358 Annals Entomological Society of America [Vol. XII, 



remove the Micropterygidse from the Lepidoptera, would 

 necessitate the assumption that the Lepidoptera have originated 

 twice or have been derived from a hypothetical lepidopterous 

 ancestor so close to Micropterygidae that it can not be separated 

 from Micropteryidae. 



(b) Mode of Insuring Synchronous Action of Fore 

 and Hind Wings. 



The methods of holding the fore and hind wings together in 

 flight show characteristics which are of value in a study of the 

 phylogeny and relationships of the Trichoptera and Lepidoptera. 



In the more generalized Trichoptera and in the most primi- 

 tive groups of Lepidoptera, the posterior lobe of the fore wing 

 has been modified to serve as an organ for holding the wings 

 together, termed fibula or jugum, depending on mode of 

 functioning. The fibula in the more generalized Trichoptera, 

 such as Rhyacophila, and in certain of the Micropterygidae, as 

 Mnemonica in the subfamily Eriocraniinas, acts by pressing 

 downward over the base of the hind wing and clasping the 

 anterior tuberosity of the hind wing. Tillyard ('18, '19) has 

 described for certain genera of the two remaining subfamilies 

 of the Micropterygidse, the Mnesarchaeinae and the Microptery- 

 ginae, a different mode of functioning of the fibula. In these 

 genera it is described as being bent under the fore wing and 

 serving as a retinaculum for the series of costal spines of the 

 hind wing.* My observations on Epimartyria in the sub- 

 family Micropteryginse tend to support this view. 



The fibula in the female of the last specialized, genera of 

 Nepticulidae (which find their nearest allies in characteristics of 

 venation among the Hydroptilidae in the Trichoptera) is 

 identical in structure with the fibula in the more primitive 

 Trichoptera and in the Micropterygidae. In the Trichoptera 

 the process of modification of the fibula has finally resulted in 

 such a reduction in size and change in shape that the posterior 

 lobe of the fore wing no longer bears any resemblance to a 

 fibula and can not function to aid in holding the fore and hind 

 wing together. In some forms, while not retaining the char- 

 acteristic shape shown in the Rhyacophilidae, the longitudinal 

 free margin still shows the downward curve, thus indicating 



* That these spines do not constitute a true frenulum and are not homologous 

 with it, is shown in the pages following. 



