THE TRA CREATION OF WINGS 27 



THE BASAL CONNECTIONS OF THE TRACHEA OF THE WINGS 



OF INSECTS 



By Royal Norton Chapman, M.A. 



This paper is the result of an investigation undertaken at the suggestion 

 of Prof. J. H. Comstock, under whose direction the work has been done. 

 The purpose of the work has been to determine the generahzed type of the 

 basal connections of the tracheae of insect wings and to ascertain what the 

 principal lines of modification have been, with the hope that the conditions 

 of the basal connections of the tracheee may offer some explanation for 

 some of the modifications of the tracheae in the wings themselves. 



It v/as found by Comstock and Needham {American Naturalist, xxxii, 

 1898, p. 88-89) that the tracheae that supply the wings with air arise from 

 two distinct trunks, an anterior costo-radial trunk and a posterior cubito- 

 anal trunl<. In certain generalized insects these two trunks are distinct; 

 where this condition exists the medial trunk is a member of the costo-radial 

 group of tracheae. In most insects there has been developed a transverse 

 trachea connecting these two groups of tracheae, the transverse basal 

 trachea (Fig. 1 7, tb).* When a transverse basal trachea is formed, the base 

 of the medial trachea tends to migrate along it towards the cubito-anal 

 group of trachccB, and often becomes united with that group. 



Comstock and Needham were unable to explain the cause of the forma- 

 tion of a transverse basal trachea and the migration along it of the base of 



*Lettering of the Figures Iillistratixg the Basal Connections of the 

 Trache.e of the Wings of Insects. 

 a. c-r, accessory costo-radial trachea; 

 a. cii-a, accessory cubito-anal trachea; 

 a. dt, accessory longitudinal trachea; 

 as, anterior stem of the leg trachea; 



c, costal trachea; 



c-r, costo-radial trachea; 

 cu-a, cubito-anal trachea; 



d. It, dorsal longitudinal trachea; 

 g, tracheal gill; 



at, gill trachea; 



I2, mesothoracic leg trachea ; 



/a, metathoraeic leg trachea; 



//, longitudinal thoracic trachea; 



mt, muscle trachea; 



p$, posterior stem of the leg trachea; 



r. spi, rudiment of the mesothoracic spiracle; 



r. sp'z, rudiment of the m.'tathoracic spiracle; 



r. 5/J3, rudiment of the first abdominal s])iracle; 



sp\, mesothoracic spiracle; 



sp-z, metathoraeic S]nracle; 



5p3, first abdominal si)iracle; 



spi, second abdominal spiracle; 



tv, transverse basal trachea; 



u, union of the costo-radial and transver.se basal traclieae; 



vlt, ventral longitudinal trachea; 



V. sp2, vestige of the metathoraeic spiracular trunk; 



V. sp3, vestige of the first abdominal spiracular tnmk. 



