1904.] 215 



found such shrubs as Atriplex hnlimus. Lyeium europcoum, &c., and both 

 here and on the di'ier phiins many succulent plants occur in profusion, 

 Suceda, Snlnola, Zi/fj/oplti/llum, Arthrocnemon, and othei's. At Hauimam- 

 es-Salahin ("Baths of the Saints" Gal/ice " Fontaine Chaude ") a 

 magnificent hot spring su[)plies the baths which hold a high reputation 

 among the Arab population for the cure of all complaints, espe- 

 cially those to which they are most subject ; here Arundo phrafj mites 

 is undistinguishable, except by its larger size, from the European form 

 with which we are familiar, attaining a height of from ten to fifteen 

 feet where it follows the line of the heated water running froui the 

 spring above. 



The most conspicuous plant, and one which is found everywhere 

 on the flat, is Linion la strum riinjoninnum. Its purple flowers are a 

 feature in the landscape in the month of May, and one can scarcely 

 find a fair sized specimen on which the large round terminal galls of 

 Oecocecis guyoneUa, Gn., are not conspicuous. I have seen quite a 

 thousand on one large shrub, the old dry galls remaining after their 

 occupants have left them. Succulent plants, probably from their 

 special adaptation to the storage of moisture, were noticeably much 

 frequented by Lepidoptem. It must be extremely interesting to a 

 botanist to study the methods by which almost every desert plant 

 seems to strive for the same result, possessing in each instance some 

 peculiar means of defence against the prevalent drought, either in its 

 manner of collecting or conserving a sufiiciency of water. It may be 

 mentioned that in 190-3 there was not a single shower at Biskra or at 

 Hammam-es-yalahin during the time I spent there. Perhaps for this 

 reason larvae seem to r(;cognise the advantage of frequenting the 

 stems of their food-plants ; in the interior of the stem any larva 

 must necessarily find more protection from scorching sun rays, as well 

 as being nearer to the limited water supply. 



One finds here among the Micros an unusual proportion of gall- 

 makers. This habit is adopted by at least seven distinct genera : — 

 Phalonia, Oecocecis, Coleophora, and four new ones {Aiioecisis, Cecido- 

 phaga, Hypocccis, and Froactica). 



1 am able to record nine gall-making species in these genera, 

 without taking account of Amhlypalpis olivierella, Egt., the galls of 

 which I believe I also found on Tamarix, and two others not yet bred, 

 one on Gymnocarpon jruticosum, possibly an inquiline, and one on 

 Ilaloxy lo n art tenia t urn . 



Another remarkable preference is to be noticed. The leaves of 



