THE VARIOUS MODES OE EMERGENCE. 



69 



therefore it is an error to call fourth and even fifth brood, as has been 

 too often done hitherto, the autumnal individuals of some species, and 

 to re-commence counting their contemporaries of the spring as first 

 brood of the following year ; because for this computation to be correct it 

 would be necessary for the autumnal individuals to reproduce, and that 

 their descendants constituted the vernal brood ; this, indeed, may 

 happen in very favourable localities and seasons in the case of a very 

 small number of individuals of a few species, and we can speak in that 

 case of a fourth "extraordinary " brood, but these are very rare cases, 

 and one may remark that the earliest autumn individuals often belong 

 to one sex only, the male ; during the winter a few individuals of 

 Colias croceiis,'''^ Fourc, of Pararge megera, L., of Rinuicia pJdaeas, 

 L., and, though more rarely, of Coenonympha pamphilus, L., are always 

 ready to emerge from the chrysalis when a few warm days interrupt 

 the cold ; thus, in 1916, we collected individuals emerged only a few 

 hours before, in the Plan di Mugnone, m the first and again in the last 

 days of November ; in 1918, in a period of early and of late frost, with 

 very mild days between, we found several on the 25th and 30th of 

 January and 8rd of February. Also of Polyoimnatus icartis, and of A. 

 thetis, I have observed the emergence in favourable years of a small 

 number of individuals of both sexes in October, which showed the 

 features of the first generation, and were evidently precocious autumnal 

 individuals of the latter. We can add that in the case of Go7iepteryx 

 rhavini, L., and, in a less degree, in that of G. cleopatra, L., the emer- 

 gence in autumn of a certain number of individuals, mostly, if not 

 exclusively, of the male sex, which hybernate in the imago stage, a,nd 

 the emergence in spring of the rest of their brood is a constant fact. 



We must therefore give up the notion of a fourth, and still more of 

 a fifth brood, which too often figure in entomological literature, and 

 say: " autumnal precocious individuals of the first brood." This ex- 

 pression may at first sight appear contradictory, but if one reflects that 

 the reproduction occurs only in spring, it seems to me sufficiently 

 justified. 



By the name " apparent generation " one might designate in a 

 generic manner those groups of individuals or families which emerge 

 at a distance in time from their contemporaries owing to the " pauses" 

 or other reasons, and might by superficial observation be considered a 

 brood by themselves. 



Bearing in mind the preceding observations, and therefore guard- 

 ing against errors of interpretation in the examination of the data we 

 possess, it will prove easy to group the species according to whether 

 they produce one, two, or three " ordinary " broods (we shall see further 

 on the significance of this word), in climatic, geographical and annual 

 conditions most favourable to the development of the greatest number 

 of the said broods. 



We may take note : — 



(1) In the case of a single brood the condition of perfect insect is 

 reached at different periods of the year, according to the species. 



(2) In the case of two broods the first always emerges in the second 

 half of spring, and the second in August or, more rarely, at the begin- 



» edusa.—H.T.T. 

 / 



