BY R. J. TILLYAKD. 589 



diverged from them by a reduction of tlie original meshwork, in 

 the course of which the pits, or bases of insertion for the maci-o- 

 trichia, became seated upon the membrane of tlie wing; just as, 

 in the Lepidoptera, the scales have appeared in a similar manner. 



The original pitted wing of the true Hemiptera may be con- 

 sidered to have given origin directly to the various wing-types 

 still extant amongst tlie older families of recent Homoptera; the 

 main developments in this latter Suborder are not to be found in 

 the wing at all, but in the specialisation of the head and antennae, 

 and in the development of the power of leaping. In this con- 

 nection, we should bear in mind that a number of Homoptera, 

 especially in the Cicadidat, still show the dividing line between 

 corium and membrane. 



We have now to consider the origin of the Heteroptera. For 

 this, we cannot take Prosbole itself as a starting point; but we 

 must go back a little way beyond this type, and assume a closely 

 similar ancestral form with a wing pitted all over. Keeping the 

 main scheine of venation unaltered, we may now see the origin 

 of the Heteroptera in a form in which tlie tendency of evolution 

 in the basal half of the wing was towards suppression of the 

 venation and hardening of tlie wing-membrane (with or without 

 loss of the pits); while, in the distal half of the wing, the cross- 

 veins of dense Fulgorid-like venation still preserved in Prosbole 

 become obsolete, and the remaining venation becomes greatly 

 altered, in correlation with the differentiation of the dividing- 

 line between corium and membrane. 



I think that a very little consideration, aided l)y a comparison 

 of the figures of Prosbole smd Dunsiania here given, must con- 

 vince us that Dunstania represents a very typical immediate 

 derivative from the hypothetical ancestor oi Prosbole, from which 

 we started in the preceding paragraph, along the lines there 

 indicated as leading directly to the Heteropterous type. That 

 is to say, Dunstania, though not directly derivable from Pros- 

 bole, is nevertheless closely related to it; but, while Prosbole 

 itself cannot be accepted as having advanced along the line of 

 the true Heteroptera, and must, therefore, be kept in a separate 

 Suborder PaUeohemiptera, Dunntdnia, on the other hand, has 



