281 



are generally known. As howevcr tlic iiivostigators, who have 

 written on the setal })attern, have not paid any attention to these 

 familiar facts, I think it niay be useful to recall them to memory 

 and point out their connection with the arrangement of the setae. 



Tlie first who, I think, remarked the wing-rudiment in cater- 

 pillars, was Jan Sw^ammerdam, who described it in Biblia Naturae 

 II, p. 615 and in 1668 showed it to the Duke of Toscane, to 

 Thevenot and to Magalloti. He described it under the title of: 

 „Animal in animali or the butterfly hidden within the Caterpillar." 



The same thing is found in Historia generalis p. 202 as: „In- 

 sectum in Insecto seu Papilio in Eruca". In both cases Pieris 

 brassicae was the object of the investigation. The next investi- 

 gator who mentioned the wing-rudiment was P. Lijonet who in 

 1760 wrote his famous „Traite anatomique" and on p. 592 says: 

 „The isolated figure towards the bottom of the middle of PI. XI 

 is a mass of white satin-like stuff, placed in fat without sticking 

 to it and which is attached in B to the inner membrane of the skin. 



There are four such lumps within the Caterpillar (Cossus), ^hey 

 are found on either side of the 2ud and 3rd rings. They might 

 be the origin of the wings of the moth". And on p. 449: „It 

 is attached to the skin in the deep fold which it makes". 



With his well-known accuracy Lijonet draws many more 

 muscles in the thorax than in the abdomen and many of them 

 are not connected with the thoracic feet. — I think therefore, 

 that other differences besides these legs have been established be- 

 tween the thorax and the abdomen, so that Hennegüy's con- 

 tention (1904, p. 442), that in legless larvae all the segments 

 have exactly the same constitution, can only refer to external 

 features. 



The presence of the wing-rudiment combined with the absence 

 of the stigmata has induced many students to consider the wings 

 to be modified tracheae. 



But a good "many investigators who later on have examined 

 the djBvelopment of the wing, have come to the conclusion that 

 the first change does not start from a trachea but from the skin. 



