( xciii ) 



of Li'})iil(i[itcra rxliihitiug the same kind of iiu'iliiiu sj)iK-e, outrastiu;^ with the 

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

 transversely to tlie veins. The aj)jiearance of a ''stigma" or a kidney-shaped 

 mark on tiie wings of so many Lepidoptera is tiie direct consequence of the 

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

 similar in the various groui)s of Lepidoptera, it is only natural that there are 

 many joints of agreement in the pattei'ii of sjiecies belonging to not nearly 

 related gronjis. It is not the occurrence of this kind of similarity wiiich is 

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

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

 similarity, though it offers such great protection 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 difierences — in the first instance the outcome of segregation — outweighing 

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

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

 is the starting-point for a clevelo[)ment towards more conspicnous similarities. 

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

 the pronotum and along the sides of the mesonotuin : a mesial stripe begins 

 between the two lateral ones on the occi{)ut and runs over the thorax, end'ng 

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

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

 insects — for instance, iu (Joleoptera {Currulionidae, Cerambi/cidne, 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, tlie mesial vitta of 

 the head and thorax becomes a sutural vitta on the elytra of C'oleoptera, 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 Heteroccra iu which the wings have a roof-shaped position 

 over the abdomen when the specimen is at rest. Tlie conspicnous 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. 



Kednction of organs occurs very cdmnionly among Sjjlihu/id'ie, and leads often 

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

 Fhilampelinae and Ambulicinae and in Lapara (Aekeronfi/nae) ; the reduction of 

 the tongue-sheath of the pupa iu Ambulicinae and several Ac/terontiinae ; the 

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



