( xciii ) 



of Le|>idoi)terii e\-hil)itiiif; the same kind of iii:'(li;iii space, coutrastiui,' with the 

 rest of the wing either by being different in coLinr or by the absence of lines 

 transversely to the veins. The apjiearance of a "stigma"' or a kidney-shaped 

 mark ou the wings of so many Lp[iidoptera is the direct consequence of the 

 possession of cross-veins. Since the division of the wing-membrane is so 

 similar in the various groups of Lepidoptera, it is only natural that there are 

 many jioints of agreement in the ])attern of species belonging to not nearly 

 related groups. It is not the occurrence of this kind of similarity which is 

 astonishing, but that it does not occur everywhere, and that — bearing in mind 

 the remarkable phenomenon of " Mimicry " — Nature has abandoned in most cases 

 similarity, thongh it offers such great jirotection to the species, as we must assume 

 it to do, judging from the great number of cases of " protective " resemblance 

 at which Nature has arrived in a roundabout way. However, notwithstanding 

 the differences — in the first instance the outcome of segregation — outweighing 

 the similarities, the agreement in some such detail as referred to aliove, which 

 resemblance is the result of a general agreement in tlie structure of the insects, 

 is the starting-point for a development towards more conspicuous similarities. 

 The pale superciliary stripe, for instance, is continued in many Sphingidae over 

 the pronotum and along the sides of the mesonotum ; a mesial stripe begins 

 betweeu the two lateral ones on the occiput and runs over the thorax, ending 

 on the abdomen. The lateral lines converging frontad, the three together are 

 similar to au arrow. The same arrow-pattern is met with in other orders of 

 insects — for instance, in Coleoptera (Cttrrii/ionii/'ir, Cerumbijcidae, etc.) ; and 

 the agreement extends even further, the mesial vitta being either simple or 

 divided into two lines, and these lines being either parallel or divergent behind, 

 in the Hawk Moths as well as the Beetles. Moreover, the mesial vitta of 

 the head and thorax becomes a sutural vitta on the elytra of Coleoptera, and 

 similarly the hinder edge of the forewing of Lepidoptera, which corresponds 

 to the sutural edge of the elytra, assumes often the pale colour of the thoracical 

 mesial vitta in those Heterocera in which the wings have a roof-shaped position 

 over the abdomen when the sj)ecimen is at rest. The consj)icuous colouring 

 (scaling, pubescence, or pigmentation) of the mesoscutellum found in many 

 insects and the three rows of spots so frequently occurring on the abdominal 

 sternites belong to the same kind of resemblance as the thoracical vittae, the 

 respective markings being homologous in the various insects, evolution starting 

 from similarity and resulting in higher resemblance. In structure the same 

 jihenomenon is no less frequently observed. Here we may conveniently dis- 

 tinguish between similarities arrived at by retrogressive and by progressive 

 development. 



Reduction of organs occurs very commonly among Sphingidae, and leads often 

 to the loss of the organs. The disappearance of the horn of the larva in some 

 Vhilamjielinae and Ambiilicinae and in La para {Acherontiinae) ; the reduction of 

 the tongue-sheath of tlie pupa in Ambtdirinae and several Aclicrunttiiiae ; the 

 absence of an externally visible sheath of the anterior femur of the chrysalis in 



