( 15 ) 

 22. Catoria lucidata spec. uov. 



Foremng : white, with olive-green speckling only ; the lines, donMe, dark 

 olive-green, placed mnch as in delectaria Wlk., but the outer line conspicnously 

 angled on vein 6, not rounded ; lunules of the shade preceding submarginal line 

 marked with blackish beyond cell and between veins 7 and S, and 2 and 3 ; marginal 

 lunules and cell-spot black ; fringe white. 



Hindwing : like forewing ; cell-spot a black point, not an ocellus. 



Underside greenish brown clouded with velvety black before the white spaces 

 of the hindmargin, which are bright white, not cloudy as in delectaria ; cell-spot 

 of forewing velvety black, large and round ; of hindwing only a black point. 



Head and thorax pale greenish ; abdomen wliite, the basal segments edged 

 with brownish scales : antennal pectinations rufous ; in delectaria they are fuscous. 



Expanse of wings : 48 mm. 



1 6 from Guizo Island, Solomons, November 1903 (Meek). 



REMARKS UPON SOME THEORIES IN REGARD TO THE 

 MIGRATION OF BIRDS. 



BY \V. EUSKIN BUTTERFIELD. 



I SUPPOSE most persons who are acnuaiated with the literature of bird- 

 migration must feel that few of the theories with which the subject is 

 burdened compel assent. In the present paper I venture to put together under 

 the various headings such suggestions as appear to me to be of moment. 



INCENTIVES TO MIGRATION. 



The awakening of the impulse of migration in spring and autumn is often 

 confused with the proximate cause or causes of the sajjarate journeys by which 

 the whole migration in each direction is accomplished. The inherent stimulus is 

 doubtless felt in many, and perhaps in most, birds before the northward or 

 southward movement is embarked upon. The immediate incentive to migration 

 need not be the same for all species of migrants, nor indeed for all the individuals 

 of the same species ; moreover, the incentive to spring migration need not 

 be the same as the incentive to autumn migration. From the confusion 

 mentioned above, some writers have sought uniform causes competent to account 

 for each of the two great movements in all species. The incentives to these 

 movements may result, as I shall hope to show, from a variety of causes acting 

 alone or in concert, and in seeking them we need not concern ourselves with 

 the original cause of migration. 



Taking the autumn migration first,* scarcity of food is thought by many 

 authors to afford a sufficient explanation of the desertion of the summer quarters 

 by most species, although it is allowed that this cannot be the sole cause, since 

 it not infrequently happens — as in the case of our Song Thrush — that a breeding 



* For convenience, the series of journeys constituting each of the two great seasonal luovemt-'nts 

 requires to be denoted by a separate term, 



