OCR Text |
Show 588 MESSRS. BATESON AND BRINDLEY ON [Nov. 15, this, it is to be remembered that in most localities the high male is either unknown or very scarce, and it cannot be doubted that in these places the low males are really mature. Lastly, we know by the analogous case of horned beetles that high males coexist with low males, both being in this case of course mature. W e think, therefore, that we are justified in considering that the 583 males available for measurement were all adult. These specimens were laid out on squared millimetre paper covered with gum, and while the gum was still wet the posterior end of the forceps was brought up to one of the lines, and the length of the forceps was read to the nearest half millimetre, which is well within the limit of error. The results are set out in the accompanying curve (fig. 2), in which the figures on the ordinates denote Curve showing frequency of occurrence of forceps of various lengths in male Earwigs (F. auricularia). Ordinates give numbers of individuals; abscissae give length of forceps in m m . numbers of individuals, those on the abscissae denoting millimetres. The smallest length of forceps was 2'5 mm., and the greatest 9 m m. As the curve shows, the greatest frequency is grouped about 3*5 m m . and 7 mm. respectively. The mean form, having forceps of moderate length, 4-6 mm., is comparatively rare. W e consider that the number of cases is enough to justify the acceptance of these statistics, and it is unlikely that a greater number of cases would |