OCR Text |
Show 1905.] IN THE BEETLE GONIOCTENA VARIABILIS. 529 The case is of peculiar interest not only on account of the great variability in a single species, but especially because of the rather close correlation between the two chief colour-types and the two sexes. Bateson found that on the hills behind the Alhambra at Granada 80 per cent, of the males were spotted and dark below, and over 70 per cent, of the females unspotted and light. In the Darro valley, perhaps a couple of miles away, only 62 per cent, of the males were dark, and 85 per cent, of the females were light; i. e. there was a much higher proportion of light specimens in each sex. On the other hand, at Castillejo, near Toledo, rather early in the season, of 75 specimens all were dark and spotted, all but one being males. There wras therefore some indication that the proportions vary with the locality, or possibly with the season; and it seemed important to determine whether the correlation between variation and sex was a genuine and permanent phenomenon, or was more or less accidental, depending on the local and seasonal conditions at Granada. 1 therefore took the oppoi'tunity, during a visit to Southern Spain this spring (1905), of collecting Gonioctena in various localities, in the hope of settling this question. I found that Spartium retama, upon which the beetle lives, grew abundantly in most of the hilly uncultivated districts I visited, except in the neighbourhood of Gibraltar, where I imagine that the rainfall is too great, and in the desert to the east of the Sierra Nevada, which is almost wholly without vegetation. Almost everywhere where I found the Spartium I found also Gonioctena, but never saw it on any other plant. Where the beetles were abundant they were beaten into a net, but when they were scarce it was necessary to search carefully for them and catch each one separately. This probably leads to a slight excess of reds in my samples, since they are much more conspicuous ; but when this method was adopted the bushes were searched very thoroughly, and I believe that the error may safely be disregarded. On one occasion one method was used in a particular locality, and two days later the other was tried in the same place; and the difference in the proportions of red and greens was not more than about 3 per cent., which might easily have been due to chance in a comparatively small sample. I collected the beetles at Honda, Granada, and in two or three localities in the neighbourhood of Malaga ; those at Ronda were obtained on March 23-24, at Granada March 25 and 28, and collections were made at Malaga at the beginning of April and again towards the end of the month. It will be most convenient to describe the Granada collection first. On the hills behind the Alhambra, between the Genii and Darro valleys, Gonioctena was exceedingly abundant, and I collected altogether 1382 specimens, 978 males and 404 females (Table I.). In the distribution of the different varieties they agree remarkably closely with those obtained by Bateson ten years ago in the same place. Bateson |