The origin and development of the wings of Coleoptera. 545 



in the Coleoptera they become functional early in the prepupal stage 

 without an ecdysis. This is accomplished by the partial ecdysis of 

 the dorsal tracheal trunk and the rupture of the intima in several 

 places through which air passes to the space formed between the two 

 intimas. As a result of this the tracheoles become functional in L. 

 decemlineata one or two days before the larva ceases feeding or on 

 or about six or eight days before pupation. 



The simplest condition of these tracheoles observed was in G. 

 hipunctata (PI. 18, Fig. 43), where the tubules are developed at ir- 

 regular intervals from the dorsal tracheal trunk and are not numerous. 

 A more complicated condition is found in L. decemlineata, where a 

 large mass of rather large tracheoles have entered the wing cavity 

 (PI. 18, Fig. 44), and a still more complicated condition is found in 

 0. scabra (PI. 18, Fig. 46). In this beetle a much coiled mass of 

 large tracheoles develop from the branches of the dorsal tracheal 

 trunk which enter the wing. In early prepupal life the foramen of 

 the wing is closed by a plug of these tracheoles. The most specialized 

 condition observed in the Coleoptera was found in the Buprestidae 

 where there develops from the hypotrichal membrane of the dorsal 

 tracheal trunk a mass of cells in which develops a great number of 

 coiled tracheoles (PI. 18, Fig. 45), the whole arrangement resembling 

 very closely the condition found in the Lepidoptera. 



The tracheoles are not entirely devoid of taenidia and have a 

 delicate intima, probably of chitin. They penetrate into the wing even 

 to its farthermost parts, but for the major part of their course in the 

 wing they follow the veins, ramifying from this path into the tissue 

 on either side. The tracheoles remain functional throughout the 

 prepupal period and are found in the early pupae, showing that they 

 are not all, and that perhaps not any of them are pulled out at 

 pupation, as Gonin (1894) supposes to be the case in Lepidoptera. 

 As the pupal stage progresses they become less and less numerous 

 and much broken up until eventually, in the late pupal life they are 

 absent. They are evidently digested in the haemolymph for frequently 

 fragments are found showing stages in degeneration; no further trace 

 of phagocytic action was observed, so the loss of these tracheoles is 

 undoubtedly due either to the action of solvents in the haemolymph 

 or to ferments (enzymes). 



b) Adult tracheal System. 

 The tracheae of the pupal and adult wings of the dorsal tracheal 



Zool. Jahrb. XVII. Abth. f. Morph. . gf^ 



