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Variability of A. peregrinus
There is a wide variation in colour of A. peregrinus the majority of specimens are either light-brown or dark-brown, intermediate shades, however, occur. The light-form was probably the one originally described by Smith, in 1876, from Canterbury; the same author later (1878) described the dark-form from Otago as a different species, and in 1947 Cushman again described the dark-form from a unique male from Mt. Egmont, in the North Island of New Zealand, collected by the late R. J. Tillyard. A long series of specimens show a striking gradation of shades between the dark-brown and light-brown forms. In the case of the light-form the legs may be entirely light-brown, and in some individuals the darkening of the coxae, trochanters, and femora is very noticeable. The darkening of the stigma, thorax and antennae, is to some extent correlated with the darkening of the basal joints of the legs. There are two specimens in the Hudson Collection, at the Dominion Museum, with the basal ⅔ of hind femora black, also another specimen in the Dominion Museum Collections, from Dunedin with similarly coloured hind femora, but in all other respects they are similar to the typical form. The light and dark forms of A. peregrinus may eventually be correlated with seasonal, geographical distribution or host relationship of the species, but there is no useful purpose to be gained, in the present state of our knowledge of this species, to recognise sub-specific rank within the species.
The discoidella diverges from the nervellus either above, at, or below the middle. The following Table (No. 1) gives the relative occurrence of the position on the nervellus from which the discoidella diverges, in both the light and dark forms.
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| Nervellus broken at | Above Middle. | Middle. | Below Middle. |
|---|---|---|---|
| Dark form % | 25.0 | 37.5 | 37.5 |
| Light form | 41.7 | 50.0 | 8.3 |
From the above Table, it is seen, that in the majority of dark forms the nervellus is broken at or below the middle, while in the light form, it is broken at or above the middle, although in both forms the nervellus may be broken, above, at or below the middle.
The propodeal costulae (carinae) show considerable variation in degree of development. Some individuals show the costulae well developed and clearly marked, the areola entire, while in others the costulae and areola are virtually wanting, except that the lateral and posterior costulae, are usually present; in the majority of individuals the costulae are more or less indicated.
The post-petiole varies in shape from rectangular to 1 ½ times as long as its minimum width. The length/maximum breadth ratio of the post-petiole area shows gradations similar to that of other characters, ranging from 1.0 (as long as wide apically) to 2.16 (or over twice as long as wide apically). The average ratio for the specimens measured is 1.54, which is about 1 ½ times as long as its apical breadth. The post-petiole is usually wider at the apex than it is at the base, but in one individual in which the post-petiole is as long as wide apically, the basal width is equal to the width at apex.
The number of joints in the flagellum of the antennae varied from 52 to 58 in the dark form and from 53–56 in the light form. The relative length of the 1st and 2nd joints of the flagellum is given by the ratio 1st joint/2nd joint. The dark-brown form gave a ratio from 1.5 to 1.6, the light form from 1.2 to 1.5. In this case the 2nd flagellum joint in the dark form was relatively shorter in relation to the 1st joint, than in the light form.