NOTES ON A TRIP TO THE SIERRA DE LA DEMANDA AND MONCAYO. 125 



The iioi'th slope of this long ridge was covered by dense beech forest, 

 up to a short distance from the rounded top. But for this short 

 distance there was a grassy slope, with only a few scattered trees 

 between the open top above and the dense forest below. This strip 

 was narrow, often less than 100 yards across (N. to S.), but extended 

 for several miles from east to west. This little strip occasionally pre- 

 sented half-a-dozen Erebias on the wing at once, and was prolific in 

 other things. It was here that the black larva of Arf/i/nnia aglaia was 

 most frequently seen. Several common Pyralids flew freely. Here, 

 too, occurred Pt/rausta albnrividalif; (if it be that), a species new to 

 western Europe, was fairly frequent, but very difficult to see, and 

 still more to catch, flying in the hot sun, twinkling amongst the 

 taller herbage, and disappearing mstantly if disturbed, so that to 

 follow up and catch a specimen was really difficult. We met with 

 it also on the hill on the other side from Canales, right out on the 

 open hill-top above the thickets of heath ; the weather was not 

 propitious, and only one was captured at this locality. 



When we met with the Erebias here on July 3rd, E. erias was 

 seen freely, but only one or two E. f^ti/f/ue occurred. The following- 

 day E. styf/ne was seen more freely, generally in very fresh condition, 

 the E. eviafi being in most cases somewhat worn. The interest of 

 these two species is, in their occurring together, but not merely so. 

 In occurring together each species has varied so far as to resemble 

 the other in size, general facies and arrangement of spots, to a degree 

 that no two races from any other part of Europe, so far as I 

 know, would do, though no doubt individual specimens from many 

 localities might be got that quite match them. Some Basses-Alpes 

 E. stynne are not very different from these. The K. aUjiine. in 

 approaching A\ evias, are larger than most European specimens (if I 

 may say European as distinguished from Spanish), and are much 

 darker beneath. They do not attempt to approach E. evias by 

 developing the third apical spot, differing in this from the form 

 bejarensis taken last year, in which the tendency is to a good 

 development of this spot. In the matter of this apical spot (or eye) 

 the movement is left to E. evias : in European specimens this eye is 

 usually well-developed, generally, indeed, of nearly, if not quite, the 

 same size of the other two. In these Spanish ones the apical eye 

 is much reduced in all except a few specimens, and in rare instances 

 is absent. The size of these E. erian is much the same as that of the 

 Fl. .^tjnive : indeed, it averages rather smaller, instead of much larger, 

 as is the European rule. There is also the curious fact that a few 

 specimens are smaller, with the rusty patches yellower and narrowed 

 downwards, the eye spots being diminished, so that there is a very 

 appreciable approach in general facies to Erehia zapateri, a Spanish 

 species occurring about 100 miles further south than these specimens 

 came from. I do not know that the two species ever occur on the 

 same ground, but if they do E. zapateri appears at least a month later. 



These may be taken to be the (for the present) extreme forms to 

 which Spanish E. evias is tending to vary. Why does ijt do so ? As a 

 rule, Spanish forms are larger than European. In E. evias they are 

 smaller, they are also paler, with which tendency these E. evias con- 

 form. The small £". styyne are larger than European types, and culminate 

 in the very fine form bejarensis, Avhich it is at first difficult to believe is 



