130 [June, 



worth while to give a figure of this as it appears after the sedeagus 

 has been mounted in balsam. Whether the ill-shaped body is or is 

 not the remains of a spermatophore I am quite unable to say. 



Although no information exists as to the copula of Gyrinus, we 

 owe to Eegimbart (Ann. Soc. ent. France, 1883, p. 383) a brief but 

 most intei-esting account of the phenomenon in Orectochilus ; and 

 from his description it is very probable that the object shown in the 

 above figure is part of what he calls a " cylindre spermatique."* 



The species of this genus are liable to a peculiar form of variation, 

 the chitin of the upper surface — more especially of the elytra — becoming 

 more or less dull, instead of highly polished ; and this dullness is 

 sometimes accompanied by the development of an excessively minute 

 and indefinite sculpture. As sculpture is of considerable importance 

 in discriminating the species of the genus it is desirable the student 

 should be prepared to recognise this adventitious roughening of the 

 surface when he meets with it. I have seen it in G. natator (where 

 with a concomitant change of colour it forms the var. corjmlentus, 

 Schatzm.), in colymbus, bicolor, elongatus, rnarinus, and minutus, and it 

 probably occurs in the other species if larger series of them were 

 accessible. 



The following table may help in the difficult task of distinguishing 

 the species, but the study of the a3deagus is essential for certainty : — 



1 /4 !) Scutellum with a small elevation at base 1, minutus. 



) Scutellum without elevation. 



) Under surface entirely yellow 2, xwinator. 



) Under surface more or less extensively black. 



o ^io) Inflexed margin of elytra largely or entirely yellow. 



6 (7) Surface of elytra with a distinct sculpture of scratches... 



8, striolatus. 



7 (6) Surface of elytra without sculpture of scratches. 



8 (9) Three or four sutural series of punctures very fine 3, natator. 



9 (8) Three or four sutural series of punctures distinct or fine. 



10 (13) Sides of elytra strongly rounded. 



11 (12) Elytra with a minute punctuation 7, colymbus. 



12 (11) Elytra without minute punctuation 4, suffriani. 



13 (10) Sides of elytra slightly rounded or straight. 



14 (15) External apical angle of elytra evident though obtuse.. .5, elongatus. 



* I may hero take the opportunity of saying that from observations I have made during 

 the last two years I have formed the opinion that the lateral lobes of the male jedeagus during 

 copula never enter the tube of the female. 



