Ainil, 1S99.1 77 



NOTES ON CERTAIN PAL.EA.RCTIC SPECIES OF THE GENUS 



HEMEROBIUS. 



No. 1.— INTRODUCTORY REMARKS and the Geoup of H. NERVOSUS. 



BY ROBERT McLACHLAN, F.R.S., &c. 



It has long been evident to workers on the European species o£ 

 this genus (as now restricted) that specific determination is often 

 difficult. 



When in 1868 (Trans. Ent. Soc. Lond., 1868, pp. 145, et seqq.) I 

 published my "Monograph of the British Neuroptera-Planipennia,^' I 

 made what was probably the first extended attempt at elucidating the 

 subject by descriptions and figures of the male appendages. The 

 remarks at p. 175 of that Monograph as to synonymy and structure 

 obtain almost equally well now, after the lapse of more than thirty 

 years, as then. But it is perhaps possible to throw a little more light 

 on the subject. More than ten years ago I had in view a Revision of 

 the palsearctic species, and had prepared fresh figures of the anal parts 

 for several of them. About that time it was considered advisable 

 that I should abandon, at any rate temporarily, camera lucida drawing, 

 and having once abandoned it, the difficulty of resuming it became 

 apparent when attempted. Ever ready to assist me, and influenced 

 by the fact that at least two British species have never been properly 

 elucidated, my friend and former pupil (in Neuroptera), Mr. K. J. 

 Morton, kindly came to my aid, and supplied the necessary drawings. 



I think it possible, in most cases, to separate the males by the 

 anal structural characters, and these notes mainly conce n these 

 characters. Of course, in most cases, the females can be rightly 

 assigned to their proper partners by general characters, but I am not 

 yet able, in the majority of cases, to bring forward structural anal 

 differences in that sex, and there are several instances in which the 

 males show very striking anal structure, rendering differentiation 

 easy, but in which I am not yet quite able to satisfactorily identify the 

 respective females when, as is often the case (for the females seem 

 more plentiful), unaccompanied by the males from the same locality ; 

 and even if the males be present, it happens that two species very 

 similar in general aspect often occur together. Time, and more careful 

 observations, especially in the field, will no doubt remedy this, and 

 possession of the key once obtained, future workers will probably find 

 all difficulties vanish. 



It is scarcely necessary to remark that the numerous extra- 

 palaearctic, especially North American, forms, can never he satisfactorily 

 elucidated unless treated in the same manner. In connection with this 

 it is necessary to give a warning to the effect that certain [jala^arctic 



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