296 THE entomologist's RECORD. 



Thrush, whose habits are very much the same, is supposed to be 

 protectively coloured. In the course uf my wanderings in the barest 

 and most remote parts of the South Downs, I have found it almost 

 impossible to get out of range of the Blackbird's note (not that one 

 wants to), but the Song Thrush is absent. If there is only one gorse 

 bush, there you will find a Blackbird nesting and advertising its 

 presence on the top of the bvish by its song. Yet here Hawks are 

 plentiful and the Downs are regularly quartered by Peregrine Falcons, 

 Sparrow Hawks and Kestrels. If the reverse was the case, c/c, the 

 Song Thrush present and the Blackbird absent, it would probably be 

 suggested that the former, being protectively coloured, enjoyed 

 immunity from attack, and the latter through being conspicuously 

 coloured had been killed off. One reason for the absence of the 

 Thrush is that it likes a high tree from which to sing, and haunts the 

 clumps of trees, which are sparsely scattered in some parts of the 

 Downs. 



Mr. Curtis says on p. 153 in speaking of the increasing discrimina- 

 tion of the birds, "«.s tite dbcriialnative facultij iroiiUl be enlianced in each 

 (/cneratioii bij the fact that the bird who successfidli/ diacriniinated, ivould 

 hare a better area of food siipjdy, because it icoiild be nitre of palatable 

 insects all tiie time, instead of c/ianrin// unpalatable insects." 1 agree. 

 The bird would not need to chance the "unpalatable" insects, 

 however, but would make use of the above discriminating faculty and 

 •devour the supposed " mimic." Does Mr. Curtis not see that this 

 undermines the theory of mimicry and the end for which it is supposed 

 to be working, viz., the protection of the "palatable" species. With 

 regard to Models p. 154, it is news to me that Leucoma salicis, 

 Spilosonia liibrici/ieda and -S'. iiienthastri come under this head, as I have 

 frequently found their severed wings, also those of the Wood Leopard 

 Moth, Zeuzera pi/rina {aescnli), a most evil smelling moth, under 

 electric arc lamps. On what difference, I wonder, does Mr. Curtis 

 base his assumption that Porthesia chri/sorrhoea is palatable, and 

 S. Inbricipeda and S. iiienihastri unpalatable ? From a field natura- 

 list's point of view the models and mimics suggested on page 15-1 are 

 about the limit. His admission that he does not know the " models " 

 for J'lijeria tabaniforuiis, etc., and his guess that " they are certainly 

 Hymenopterous insects which are probably armed in some way," is not 

 evidence. Surely it would have been uiore scientific to obtain positive 

 evidence before putting the claim forward. Mr. Curtis in the last 

 paragraph on p. 154 says "looking at the above list it is obvious 

 to the most superficial person that the earliest appears after birds 

 have received an immense accession of numbers by the migrants' 

 arrival, that insect life is at its highest point, etc." My interpretation 

 of the above is that the warmer weather induces more species of insects 

 to emerge and the same cause induces our summer migrants to return. 

 Were there not a sufficient insect diet we should not get them. 

 Further, insect life being at its height, there is more chance of finding 

 some species resembling others than when insect life is at its lowest. 



It is past my comprehension why " it is an inteyral part of the 

 t/ieories that warning colours lose their utility, to a larye e.rtoit, ir/ien 

 insect food is scarce." I should have thought the palatable insects 

 needed them more at this time. Mr. Curtis says nothing here 

 (although he mentions them later on) about the large influx of insect- 



