THE DESERT 
165 
of Biskra, and collected in the dry valleys, locally termed Oueds, or 
Wadis. Here I saw Pyrameis cardui , four specimens of Colias edusa , 
and a single example of the neat little Mditaea didyma. On the 
earthy cliffs of the Oued the Tiger-beetle, Cicindela flexuosa , Eabr., 
and the Ant Myrmecocystus viaticus were hawking about, while the 
brilliant Chrysis ignita , Linn., was searching, I suppose, for nests of 
Eumenes. A Pimelia simplex was picked up from the ground and 
when killed exuded much fluid by the mouth. There were also found 
on the ground Adesmiafaremonti , and a female A. biskarensis } as well as 
the evil-smelling Bug Lygaeus fidvipes, Dallas, the last-named found 
by my daughter. The best collecting, however, was furnished by a 
large plant, almost a bush, of a species of Spergula. On or about 
its flowers were numbers of Bees, to wit: Colletes coriandri , in 
abundance; C. bmccatus, Per., two; G. acutus } Per., one; Andrena 
lepeletieri , a male; A. nigro-aenea, two; also two other male Andrenae, 
to which Mr. Saunders could not assign names; Osmia submicans , 
Mor., a male; Eucera algira , LepeL, a male; Podalirius atriceps, Per., 
and P. (?) ambiguus, one of each. Together with these was the Dipteron 
Catabomba albomaculata. There were also some very wary Wasps 
which I thought might be mimicked by this Syrphid, but I failed to 
secure any of them. 
It was at Biskra that I made my first acquaintance with the 
Desert, and was much impressed, as no naturalist can fail to be, with 
the severity of the struggle for existence thereon. To begin with, 
plants live under most adverse conditions, more especially as the 
prevailing lack of moisture is from time to time intensified by periods 
of exceptional drought. It was during such a period that I visited 
Biskra; as an obvious result of the drought extensive regions near 
the town, which gave evidence of having been cultivated in more 
favourable seasons, were then absolutely bare. My Bedawin assistant 
told me as we gazed over the desert from a lofty sandhill near the 
sulphur spring, that in ordinary years, where we then saw little save 
sand and stones, the prospect was “ all flowers.” Such vegetation as 
did meet the eye was much of it strange, often succulent, often pro¬ 
tected by thorns or spines, notably the Qedad or Camel-grass, a plant 
that no European mammal would attempt to eat. There was an 
Umbellifer with all the appearance of a Rush, another was possibly 
protected by its odour, but the milky-juice of the prevalent Euphorbia 
seemed to give it alone among plants an immunity from the attacks 
of camels and goats, though not from Deilephila. Perhaps the most 
showy plant on the desert was the parasitic Phdypaea violacea , Desf. 
(Probanchaceae)* 
