21 
It is, however, impossible to say what may ultimately arise from 
the study of neuration when its true nature, and the lines on which 
its modifications have proceeded, are more fully known and under¬ 
stood. It is well-known that in the less specialised Orders of Insecta 
—Orthoptera, Odonata, &c. —the neuration is exceedingly complicated ; 
that as we reach the Trichoptera a simpler system prevails, but some¬ 
what more complex than that found in any Lepidoptera. It has been 
long mooted, however, from various observations, that the Lepidoptera 
and Trichoptera are somewhat intimately related, and that the former 
probably originated from the latter, and for several reasons the Micro- 
pterygides are supposed to be the nearest existing lepidopterous super¬ 
family to the Trichoptera. Now the neuration of the Micropterygides 
resembles somewhat that of certain Trichoptera, and we find that in 
the former, as well as in Hepialides, the fore- and hind-wings have 
twelve nervures, whilst in these and others of the less specialised 
superfamilies the discoidal cell can hardly be said to exist as such. 
The neuration displayed by Micropterygides and Hepialides may be 
looked upon as the most ancestral form now to be found in the Lepi¬ 
doptera. As we pass on through the more specialised families and 
tribes, we find that the nervures frequently become fewer in number, 
and the cell becomes a very marked feature of all the more specialised 
groups. It follows, therefore, from our previous statements, that the 
more complex neuration as exhibited by the Micropterygides and 
Hepialides is the older and more generalised form, the simpler neural 
arrangements the more recent and more specialised. It must be con¬ 
fessed that this looks at first sight somewhat paradoxical, but it is 
readily seen to be logically true. 
In neuration, however, there is one difficult point which has never 
been quite cleared up. It is this—that whilst the process of evolution 
may lessen the number of main nervures by various processes of 
selection, and thus produce a specialised type according to the general 
laws laid down above, yet, when that specialised condition has been 
reached, it is not only conceivable, but extremely probable, that 
conditions may arise which may necessitate the complication of some 
particular neural branch for a specific purpose, and thus we may 
understand that, although the simplification of the neuration must of 
necessity indicate a high degree of specialisation, yet it is possible 
that a complicated condition of some particular branch of a nervure 
may also indicate a high degree of specialisation. I do not know 
whether I can illustrate this at all clearly, but I can try to do so. 
In the diagram (Plate I) illustrating the neuration of the fore-wing of 
Pajnlio machaon, it will be noticed that the nervures are numbered 
from the base upwards as 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12. This 
must be considered, as I have before remarked, a very generalised form 
of neuration. It will furthur be observed that 2, 3, 4, 5, 6 are 
branches of the median (or cubitus) nervure, whilst 7, 8, 9, 10, 11 are 
branches of the subcostal (or radial) nervure. It happens that, in some 
Lepidoptera, the discoidal cell is open between 6 and 7, and hence we 
obtain the knowledge that 6, coming out from the centre of the front of 
