( Ixxiv ) 



arraiijii'iiiciil, liowi'vor, beiiij,' jirescrvcd. Tlic miiscrial spiMatioii is I'duiiil only in 

 l'.te}i(losjthinx and allies, Fachjilin, and allies, a number of Xyloph'Dic^, and in 

 Vhohia — /.('. in generalised forms of the S/thiiiyidae semanophorae. 



The second type of spination has arisen from the first ; there can be no 

 doubt on this point, if one compares Atemnora and MacrogloMum, and the 

 members of the Sesia series of genera ; it represents the highest specialisation in 

 one direction. Which, however, is the original spination of S/ihiiHiidae ? Does 

 the weak spination of the higher AmhiiliciiKie and AcJieronttinne represent the 

 generalised state, or is a stronger chitinised t} pe more ancestral ? 



There is a complete gradation from Cimso/iia, Laiigia, etc., without spination, 

 through the reduced SpluiKjuhie with weak spines, to the strong uniserial 

 spination of I'liolits, l'sei(clo»jiliiiix, etc. Sjtination is certainly a specialisation. 

 It is restricted to the SphiiKjidae, the only a]>proach to spination we know of 

 being found in the American Castniidae. Therefore one cannot seriously doubt 

 that the ancestral Heteroceron from which the family Spldngidae has arisen 

 was a Lepidopteron without abdominal spination. But was the abdomen of the 

 early Sphingid also spineless ? or was the acquisition of spination among the 

 first specialisations by which the early Sphingid deviated from its allies? 

 Where there is a series of ([nantitative gradations from a to z, the student 

 is easily inclined to consider a the beginning and z the end of the develop- 

 ment. The presence of such a series is, however, no proof whatever that the 

 quantitatively lowest degree is the j)ylogenetically oldest stage. The mistake 

 has been made, and will often be repeated no doubt. It is a very natural 

 and very convenient conclusion. If this view were correct in our case, the 

 Hawk Moths most generalised in spination would be the few species which 

 have no spines {Cregsoniu juglandis, Langia zenzeroides and Lijcosphingia 

 hamatus), and next would come a great mass of genera with weak spines. All 

 these weakly spined Hawk Moths are weak also in other respects ; they are 

 reduced and otherwise modified forms, showing reduction and modification in 

 the mouth-parts, scaling, legs, wings, and sexual armature ; they are decidedly 

 developments from less reduced tyjjes. It is true, a sj)ecialiseu insect may have 

 preserved one or more generalised characters ; but it would be very singular, 

 — and is surely improbable— if snch a number of species of various subfamilies 

 had all preserved the same ancestral spination, and become in other respects 

 so diversely modified. On the contrary, one is bound to conclude that the 

 probability is altogether in favour of the weak spination being also a 

 character accpiired — i.e. that the weak sjiination is the result of the reduction 

 of a stronger spination, as the short tongue, the short autennal end-segment, 

 the small palpus, the short spurs, etc., etc., are the results of reduction. 



The first abdominal segment {(W and )>p, V\. LXII. f. 6. 8 ; PI. LXIII. f. 1) 

 consists of a tergite {at^) and a more or less triangular lateral plate, the 

 paraplenra (/i}>). The tergite varies much in length, and offers distinguishing 

 characters, being, for instance, reduced to a very narrow strij)e in Macroglossum 

 and allies, while it is about half the length of the second tergite in Haemorrhagia, 



