240 THE BNTOMOLOGIST^S RECOliD. 



and July 1st (one of the $ s having very imperfect rings on the hind- 

 wings), and six others a few days later. Their ova began to hatch on 

 July 9th, and the larvae fed during the remainder of July, and pupated 

 during the first week of August. The first imago of these 8rd bro(;ds 

 appeared on August lOtb, and the last on August 19th. The 

 autumnal emergences formed 15 % of the pupa3, the majority are 

 passing the winter in the latter stage. All the insects were 5 s except 

 one, and were without the omicron on the fore-wings, also with one 

 exception. One was ab. hi-obsoleta, and in 14 the black ring on the 

 hind-wings was very imperfect, in several only just traceable. 



No generalisation can be made till the 3rd broods are complete by 

 emergences from the pupa as 1st broods of 1899, but it may be noted 

 that amongst the autumnal emergences there was only one reversion 

 to the $ grandparent, and this was an aberration in other respects 

 (1 in 32), and that all were $ s with the one exception. 



An experimental enquiry into the struggle for existence in 

 Aglais urticas. 



The Bristol meeting of the British Association was a great success 

 in many ways, but entomology did not seriously contribute to the 

 bulk or importance of the proceedings. Prof. Poulton, in fact, pre- 

 sented the only papers that were clearly entomological. One of these, 

 viz., " The proof obtained by Guy A. K. Marshall that Precis 

 octavia-natalensis and P. sesamus are seasonal forms of the same 

 species," was illustrated by the parent specimen of the red form, 

 which laid three eggs, and the butterflies bred from two of these, 

 one of which was of the black form, and the other a somewhat 

 modified red one. The other paper, by Prof. Poulton and Miss Cora B. 

 Sanders, " An experimental enquiry into the struggle for existence 

 in certain common insects," related certain experiments on pupa) of 

 Aglais {V(messa) nrticae, of which we shall probably hear more when 

 the results have been fully worked out. The experiments consisted 

 in exposing pupse of A. vrticae in various as natural situations as 

 possible, trees, rocks, palings, etc., and noting whether they remained 

 till emergence or disappeared. The modus operandi, and the many 

 difficulties that had to be encountered and overcome in the experi- 

 ments, were narrated by Miss Sanders. The total number of pupa) 

 exposed was something like GOO, about 100 in the grounds of 

 Magdalen College, Oxford, and the remainder in Switzerland, and in 

 the Isle of Wight. The most important result obtained was that 

 there is most unquestionably an intense struggle for existence in the 

 pupal state in A. nrticae ; at Oxford, amounting to almost complete 

 extinction, only 4 % surviving. In Switzerland (Miirren), a majority 

 escaped, whilst in the Isle of Wight there was a greater equality 

 between those that fell a prey to enemies and those that survived. Prof. 

 Poulton was not able to assert that the colour of the pupa had any 

 decisive effect on the result, but in one little group of pupje exposed on 

 trees two light pupa3 were the first to disappear, whilst golden pupns, on 

 nettles, were comparatively safe, and so far, the results pointed rather 

 to such protection from colour being shown ; but it remains for a 

 full analysis of the observations to be made, before the outcome 



