( xc'iv ) 



species of vnrious t^ulif'aiuilies of Sjj/,/n,/,',/,tr : the loss of the tongue in some 

 Amhidiriuae i\m\ Arhcrfliitiimw, of the proximal |inir of spurs, of the jinlvilliis 

 and i)aronycliium, of the frenulum and retiuacnhim ; the reduction of the mid- 

 and hind-tarsal comb and of the palpi ; the reduction of the tarsal sjiines in 

 number, of the tibiae and tarsi in len.<;th and of the head in size ; the loss of 

 the fasciculated ciliae in the male autenua of Rhopalopi/sche, of the abdominal 

 si>ines in various Ambiiliriiiuc, of the patch of sensory hairs at the base of 

 the paljii in the Sp/ii/iffidae aseiiia»oj>liome, and Garelca and allies among the 

 S/,/ii)iffii/iif' xenxiiifl/ihornc, of the bristles on the pilifer, etc., establish between 

 these S/>//i)i(/ii/(ii; as well as between them and other Lepidoptera, a similarity 

 in the points mentioned which is of imjiortance for the proper comprehension 

 of the origin of agreements in structure, since there is no doubt that, at least 

 in most cases, these negative characters are independently acquired in the 

 various groups of S}jlii)itjiilae and other Le])idoptera. The loss of the wings 

 in a number of Lepidoptera, and of the hindwings in Diptera and many Beetles, 

 may be mentioned in this connection. The independent effacement of differences 

 in consequence of loss occurs also in pattern. Uniformity in colour may be 

 arrived at either by the exaggerated development of one colour leading to the 

 supjiression of a pattern, or by the markings disappearing on account of the 

 non-development of the pigment (or of the particular structure in case of 

 structural colours). The pattern is in most cases only partially effiiced. The 

 partial transparencies of the wings as found in Cocythis and some Haemorrhagia 

 have no more to do with one another than Lave the entirely white anterior 

 wings of some Beetles (elytra) and Butterflies. The loss of markings in Mimas 

 tiliae is as independent from that of Amorpha populi, as is the disappearance of 

 yellow alidominal side-patches in certain Acheroniiinae and some Macroglossum. 

 The pale colour frequently exhibited by a large percentage of specimens 

 which are obtained by breeding in and in — for instance, in Amorpha populi — is 

 due to the meagre jiroduction of dark pigments, and reminds one of the pallid 

 cave-insects. The weakening effect of breeding in and in and the result of a 

 life in dark caves are, therefore, similar in so far as both lead to the loss of 

 pigment, producing clayish ochraceous forms. The causes are different ; the 

 result is similar. Indeed, if the numerous cases of the disappearance of 

 distinctions in structure, colour, or jiattern are inquired into, it will be found 

 that the canses of the loss of distinctive positive characters and the reasons for 

 their disappearance are as different as the starting-points of the retrogressive 

 development which resulted in the effacement of the positive characters, replacing 

 the jiictnre which was variegated in pattern and structure by a clean surface. 



The reduction of organs is often accompanied by the appearance of certain 

 positive characters in Sphingidae. The small head is frequently crested ; the 

 small eyes become lashed, and the reduced tibiae often spinose. The abdomen, 

 which has very weak spines at the edges of the segments, is often spinulose all 

 over the tergites or assumes a woolly appearance. Weakened power of flight and 

 broadened wings are frequently associated. The positive and negative characters 



