138 University of California Publications. [Entomology 



ing to overthrow the conceptions in regard to the nature of 

 the- elements of this venation which have stood the test of 

 practical use in the system of nomenclature adopted by the 

 systematists. 



If the suggestion made, when considering the venation of 

 the Phryganseidse, in reference to the ancestry of this group, 

 is to be given any weight; if the homologies I have indicated, 

 which were determined on purely anatomical grounds, are to 

 be given any weight, they will entirely support the system of 

 nomenclature here proposed. In most schemes of classifica- 

 tion the Hymenoptera are placed nearer the Diptera than to 

 the Lepidoptera. The structure, however, really supports the 

 suggestion of relationship shown by the resemblance of the 

 larva^ of sawfiies and those of moths. These two orders are 

 the youngest groups, since the Diptera are shown by the 

 geological record to be distinctly older. The suggestion of 

 Phryganjeid origin is a very attractive one, for if the figure 

 of the fore wing of Chloropsyche is compared with that of 

 the Hymenoptera, the veins supposed to be suppressed will, 

 in each case, correspond with irregularities in the course of 

 veins not otherwise easily accounted for. Thus there is a 

 vestigial structure shown in many Hymenoptera, indicating 

 the suppression of a longitudinal vein in the median and first 

 two discoidal cells, and the lanceolate cell in sawflies suggests 

 the lacking posterior veins. If all these are added and the 

 third transverse cubital and second recurrent suppressed and 

 each longitudinal vein forked, we have exactly the venation of 

 the front wing of Chloropsyche. The hind wing of Helico- 

 psyche corresponds very closely with the venation of the hind 

 wing of a sawfl3^ 



LEPIDOPTERA. 



Throughout the greater part of the Lepidoptera the venation 

 is remarkably uniform. The wings are notably free from cross 

 veins, and the number of longitudinal veins is small, even 

 though some of the insects in this order are very large, the 

 largest of any existing insects. Increase in size in this order 

 evidently does not have any necessary influence on the vena- 

 tion. Extremely small members of the order, however, often 

 exhibit decided decrease in the number of veins, giving us thje 

 only types that cause any trouble in determining the homologies. 



