Myiopharus dorsalis (Coquillett)

O’Hara, James E., 2007, A new species of Myiopharus Brauer and Bergenstamm (Diptera: Tachinidae) parasitic on adults of the sunflower beetle, Zygogramma exclamationis (Fabricius), Zootaxa 1521, pp. 31-41 : 33

Myiopharus dorsalis (Coquillett) species group

There are various external similarities and differences among Myiopharus species that will one day help in the division of the genus into species groups or subgenera. It is beyond the scope of this paper to explore the intrageneric relationships of Myiopharus species in such detail, but there are two small yet discrete groups of species that can be separated from the other species on the basis of modifications of the female terminalia ( Wood 1985). Females of most Myiopharus species have a simple tubular ovipositor that is a groundplan state of the Blondeliini and presumably Myiopharus as well. The female of the type species of Myiopharus , M. metopia , has this type of ovipositor. A few species of Myiopharus have an ovipositor that has been modified into a curved and pointed piercer, and these species are thought to form a monophyletic lineage, termed here the M. doryphorae (Riley) species group. This species group comprises M. americanus (Bigot) , M. doryphorae , and M. macellus (Reinhard) in America north of Mexico and includes at least several Neotropical species. A second group of Myiopharus species, here termed the M. dorsalis (Coquillett) species group, is characterized by a peculiar ovipositor in which sternite 7 is laterally flattened and apically rounded ( Figs. 7–8 ). This unusually-shaped ovipositor may be designed to slide under an elytron of an adult beetle during oviposition ( Wood 1985), thus ensuring a relatively safe delivery of a ready-to-hatch egg onto a host.

In addition to the specialized ovipositor, females of the M. dorsalis group possess a dense tuft of closely appressed setae on the katepisternum in front of and overlapping the mid coxae ( Fig. 6 ) that is apparently unique to this group. The setae comprising the tuft are unusual in that they are parallel-sided and somewhat blunt-tipped, rather than evenly tapered to a point like normal setae. The purpose of this peculiar tuft of setae is not known. It is not found in males of the M. dorsalis group, although males of M. neilli have a denser group of setae in this position than males of other members of the group and most other Myiopharus .

The M. dorsalis group is clearly monophyletic based on its specialized ovipositor and katepisternal tuft of setae in females, and comprises M. canadensis Reinhard ( Fig. 5 ), M. dorsalis , M. securis Reinhard , and new species M. neilli ( Figs. 1, 3 ) in the Nearctic Region. Other features shared by members of the M. dorsalis group but varied within the genus include: facial ridge setose on less than lower half ( Figs. 2, 4 ), 3 katepisternal setae (illustrated for M. dorsalis in Fig. 173 by Wood 1987), median discal setae on abdominal tergites 3– 4, and no male “sex patch” (sensu Wood 1985) on abdominal tergites 4 and/or 5.

Figures

FIGURES 7 – 11. Myiopharus neilli sp. nov. 7. Left lateral view of female ovipositor. Scale bar = 0.2 mm. 8. Posterior view of female ovipositor. Scale bar = 0.2 mm. 9. Puparium. Scale bar = 1.0 mm. 10. Posterior and slightly dorsal view of posterior spiracular discs of puparium. Scale bar = 0.2 mm. 11. Puparium within remains of host, Zygogramma exclamationis. Beetle is typically decapitated between prothorax and mesothorax. Scale bar = 1.0 mm.

FIGURES 1 – 6. 1. Myiopharus neilli sp. nov., left lateral view of male holotype. Body length = 6.9 mm. 2. M. neilli, oblique view of head of female allotype. Scale bar = 0.5 mm. 3. M. neilli, left lateral view of female allotype. Body length = 6.9 mm. 4. M. dorsalis, oblique view of female head. Scale bar = 0.5 mm. 5. M. canadensis, showing dark thorax and shiny frons that characterizes males of some Myiopharus species (image courtesy of S. A. Marshall). 6. M. neilli, ventral view of female showing tufts of setae on katepisternum in front of mid coxae. Scale bar = 0.3 mm.