, 2, tibia 2, 1/1,2/1, 2; Leg III femur 1, 2/2, 2/2, 0, genu 2, 2/1, 2/ 1, 2, tibia 2, 1/1, 2/1, 2; Leg IV femur 1, 2/3, 1/2, 0; genu 2, 2/1, 2/1, 2, tibia 2, 1/1, 2/1, 2. Leg setae with sparse distal barbules. Tarsi are more strongly sclerotised than other leg segments.

Remarks. The leg setation of the protonymph of M. iainkayi is the same as for other gamasine protonymphs ( Evans 1963), with some exceptions. The strong hypertrichy on most coxae (6-4-4-1) is only slightly less extravagant than that found in later stases. Genu IV has a pl seta (1, 2/0, 2/0, 1). This pl setae is positioned distally as in most other laelapid protonymphs that have two pl setae as deutonymphs and adults. Femur I has an additional ventral seta (2, 4/3, 2) and femur III has an additional pd seta (1, 4/1, 0). The leg setae have minute distal barbules.

In the deutonymph, leg setal counts agree with those given for adult M. iainkayi by Walter (2003), including typical coxal setal counts of 6-6-6-4, but asymmetric variants include coxa II with only five setae, and coxa III and IV may both have an additional seta.

Initial collections of one male and five female specimens came from the propodeums of worker P. australis which ventured out to defend their arboreal nest. Each of these worker ants bore a single M. iainkayi . Later the whole nest was collected and placed in a shallow artificial enclosure with clear perspex sides. The majority of the ant colony did not survive the transfer to the artificial enclosure and remaining members were not able to rebuild their carton nest using larval silk because there was only one larva in the nest at the time of collection. A tally of all ants collected gave slightly more than 30 winged queens, 63 males and 61 workers. Total mite collections from this nest totalled 24 female, 8 male, 2 deutonymphs and 3 protonymphs of M. iainkayi . Many mites were not collected from ants but were collected from the surfaces inside the artificial enclosure. Mites collected directly from ants usually clung singly to the propodeum and did not show a preference for a particular caste. No M. iainkayi were observed to move unless prodded. Even when detached from their host and apparently healthy they remained quiescent. While on an ant the mites remained stationary. Most mites adopted a stereotyped posture at the rear of the propodeum with their gnathosoma facing towards the petiole. Some mites were observed in other positions on their hosts. One hour after placing the captured colony in the artificial enclosure, one healthy queen had a M. iainkayi riding on her head and one worker had three M. iainkayi on her propodeum. A total of three M. iainkayi were also observed on the wings of two moribund queens and another on the head of a moribund worker. The only other nest inhabitants observed were one unemerged, and a few empty, syrphid pupal cases.

This is the first fully identified host for this mite. Inquiries were made to the University of Queensland Insect Collection to locate host specimens for the original series of M. iainkayi but without success.

Figures

FIGURE 5. Myrmozercon iainkayi Walter: (a) deutonymph dorsum; (b) deutonymph venter; (c) protonymph dorsum; (d) protonymph venter. Scale bar = 100 μm