1894.1 99 



with rain and snow on the mountains northwards, was at Biskra suc- 

 ceeded by breezes and wind from the opposite quarters, with a rise of 

 temperature. At the same time P. cardui (which hitherto had not 

 been commoner during the winter than tortoise-shells in England are 

 apt to be in early spring) increased rapidly in numbers daily, until the 

 butterflies became as plentiful as Grarden "Whites in June over a 

 cabbage plot, or Meadow Browns in a well-stocked hay field. A 

 certain proportion of the increase in their population was undoubtedly 

 due to some bred in the vicinage emerging from pupse ; because there 

 were specimens to be seen, bright coloured and in prime condition 

 amongst the faded and worn, and a cripple was noticed one day with 

 wings not fully expanded. But the greater number must have 

 wandered hither with the wind from southern districts, to loiter in the 

 welcome shelter of hill sides and hollow^s. They soon made themselves 

 quite at home. 



It was natural to wonder what so many butterflies would find 

 about Biskra to lay their eggs upon. The plants selected by them 

 varied with the locality. Near the town, or (to be exact) near the 

 railway and Fort St. Germain, mallows were in favour. Strips of 

 Malva parviflora, L., on open ground, were thronged for several days 

 with egg layers, until some leaves were studded with from three to 

 six eggs apiece. A few plants of M. syJvestris, L., attracted less at- 

 tention, but yet were not entirely passed over. But all this in large 

 measure proved in the end to be " love's labour lost ;" when the eggs 

 were beginning to hatch out, the mallows were fed off by goats. Away 

 from the oasis, on the stony hills and wastes, oviposition took place 

 almost exclusively upon two species of inconspicuous plants, Fllago 

 spathulata, Presl , and Plantago ovata, Forskall, Each butterfly 

 seemed to lay only upon one kind of these plants, not upon both 

 indiscriminately ; and so where Plantago predominated and was at- 

 tracting the attention of most of the egg layers, a single butterfly 

 might be observed searching out chance Filago plants, and laying only 

 upon them. This was noticed in more than one place between Biskra 

 and Hammam-es-Salahin, otherwise Fontaine Chaude. The only 

 thistle met with in that neighbourhood, a miserable plant of Garduus 

 pycnocephalus, L., w^as, however, found to have on it a single egg. 



"Within the last week P. cardui seems to have diminished in 

 numbers (although still very common), perhaps through dispersion 

 over the district, or perhaps through emigration. 



IJiskra: April Uth, 1891. 



