SCIENCE-GOSSIP. 



165 



SiREX juvENCUS IN SURREY. — I found a line 

 female of this insect in a garden at Leatherhead on 

 September 20th, this year. Can anyone tell me if 

 the male of this handsome fly is ever seen, I know 

 of no record of its capture ?— H. Mead Briggs, St. 

 Mary's Road, Ealing. 



Vanessa antiopa in Skye. — A friend who has 

 just returned from the Isle of Skye has given me a 

 fine specimen of the Camberwell Beauty butterfly, 

 which he took there on September 17th. Is not 

 this unusually far north for it to occur ? — K. A . 

 Dcaliin, Cofton Parsonage. 



Derivation of " Cleat." — I should be glad if 

 some one of your readers would supply me with 

 the etymology of the substantive, " cleat." I have 

 not heard of the word in the Midlands, but in 

 certain districts in Yorkshire it is in frequent 

 use. It is there applied to the colt's- foot {Tussilago 

 farfara). Near here (Bedford) is a hill which 

 is known locally as Cleat Hill. Upon this rising 

 ground is a thick deposit of clay, which renders 

 the soil eminently suitable for the prolific growth 

 of colt's-foot. Of that particular plant there 

 is a sufticiently large quantity to make it notice- 

 able. In the absence of any other reason for 

 the hill to be so named, I have supposed that 

 this distinctive presence of cleat is connected with 

 the origin of the particular appellation. — L.Amb. 

 Roberts, ig, High Street, Bedford. 



Unio littoralis in Pleistocene Time. — The 

 interesting article b}^ Mr. A. S. Kennard in the last 

 number of Science-Gossip is most valuable to all 

 students of the Mollusca, giving, as it does, a 

 reliable and up-to-date account of the distribution 

 in England of Unio littoralis, Lam., during pleis- 

 tocene time. Looking at the localities mentioned, 

 it would appear that they were situated in the line 

 of the ancient river system, and by this means this 

 sp ecies with other freshwater forms were dis- 

 tributed. A study of its present distribution in 

 France, Spain and other localities mentioned, with 

 the conditions of existence, might afford some idea 

 as to its manner of life in England. My object, 

 however, in sending this note is to mention one 

 other locality for the above species, not recorded 

 by Mr. Kennard, viz., Orton Waterville, near 

 Peterborough, where it was associated with the 

 usual mammalian remains and the following 

 mollusca : Planorbis carinatus, Limnaa peregra, 

 Bythinia teutaculata, Valvata piscinalis, Ancylus 

 Jluviatilis, Pisidium amnicum and Helices. — A . Loydell, 

 19, Chaucer Road, Acton, W. 



Leaf Variation. — In discussing the subject of 

 leaf variation as determined by the influence of 

 the environment, we must carefully distinguish 

 between such as is caused by the plant "struggling " 

 to avoid a too excessive transpiration, and such 

 as is due to the struggle to adapt itself to more 

 favourable conditions of assimilation. For instance, 

 in the dandelion leaves figured at page 117 ante, 

 2so. I grows under conditions where there is no 

 necessity for any special struggle of any kind, 

 Tience the leaf normally develops, but it is thin, 



and its palisade tissue is not well expanded. In 

 figs. 2, 3 and 4, the external conditions are much more 

 favourable both for transpiration and for assimi- 

 lation, hence the total area of the leaf is contracted, 

 while at the same time its thickness is increased, and 

 its palisade tissue is much more developed. It is 

 not exactly correct to say, therefore, as Mr. Wheldon 

 does, that plants "occupying the driest situations 

 exhibit the least development of parenchyma." The 

 thickness of the lamina must be taken into account, 

 and the ratio which the palisade bears to the 

 lacunar tissue is exceedingly important. In the 

 case of certain Ranunculi, Potamogeton, etc., which 

 grow partially immersed in the water. The action 

 of the aqueous medium by arresting the differentia- 

 tion of the leaves in the bud, tends to produce an 

 aphyllie more or less complete. Hence the process 

 here is an arrest of development, rather than a 

 special adaptation. As Mr. Wheldon puts it, 

 " the capillary leaves almost totally disappear, 

 and only leaves of the floating palmate or partite 

 kind develop." That is, in this case, while the 

 total area of the leaf is diminished, it at the same 

 time gets attenuated, transparent, and sometimes 

 the palisade tissue, etc., disappears altogether. — 

 {Dr.) P. Q. Keegan, Patterdale, Westmorland. 



Thecla pruni in Herefordshire. — In June of 

 the present year, I was out for a long day's tramp 

 with a friend in Herefordshire. Pond-hunting, for 

 which we were provided with the necessary impedi- 

 menta, was to be a subsidiary object of the day's 

 programme, and during our walk my friend pointed 

 out some iris and other aquatic plants that indi- 

 cated the presence of water. On reaching the 

 spot we found that the plants were growing 

 luxuriantly from the dried-up bed of a small pond. 

 Although all water had disappeared, the bed of the 

 pond was still sufficiently damp to easily take the 

 impress of one's feet, and I noticed that the bases 

 of the water-plants were thickly populated by 

 the molluscous inhabitants of the pond who had 

 migrated thither on the complete evaporation of 

 the water. But what attracted my attention most 

 was the profusion of a lepidopterous insect that 

 from limited entomological knowledge I could only 

 identify as one of the Hair-streaks. Having no 

 means of collecting any, I tcok two in one of my 

 pond-life bottles just for the purpose of identifica- 

 tion, and on consulting a very old and imperfect 

 entomological work some weeks afterwards I made 

 out the insect to be the black Hair-streak butterfly 

 [Thecla pruni) and found it described as very local, 

 and giving about half-a-dozen English localities. 

 On this I communicated with two friends who are 

 capable entomologists, and their replies coincided 

 in describing it as a very good find, neither of 

 them possessing a specimen. The insect was in 

 considerable profusion, quite a couple of dozen 

 flitting about the area of the dried-up pond, and 

 frequently resting on the aquatic plants, for the 

 day was rather a boisterous one. They were in 

 verj^ fine condition. The particular neighbourhood 

 of this small pond seemed especially attractive to 

 many and varied kinds of life. Odonata were 

 represented by one or two species, moths by several 

 species, and dipterous insects in profusion ; but 

 beyond the presence of the wild mint, which 

 certainly scented the surrounding air very strongly, 

 I could discern nothing that seemed likely to oflfer 

 special attractions to the insect tribe. I have 

 purposely refrained from giving the precise locality 

 of the insect, as it is not desirable for some 

 collectors to know this. — George T. Harris, 33, 

 Lindore Road, New \Vands'j.':rtJi, S.W. 



