( xciv ) 



^|iccit's (if viirions suht'iLiiiilifs of Sphnnjidac ; tlic loss (if tlic touijue in (sunie 

 Amhiiliriiuie iiiul Arhcrontihtue, of tlie proximal pnir of simrs, of the pnlvillus 

 and ])aroiiycliium, of the frcniilnm and retinacnlnni ; the rednction of the mid- 

 and hind-tarsal comb and of tlie paljii ; the rednction of the tarsal spines in 

 nnmber, of the tibiae and tarsi in length and of the head in size ; the loss of 

 the fascicnlated ciliae in the male antenna of l{liop((Iojj;/sclu\ of the .abdominal 

 spines in various Amhiilii-iniw, of the ]iatch of sensory hairs at tlie base of 

 the jialpi in \\w Spliiiigulae asemaiiflpJionn', and Gnrelca and allies among the 

 Sfihingidue scmanophorae, of tlie bristles on tlie jiilifer, etc., establish between 

 these Spkinqidac, as well as between them and other Lepidoptera, a similarity 

 in the jioints mentioned which is of importance for the jirojier 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 gronjis of Sphiiiyidae and other Lejiidoptera. 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 

 suppression 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 effaced. The 

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

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

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

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

 yellow abdominal side-patches in certain Acherontiiime 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 production 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 causes 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 residted in the effacement of the positive characters, replacing 

 the ])irture which was variegated in pattern and structure by a clean surface. 



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

 ])ositive ciiaracters in Spliingidae. The small head is frequently crested ; the 

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

 whi(Oi has very weak sjiines at the edges of the segments, is often spinnlose all 

 over the tergites or assumf^s a woolly appearance. Weakened power of flight and 

 broadened wings are frequently associated. The positive and negative characters 



