THE WINGS. 9 



(bifid) (PI. XY, fig. 10), simple (1. c. fig. 8), or with a 

 minute tooth not far from the apex (PL XV, fig 9). 



Croesus has the basal joint of the tarsus flattened 

 into a plate-like expansion, the posterior tibiae being 

 also thickened towards the apex. Some species of 

 Nematus have the apex of the hinder tibise thickened, 

 and often grooved on the inner side. 



The icings are (with one exception*) always present, 

 and four in number, the two anterior being much the 

 larger pair. They are broadest at the apex, which is 

 rounded (PI. X, fig. la). In texture they are mem- 

 branous. The front border (the costa) is thickened, 

 and towards the apical third of the wing is a thickened 

 spot called the stigma (PI. X, fig. 1 st), which is often a 

 conspicuous object, especially when it projects above 

 the costa, as it does with Pachylostica. 



Generally the wings are hyaline and often iridescent, 

 but with some species they are coloured, either in 

 patches or throughout, the usual colour in either case 

 being black, although with many exotic forms it is 

 bluish; and, in the latter case, it has occasionally a 

 metallic lustre, the wings themselves being of a thicker 

 texture than usual. 



Proceeding from the base of the wing towards the 

 apex, but seldom reaching much beyond the stigma, 

 are four nervures, while from the neighbourhood of 

 the base of the stigma, other two nervures run to the 

 apex in a slightly curved fashion. Intersecting these 

 transverse nervures, are shorter longitudinal ones, so 

 that, in this way, enclosed spaces are formed, to which 

 the term cell or cellule has been applied. As the form 

 and position of these nervures are remarkably constant, 

 and, as the presence of a particular arrangement of the 

 nervures carries along with it peculiarities in other 

 parts of the animal's structure, great attention has 

 l3een paid to them, especially as to their use in the 

 definition of genera. In this relationship the cells 

 formed by the transverse nervures which run from the 

 * Pompholyx, Freymouth, which has the 9 apterous. 



