714 THE PANORPOID COMPLEX, ill., 



It is evident that the retinacula, being developed upon the 

 underside of the wing, will attain the most advantageous position 

 if they are developed either on or near those veins which project 

 most below the general level or plane of the wing-surface. The 

 concave veins are Se, M and Cu 2 ; of these, M lias been eliminated 

 during the formation of the basal cell. Text-fig. 10 b, shows 

 diagrammatically the mechanical advantage of the positions in 

 which the two retinacula actually occur. 



Dr. Turner also points out that both subcostal and subdorsal 

 retinacula occur commonly in the males of Noctuidae, Arctiidae, 

 Liparidae and Pyralidae, and can sometimes be detected in the 

 Geometridae. He infers that "this double arrangement is the 

 rule in the Heteroneura." Also, "in at least some female Noc- 

 tuids there is an attempt at a subcostal retinaculum, though I 

 cannot say that it is functional." He also draws my attention 

 to the following interesting point: — "If you consult Sir G. 

 Hampson's Catalogue of the Lepidoptera PhalamaB, vol. XL, you 

 will find that the subfamily Acontiinae have normally a bar- 

 shaped subcostal retinaculum in the male, but that, in some or 

 all species of some genera, e.g. in Earias, this has been lost, and 

 the frenulum articulates with the subdorsal retinaculum, as in 

 the female. It is remarkable that, in two closely allied species, 

 the male in one may have a well-developed subcostal bar-shaped 

 retinaculum, in the other not." 



There is, evidently, still a wide field of research open in the 

 study of the evolution of the frenulum and its retinacula within 

 the Lepidoptera Heteroneura . 



Appendix C. 



Note on the Besting-Position of the Wings in the Panorpoid 



Camplex. 



During my research upon the Panorpoid Complex, the Resting- 

 Position of the Wings was carefully studied, with a view to 

 giving a separate Part on this subject. The conclusions arrived 

 at, however, show that no phylogenetic results of value can be 

 attained, as regards the separate Orders. All the Orders of 

 the Complex exhibit archaic types in Which the resting-position 

 is stegopterous, i.e. the wings are held, when at rest, in a slanting 

 roof-like manner over the body. The angle of inclination of the 

 wings depends, not only on their width, and the stoutness of the 



