( Lxxiv ) 



arrangement, however, being ]]reservecl. The nniserial spination is f'oiinil only in 

 Pseudospliinx and allies, Farlii/lin and allies, a number of Xylophnnes, and in 

 Pliolus — i.e. in generalised forms of the Sj/hiixjidar ^emaiiopliorae. 



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

 donbt on this point, if one compares Atemnom and Macroylo.t.vim, and the 

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

 one direction. Which, however, is the original spination of Spliingidae ? Does 

 the weak spination of the higher Ambidici/iue and Acherontiiiuu' represent the 

 generalised state, or is a stronger chitinised type more ancestral ? 



There is a complete gradation from Cres.^oitia, Lcuigia, etc., without spination, 

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

 spination of l'l<oUi>t, Pseudoitphiiix, etc. Spination is certainly a sjiecialisation. 

 It is restricted to the Sphiinjidae, the only approach to spination we know of 

 being fonnd in the American Ca.ifii/'it/rte. Therefore one cannot seriously donbt 

 that the ancestral Heteroceron from which the family Splimyidae has arisen 

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

 early Sphingid also s])ineless ? 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 quantitative gradations from a to ~, the student 

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

 ment. The ))resence of such a series is, however, no ])roof whatever that the 

 quantitatively lowest degree is the jiylogenetically 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 sjiination would be the few species which 

 have no sjiines (Cressonia juglandis, Lanyia zenzeroides and Li/cosphiiigia 

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

 these weakly spined Hawk Moths are weak also in other resjjects ; 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 tyjies. It is true, a specialised insect may have 

 l)reserved one or more generalised characters ; but it would be very singular, 

 — and is surely imjirobable — if such a number of species of various subfamilies 

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

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

 j)robability is altogether in favour of the weak spination being also a 

 character acquired — i.e. that the weak spination is the result of the reduction 

 of a stronger sjiination, as the short tongue, the short antennal end-segment, 

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



The first alidominal segment («/' and pp, PI. LXII. f. 6. 8 ; PI. LXIII. f. 1) 

 consists of a tergite («<') and a more or less triangular lateral plate, the 

 paraj)leura {pp). The tergite' varies much in length, and offers distinguishing 

 chara('ters, being, for instance, reduced to a very narrow stripe in Macroglosstim 

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



