Hemistephanus

Monophyly of Hemistephanus

The following apomorphies support Hemistephanus as a genus distinct from Megischus, contrary to the opinion of Townes² and Gauld¹¹.

1. Setae on M+Cu subapical to central, far from origin of vein 1M
2. Vein 2-1A reduced or absent
3. Vein 2r usually short, much smaller than 4Rs
4. Metabasitarsus with a row of short conical spines anteriorly
5. Apical carina on pronotum present, wide
6. Pre-annular area and ruga differentiated.

Apomorphies for Hemistephanus

Qualitative and Biometric Analysis

80 characters (15 biometric) were proposed as a new character-set for the group. A hierarchical list of biometrical ratios is presented on table 1.

Influence of Size and Sex on the Variation of Characters

Smaller specimens often have more distortion or masking of qualitative and biometric characters than larger ones. Thus, for a given species, an unusually small specimen is generally much less characteristic than a very large one.

The morphometric variation is considerably different for males and females. This can be more easily observed with the ratio Pnl/Hd, which has low taxonomic value for females, but is the most accurate for males (Table 1).

Table 1. Ten more important ratios, ranked in descending order of taxonomic importance, for females and males of Hemistephanus. Relative importance of ratio Pnl/Hd indicated by a pointer.
Females	Males
01. Ov/Pt	01. Pnl/Hd
02. Ov/Tt	02. io/oc
03. io/oo	03. Pnc/Pnl
04. Pnc/Pnl	04. io/io
05. io/oc	05. 2-1A/1Cu
06. btc/btw	06. Pt/Gs
07. 2-1A/1Cu	07. btc/btw
08. fl2/fl1	08. fl2/fl1
09. Pt/Gs	09. Pt/Ptw
10. Pnl/Hd	10. T4c/T4l

Species Classification

The dendrogram below proposes a classification for the species (overall similarity). The numbers correspond to the dichotomic numeration on the key to species (not shown here).

Classification of Hemistephanus species.

Geographical Distribution

The geographical distribution of the genus Hemistephanus is presented below. This genus does not occur in Australia, as previously suggested ^12,15,16.

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This page last updated: November 21, 1997.