INTRODUCTION. 19 



respect, is like the T. longipalpi ; the intercalary vein of this 

 species issues from the angle between the cross-vein and the 

 discal cell, at the inner end of the latter. 



4. In the T. longipalpi a distinct fold generally runs across 

 the wing from the inner end of the stigma, over the discal cell, 

 to the penultimate posterior cell ; it is usually marked by a paler 

 coloring of the membrane of the Aving and by a discoloration of 

 tlie wing-veins ; it is more or less distinct in the diiferent genera. 

 In the T. brevipalpi this fold is not apparent, and a slight trace 

 of it may sometimes be observed in the partial discoloration of 

 the veins at the inner ends of the discal and of the penultimate 

 posterior cells. 



5. The T. longipalpi usually keep the wings divaricate in 

 repose, while the T. hrevipaljoi fold them over the abdomen. 

 Pedicia, which reminds us of the longipalpi by the length of the 

 last joint of the palpi, also keeps the wings divaricate in repose. 



6. The rostrum of the T. longipalpi is usually more pi'olonged 

 and its upper part projects in the shape of a point (?msi<.9), 

 clothed with hair ; a very marked character, seldom wanting 

 among the T. longipalpi, and not observed among the T. brevi- 

 palpi. 



t. The antennae of the normal types of T. longipalp)i are 13- 

 jointed ; those ot the T. brevipalpi are from 14 to 16-jointed; 

 exceptions are comparatively rare. The structure of the joints 

 of the fiagellum, common among the T. longipalpi, is different 

 from that of the majority of the T. brevipalpi. 



8. The male genitals of the T. longipalpi are of a more com- 

 plicated structure and more voluminous than the simple forceps 

 of the T. bi^evipalpi ; still, in this respect, intermediate forms 

 occur. 



9. The size of the T. longipalpi is generally considerably 

 larger ; their feet and especially the tarsi, are longer. 



The Ptychopterina, as I have said above, are an anomalous 

 group, which does not well fit in either of the two principal 

 divisions of the Tipididse. Their palpi are long ; but this length 

 depends on the elongation of all the joints and not of the last 

 joint in particular; this applies especially to the genera Proto- 

 plasa 0. S. and Tanyderus Philippi. The auxiliary vein in 

 Bittacomorpha and Pfychoptera ends in the costa, and there is 

 no cross-vein connecting it with the first longitudinal vein ; in 



