362 Mr. J. J. Walker's notes on Lepidoptera 



These circumstances render the present list of the 

 nocturnal groups of Lepidoptera a mere fraction of what 

 may reasonably be supposed to exist in so varied a 

 district, though, among the butterflies and the day-flying 

 moths, I think but few have been overlooked. 



The great Eock itself, a huge wedge-shaped mass of 

 ancient grey limestone rising abruptly on all sides to a 

 height of little short of 1400 ft., is, on its northern and 

 eastern aspects, quite precipitous and inaccessible ; and 

 the steep and arid western and southern slopes, exposed 

 to the full force of the afternoon sunshine, and but 

 scantily covered, except in a few favoured spots, with 

 brushwood and herbage, do not hold out any great 

 promise to the entomologist, or to the naturalist gene- 

 rally. Nevertheless the flora, especially in the spring 

 months, is of singular beauty and interest. The 

 exhaustive * Flora Calpensis ' of Dr. Kelaart (London, 

 1846) enumerates no fewer than 452 species of flowering 

 plants (one or two of these, so far as Europe is con- 

 cerned, being peculiar to this little spot) as native to the 

 British territory, and to the narrow sandy isthmus 

 which joins the Rock to the mainland, up to the boundary 

 of the Spanish lines. Insects, too, are to be found in 

 considerable variety, and of the 63 species of butterflies 

 enumerated in these notes, 35 have been observed more 

 or less abundantly on the Rock itself. Of these, Melitcea 

 aurinia, var. Desfontainei, Godt., and Anosia plexij^pus, 

 L. (the latter represented by a solitary individual, which 

 had wandered hither, possibly, directly across the ocean 

 from its transatlantic home), have been observed by me 

 in this locality only, and this is also the single spot on 

 the European side of the Straits where I have seen 

 Charaxes Jasius, L. This last-named butterfly, how- 

 ever, will probably be found in the district not uncom- 

 monly, as its food-plant, Arbutus uiiedo, L., is said to 

 grow abundantly in the wooded ravines near Castellar 

 de la Prontera, 17 miles from Gibraltar, whence the 

 fruit is regularly brought to the Gibraltar market by the 

 country-people ; and I have also seen the shrub in the 

 woods behind Alge^iras, where several very interesting 

 plants as Rhododendron ponticum, L., the "insecti- 

 vorous" Drosoplujllum lusitanicum, and the noble fern 

 I)ichso)ii(( culcita, L. Heritier, have almost their sole 

 European station. 



