146 Mr. R. MacLachlan^s Monograph of 



Of the three great divisions of the Linnean Neuroptera 

 that I have up to the present time investigated for the 

 purpose of monographing, I have found the Planipennia 

 the most difficult ; — not on account of having been les3 

 attended to by authors, but that, these have almost in- 

 variably neglected the most important characters ; and 

 had I taken the advice of a valued continental corre- 

 spondent, I should have made tahulaui rasmu of all names 

 given before the last thirty years, and commenced anew. 

 Stephens' collection has enabled me to determine most 

 of his species with tolerable certainty ; but it is not to 

 him alone that the chaotic condition into which the 

 synonymy has fallen is due. 



Here, as in all other Neuroptera, the chief characters 

 are to be found in the structure of the abdominal seg- 

 ments, and the parts appended thereto -, and it is always 

 desirable that living insects should be examined when 

 that is possible. I have endeavoured to elucidate this 

 part of the subject as much as possible, and the numerous 

 illustrative figures have been lithographed from my own 

 drawings. The same remark will apply to the outlines 

 of neuration, a character also of great importance, espe- 

 cially for the discrimination of genera. 



Having spoken of neuration, it behoves me to enjoin 

 caution in deductions from this chai-acter. In many 

 Planipennia the veining is unstable both in species and 

 individuals ; and the Neuropterist must obtain that expe- 

 rience necessary to discriminate specific from accidental 

 or individual variation. 



The genus Hemerohius , as restricted, has been a cause 

 of great perplexity, and I can scarcely hope to have es- 

 caped serious errors. I believe, however, that the charac- 

 ters given will prove of service to those who may here- 

 after have the fortune to be able to improve upon them. 



The materials from which I have worked include 

 most of the British collections of these insects, the pos- 

 sessors of which have my thanks for their courtesy, and 

 especially am I beholden to the veteran Entomologist, 

 J. C. Dale, Esq., for his great kindness in committing to 

 my care unique and valuable specimens. My Continental 

 collection is very rich in Hemewhiidce j it contains many 

 type-specimens named by Schneider, and others that I 

 owe to the co-operation of Herr Brauer. Thus it is 

 hoped that, though imperfect in many respects, this 

 monograph may prove useful as a starting-point for 

 future investigators. 



