38 BRITISH BUTTERFLIES. 



ment of " forwards " or " laggards " takes place, but, throughout 

 southern and central Europe, a more or less ill-developed partial 

 second-brood of Papilio machaon takes place, much more numerous, 

 however, in the low levels of southern Europe; the percentage of second- 

 brood examples in England is certainly very small. Floersheim (Ent. 

 Rec, xxi., p. 15) puts it at from one to two per cent, only, increasing 

 to as many as five per cent, in warm summers, but he states that it is 

 not always the most rapid-feeding larvae that produce second-brood 

 examples, the pupae that do so are certainly among the early-formed 

 ones, but not, in all cases, the very earliest ; indeed, in 1908, out of 

 the twelve pupae first formed, only two produced second-brood imagines, 

 in spite of their being subjected to a forcing heat in a vinery for more 

 than three weeks ; the others lived, but obstinately refused to be 

 forced, whilst others, which had pupated a week later, gave rise to 

 second-brood imagines under natural conditions, so that, though all 

 larvae which produce second-brood imagines feed up rapidly, many of 

 those which feed up rapidly do not disclose a second-brood. Another 

 point indicated, was that, among the larvae themselves, there is a great 

 variety in the time taken to feed up, the last larvae resulting from ova 

 laid during the first part of July, not pupating for fully ten weeks, 

 whilst the bulk, although taking longer to feed up than the very 

 quickest ones, did not take more than two-thirds of the time spent by 

 the slowest. A similar habit was recorded (Ent. Bee, xxi., p. 147) by 

 the same observer with regard to Laertias philenor, about ten per cent, 

 going forward to a second-brood, but, like Papilio machaon, it was not 

 the very fastest-feeding larvae that produced imagines the same 

 year, although those that did so were among the fastest, but the 

 " laggards " always go over the winter as pupae. In this species, too, 

 the percentage also appears to vary in accordance with the season, the 

 intensity of the sun, Floersheim thinks, being the chief factor. But, 

 in its native home, this Nearctic species produces "forwards" regularly, 

 apparently in proportion to latitude ; in the southern States, 

 whole broods go forward, and the species is reported as continuously- 

 brooded from "early spring to frosts;" farther north it becomes 

 triple-, and then double-brooded, but it is essentially a southern species, 

 with a tendency to dispersal, and, in the most northern localities it 

 reaches, its habits appear to be on all fours with those of Colias edusa 

 with us. Not unlike this species in its habits is the largest of the 

 Nearctic Papilionids, Heracliden cresphontes, an interloper from the 

 tropics according to Scudder, which, similarly, appears to be continu- 

 ously-brooded in the southern States with, at least, four practically com- 

 plete broods in Florida, but with the number of " forwards " rapidly 

 decreasing till it is only partially double-brooded in its more northern 

 limits ; the evidence seems to show that this species also has no 

 permanent standing in these districts, and the larval habits as described 

 by Seagrave at Cambridge, Mass. (Scudder's Butts. New England, ii., 

 p. 1313) also remind one much of those of Colias edusa in central and 

 northern Europe. Somewhat similar are the larval habits of Papilio 

 poll/. rene*, another southern species that spreads into more temperate 

 regions, which isalmost continuously-brooded in the West Indies and the 

 southern States, but, as it goes further and further north, the 

 number of " forwards " becomes fewer, until, in the more northern 

 parts of its range, it is only partially double-brooded, having lost to a 



