Collembola and Thysanura of the Edinburgh District 249 



to us, in the form of its feet and mucro.^ Both claws of the 

 front feet are without teeth; the upper claws of the second 

 and third feet are sometimes, and the lower ones usually, 

 toothed. The colour is bluish olive-grey, some examples 

 being considerably paler than others ; none, however, are so 

 yellow-olive as olivacea on the one hand, or so violet-black 

 as violacea on the other. Dr Schott, to whom we have also 

 sent specimens of this Spring- tail, indeed considers it prob- 

 ably a pale variety of /. violacea, Tullb. (in lit. 1/5/99), and 

 it will be seen that his figures (15) of the foot-claws and 

 the mucro agree closely with those of our insect (Figs. 24, 

 25). But Prof. Eeuter, who has likewise seen some of our 

 specimens, considers them more nearly related to /. olivacea 

 than to /. violacea. " Sie sind," he writes, " was ich in Coll. 

 Fenn. als /. olivacea var. bestimmt habe." According to Dr 

 Schaffer, the post-antennal organ of /. grisescens (Fig. 23) is 

 relatively longer and narrower than that of /. violacea, and 

 like that of /. olivacea. It is possible that further research 

 will force us to consider all three forms as varieties of a 

 single species. 



Local data. — Ravelrig, several among dead leaves, 16th Oct. 1896 ; Flot- 

 terston, near Penicuik, a few among moss, 20tli Oct.; Swanston "Wood, 

 several in moss, 28th Oct. ; Hallyards, near Eatho, half a dozen under moist 

 bark on remains of old tree, 10th March 1898 ; Dalhousie, a good many under 

 bark, 19th March; Mortonhal], on fallen boughs, a few, Dec, and again in 

 March 1899, common among leaves ; Craigentinny Meadows, under pieces of 

 wood, common, Feb. ; Bush, near Rosslyn, March ; near Midcalder, May. 



Isotoma sensibilis, Tullb. 



Isotoma denticulcda, Schaffer (13), and (?) /. duhia, Renter (11). 



[Plate V. Fig. 5 ; Plate VII. Figs 26, 27.] 



Specimens of a small purplish Isotoma collected at many 

 localities around Edinburgh belong, according to Drs Schott 

 and Eeuter (who have kindly examined some of them), to this 

 species. Our Scotch examples have, like typical /. sensibilis, 

 two tenent hairs on each front foot, and three on each inter- 

 mediate and hind foot. The lower claw in our specimens 



1 Dr Schaffer points out to us that, owing to a mistake on the part of the 

 engraver, the mucro of his insect is figured (13) with a tooth too few. 



