Amenia chrysame (Walker)

Colless, D. H., 1998, Morphometrics in the genus Amenia and revisionary notes on the Australian Ameniinae (Diptera: Calliphoridae), with the description of eight new species, Records of the Australian Museum 50 (1), pp. 85-123 : 93-95

Amenia chrysame (Walker)

Like the several preceding species, A. chrysame has a wide distribution in eastern Australia ( Fig. 10 ). To test whether it, too, might display significant geographic variation, a preliminary analysis was made of 6 measurements and 4 bristle characters on a small set of specimens. This suggested that frons-width (Frw, as defined above) does, indeed, vary geographically. The ratio FrwlPdc was therefore measured on 100 specimens, selected to cover the species' range. The ratio proved to have a highly significant regression on latitude (p<O. OI). However, a scatter-plot ( Fig. 11 ) shows that the regression reflects, not a regular c1ine, but an abrupt shift in average frons width at about 26 degrees south. Separate analyses of specimens from north and south of the 26th. parallel show no significant regression on latitude. However, the mean frons ratios were 0.27 and 0.20 respectively-a difference that, although small, is statistically highly significant (p<O.OI for t-test) .

On present evidence, I would interpret this as simple geographic variation; but the reason for its occurrence is not at all obvious. Perhaps it reflects some ancient physiographic discontinuity that has long since disappeared-indeed, perhaps the same one that gave rise to A. leonina and A. albomaculata . The matter is further discussed in Part 3.

Figure 11 shows several other interesting features: (a) a deficiency of specimens with relatively narrow frons in places between 28 and 31 degrees south; (b) an apparent surplus of such specimens in places between 26 and 28 degrees south-i.e., in the general vicinity of Brisbane; (c) a deficiency of specimens with relatively wide frons in places between 31 and 35 degrees south. If these represent more than fortuitous statistical fluctuations, I am at a loss to explain them.

(midline marked in degrees).

PART 2. FORMAL TAXONOMY

In this section I formalise the taxonomic decisions foreshadowed in the section on morphometrics and also describe several new species that have come to hand, together with new records and occasional notes on other species. "Specimens examined" are listed only for new species and diagnoses are left to be inferred from the keys. Original descriptions and synonymies are not cited, since they were more than adequately handled by Crosskey (1965, 1969, 1972) and have been recently collated by Kurahashi (1989).

Figures

Figure 10. Distributions of Amenia chrysame (circles), Amenia nigromaculata (triangles), and Amenia sexpunctata (squares) (overlapping records omitted).

Figure 11. Scatter-plot of 100 specimens of Amenia chrysame; axis I-FrwlPdc (see text); axis 2-latitude