April I, 1879] 



NATURE 



507 



On the Pupation of the Nymphalidae 



In Nature, vol. xvi. p. 502, I called attention to some ob- 

 servations and experiments of mine on the pupation of several 

 species of Nymphalida: and Pieridce, the results of which were : 

 (l) That, in the species referred to, a connection (larvo-pupal 

 ligament) exists between the larva-skin and the chrysalis which 

 is the sole support of the suspensus chrysalis during the final 

 process of pupation, namely, during the extraction of its tail 

 from the larval skin and fastening the anal hooks in the sup- 

 porting silk ; (2) That this ligament is not confined to the 

 Suspensi, but exists also in species of the '^Succincti where it has 

 not the same function to perform ; and (3) That nevertheless, in 

 these latter cases, when other support is withdrawn by cutting 

 the girdle before pupation, this ligament is capable, in the ma- 

 jority of cases, of fulfilling the same office as it does in the 

 Suspensi. 



These views have recently received important confirmation and 

 extension at the hands of Mr. W. H. Edwards, of West Vir- 

 ginia. I refer in the first place to a paper of his in the Canadian 

 Entomologist for December, 1878, which is reprinted in the 

 Entomological Mo7tthly Magazine for the present month. Here 

 Mr. Edwards describes the ligament as found by him in Grapta 

 interrogationis and Danais archippus. In the latter it is black. 

 Of the former Mr. Edwards writes : '* When I lifted the flap of 

 skin entirely clear of the struggling segments, and cut it off a 

 little below the tail, the bendings and contortions were not inter- 

 rupted by my interference, nor was the effort to reach the silk in 

 the least abated. Held firm by the stretched ligament, which 

 was in plain view, the body rose, and the tail, which had got 

 well outside the padded skin and was, before complete extrica- 

 tion, bent backward, now bent forward, and by the upward 

 swing, was brought exactly to the silk. Several times as I was 

 lifting, the skin and chrysalis together were dislodged, and fell 

 into my hand. Then by drawing the skin back the ligament was 

 exposed, and it was distinctly seen that it was attached to the 

 chrysalis by the pointed ends of the ridges before mentioned 

 and that there was no other connection between skin and chrysa- 

 lis." As regards the second and third points mentioned above, 

 Mr. Edwards writes to me as follows: — "I experimented on 

 Papilio ajax and P. asterias, also following your illustration with 

 Pieris, and was successful in discovering the membrane in both 

 species. Ajax has the terminal part of the chrysalis remarkably 

 short, but although I cut the band and let the larva hang, the 

 chrysalis generally succeeded in reaching the button of silk. So 

 with Asterias, in which the terminal joint is longer. I have no 

 doubt all the Papilionidse possess this membrane, and probably 

 the Satyridse." 



We have now the existence of the ligament demonstrated in 

 three species of Suspensi, viz., V. urtica, G. interregationis, and 

 D. archippus ; and in three or four Succincti, namely, Pieris 

 brassica, Papilio ajax, and P. asterias, and probably also in A. 

 cardatnines ; all of which latter also pupate more or less success- 

 fully when artificially converted into suspensi by cutting the 

 loop. To the case of A. cardamines, which, when pupating as 

 an artificial suspensus, does not remove the tail of the chrysalis 

 from the pocket of the old larva skin, there is a parallel in 

 Pyrarga egeria, and perhaps also in Epinephele janira, in regard 

 to the former of which Mr. Newman states {"British Butter- 

 flies," p. 85): — "The skin of the caterpillar alw^ays remains 

 attached to the anal extremity [of the chrysalis], even after the 

 Ijutterfly has escaped." In reference to Janira he writes {op, 

 cit., p. 92) : — " Three of my specimens changed to chrysalids," 

 &c. ; "in two instances the skin of the caterpillar remained, 

 enveloping the anal extremity, so that the chrysalis could not be 

 suspended ; in the third it hung for a time from a blade of grass, 

 the skin still enveloping the anal extremity, but attached by its 

 anal hooks to silken threads on the grass." 



Mr. Edwards promises further researches during the coming 

 season, for which he has favourable opportunities in his locality, 

 and I think we may confidently look for interesting and perhaps 

 important results. The question of rank in the diurnal lepid- 

 optera is one that has been much contested (see Wallace's essay 

 on "The Malayan Papilionidse," &c., "Contributions to the 

 Theory of Natural Selection," p. 133), and will probably be de- 

 cided differently, according to the standard of perfection set up ; 

 but the question of da-ivation is probably more capable of definite 

 solution, and on this point the suspensory ligament seems well 

 calculated to afford important guidance. In the meantime more 

 extensive observations and experiments are wanted, and will no 



doubt be afforded by those interested in the subject when their 

 attention has been once directed to the matter. 



Milford, Letterkenny, March 26 J. A. Osborne 



Tides at Chepstow 



I AM unable to find any certain record of " exceptionally high 

 tides " at Chepstow. They must be of rarer occurrence than is 

 commonly supposed. A very high one is mentioned as having 

 flooded the lowest parts of the town January 29, 1846; and a 

 very low neap tide is noted in a wharfinger's books, on March 

 19, 1876. Measurements of these cannot be obtained ; but the 

 highest known rise of the tide at Chepstow since the erection of 

 the iron passenger bridge in 18 16, has not exceeded fifty feet; 

 and probably has never attained such an elevation even with the 

 conjunction of much fresh water inland, and a stiff S.S.W. 

 breeze. 



Fair proof of the accuracy of this statement is afforded in 

 the elevation of the railway bridge that spans the Wye about 

 two miles and a half from its mouth. By the requirements of 

 the Admiralty, a clear headway of fifty feet had to be left above 

 the highest known tide. Besides attention to these require- 

 ments, the contractors had to provide approaches to the roadway 

 of the bridge, involving, on the Gloucestershire side, a long and 

 deep cutting through limestone rock, and on the Monmouthshire 

 side a lofty embankment. A very large outlay of money 

 depended on the determination of the "highest known tide," for 

 it regulated the point of suspension for the bridge, and the level 

 of the approaches. Yet, as may be seen in the official report 

 appended to these v\otes, forty-fojir feet only were allowed for 

 the "rise of the tide." The readers of Nature may refer for 

 a drawing of the bridge, plans, and a detailed report, to the 

 Illustrated London News of July 24, 1852, to satisfy themselves. 



Through the kindness of Mr. Henry Gillam, and of Messrs, 

 Miller, the lessees of the salmon fisheries in the Severn and in 

 the Wye, I have received mea^urements of this day's tidal range 

 in both rivers, taken personally by those gentlemen. Amongst 

 well-known points I cite the height at Portskewitt landing stage. 

 New Pa>sage, on the Severn, 39 feet 3 inches ; at Chepstow 

 railway bridge, 39 feet ; at Chepstow Passenger bridge, about a 

 quarter of a mile higher up the river, 35 feet. 



In the geographical part of Knight's Cyclopredia, article 

 " Chepstow," the rise of water at Chepstow Bridge at high tide is 

 given as "fifty feet, being the greatest tidal rise in Europe." 



The highest reliable measurements that I have met with for 

 the tidal rise in the Severn are 47 feet 6 inches, marked on the 

 Portskewitt landing-stage. 



For accidental phenomena affecting the tidal levels, I refer to 

 the following extract from the Bristol Tide Book ; — 



By a careful comparison of the differences of the predicted and 

 observed heights of tide at Bristol with the contemporaneous 

 heights of the barometer, Mr. Bunt found that a depression of 

 one inch in the mercurial column is accom-panied by an elevation 

 of fourteen inches, nearly, in the height of the tide. Hence, by 

 observing the state of the barometer a few hours before high 

 water, we obtain the following correction of the height predicted 

 in the tide table : — 



When the barometer j 

 stands at 



Inches. 



28 6 



29 o 

 29 4 



29 8 



30 o 

 30 4 

 30 8 



Add to the 

 predicted height 



Deduct from the 

 predicted height 



Inches. 

 ( 20 



8 



3 



o 



6 



II 



Our highest tides for 1879 are marked in the table as occurring 

 Monday, March 10, and Tuesday, April 8. John Yeats 



Chepstow, March 24 



P.S. — Through the kindness of the four brothers Miller, I am 

 this morning in possession of measurements of yesterday's tide 

 in the Severn and Wye, taken, by the request of the firm, at 

 distant stations. I .nclose one, at Tintem Abbey, taken by 

 W^m. Bowen, a regular correspondent of the Meteorological De- 

 partment. 



March 25 



Tintem Abbey, near Chepstow, March 24 

 Mr. Alexander Miller 



Dear Sir, — As requested, I have taken the height of the flow 

 of tide this morning and find it 15 feet i inch above present level 



