Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 77. (Budapest 1985)

Vásárhelyi, T.: Investigations on the allometric growth of Aradus species (Heteroptera, Aradidae)

Table 1. Growth ratio (r) and initial growth index (b) of allometric growth of body length, head length, pronotal width and length of antennái joints 2, 3 and 4, respectively compared to head width in 4 Aradus species. bimaculatus r b cinnamomeus r b corticalis r b ribauti r b body length head length pronotal width antennái joint 2 antennái joint 3 antenna! joint 4 1.49 5.37 0.91 0.81 1.66 1.86 2.23 1.10 1.58 0.55 0.59 0.66 1.40 4.57 1.17 0.98 1.19 1.45 1.58 0.31 1.34 0.24 0.76 0.30 1.22 5.13 1.08 0.93 1.36 1.74 1.77 0.52 1.38 0.32 0.66 0.37 1.45 5.37 1.09 1.02 1.37 0.48 1.27 0.30 0.66 0.39 Postembrional change of body length of four species {Aradus bimaculatus REUTER, 1872; A. cinnamomeus, A. corticalis and A. ribauti) compared to that of head width is shown on Fig. 1, showing considerable similarity (see also the data of Table 1). Data of adults of further 30 Aradus species (all three subgenera represented) are also figured by filled circles. The trends of the two coincide, thus, according to Matsuda (1962) the trend of postembrional growth in body length

—head width ratio is determined at generic level, consequently it may not play any great rôle in identification. On the other hand, both parameres could equally be used in allometric investigations. The ratio head length / head width The length of the head is similarly plotted against the width of the head for the same species with the same result as in the previous case (Fig. 2). The two measurements change isometrically (Table 1) if growth ratios are calculated from the L

2-adult data, however, in A. cinnamomeus, where L

1 larvae were also available, in this instar the clypeus is extremely short in connection with the undeveloped sucking apparatus thus the growth ratio seems to be high. When calculated from the second instar only, r = 0.99, b = 0.93. Here again the equal suitability of both head length and head width as reference measurement was obtained. Since the width of the head is easily measured and with relative accuracy in Aradidae, it is suggested to use this measurement for comparison of growth of other body parts. The ratio pronotal width / head width Pro-, meso- and metanotum of the first instar larva are on the whole equally developed. In later instars the pronotum develops more rapidly in comparison with the others, and it is especially expressed in its width since the lateral margin in this genus is flattened and widened. The same consideration applies to the allometric growth of the pronotal width and head width as in the previous cases (Fig. 3, Table 1). Worthy of mention are the four species at the rigth side of the diagram. Three belong to the subgenus Miraradus containing species with alate pronotum, but the fourth is Aradus (Aradus) bergrothianus KIRITSHENKO, 1913. A further species of the subgenus Miraradus (oervendetes VÁSÁRHELYI, 1980) is not separated (width of pronotum 2.6 mm, width of head 0.85 mm). In spite of certain tendencies, even the subgenera do not separate in this way.