300 THE WINGS OF CO LEO PT ERA 



An extended series of papers on the venation of the hind wings of Coleop- 

 tera has been pubHshed by Kempers ('gg-'og). This contains excellent 

 figures of the venation of the hind wings of representatives of many families. 

 But as these studies are based entirely on studies of the wings of adult 

 insects, it is desirable that the conclusions regarding the homologies of the 

 wing-veins should be confirmed by ontogenetic studies. 



There has recently appeared, however, a contribution to our knowledge 

 of the tracheation of the wings of Coleoptera based on a study of the wings 

 of pup£e ; this is by Kiihne ('15). This author gives figures of the trachea- 

 tion of the fore wings of pupse of four genera of beetles and of the hind wings 

 of pupae of seven genera; but in only one genus (Cantharis) are the basal 

 connections of the principal tracheae shown. 



In this genus the radial trachea has not followed the medial trachea in 

 its migration along the transverse basal trachea towards the cubito-anal 

 group of trachege to so great an extent as Comstock and Needham found it 

 had in the cerambycid pupal wings represented by Figure 308. This is 

 markedly the case in the hind wings of Cantharis as figured by Kiihne; 

 but in one of the fore wings of Cantharis figured by this author, his Figure 7, 

 the radial trachea has evidently begun its migration towards the cubito-anal 

 group of tracheae. 



With this limited amount of data before him Kuhne concludes that the 

 labeling of the tracheae of cerambycid pupae given by Comstock and 

 Needham is an incorrect one, and that the radial trachea always remains a 

 member of the costo-radial group of tracheae. 



When we consider the great differences in the extent of the migration of 

 trachea R within the order Orthoptera, as is shown in Chapter VII, one is 

 not warranted in making generalizations regarding the conditions in the 

 Coleoptera after studying the basal connections of the tracheae in the wings 

 of a single genus of beetles. As yet I see no reason for changing the labeling 

 of the tracheae in Figures 308 and 309. 



It is evident from this review of the literature of the subject that much 

 remains to be done before our knowledge of the homologies of the wing- 

 veins of the Coleoptera can be regarded as fiiTnly established. 



The solution of the problem is rendered difficult by the fact that in no 

 coleopterous pupa yet examined have the principal wing-tracheae retained 

 the mode of branching characteristic of the hypothetical primitive type; 

 in most cases the tracheae extend in nearly direct lines with only small, 

 irregularly arranged branches. It seems also to be made more difficult by 

 another factor, namely, that the observations that have been made indicate 

 that in the Coleoptera, as in the Hymenoptera, the venation of the wings 

 precedes their tracheation. The courses of the tracheae, therefore, are 

 determined by the nature of the highly modified venation. 



