— 2 — 



lu this species & in a new Gerris [G. perseus, presently to be described), 

 I have encountered an amount of individuai variation in the proportions 

 of antennae, tarsi etc, for which I was entirely unprepared. 



Champion (1) separates his two species as follows : 



« Pronotum with a large triangular ochraceous patch on the anterior 

 « lobe ; antennae with joints » [segments] « 2 and 3 subequal in length; 

 « first genital segnient unidentate on the right side at the apex beneath 

 « in the cf. Unidentalus, n. sp. 



« Pronotum with a narrow ochraceous median line; antennae with 

 « joint » [segment] « 2 longer than 3; first genital segment bidentate on 

 « the right side at the apex in the cf. Bidentatus, n. sp. > 



The colour - characters, at least, here given are far from Constant, 

 and the species are evidently remarkably variable, so much so that until 

 an opportunity of examining a large series of both sexes occurs, I must 

 decline to do more than identify 3 of the 7 as P. bidentatus. The fol- 

 lowing table may, however, be of interest: 



antennal proportions 



(a) no 1 cf from Gualaquiza. 40 : 14 : 14 : 20 



antennae btoken 

 37 : 14 : ? ? 

 26 

 28 

 30 

 32 



{8) Nos 1, 2, 3 & 7 have a large triangular ochraceous patch on the 

 pronotum; Nos 4-6 have a somewhat narrow centrai stripe of the sanie 

 colour, on the pronotum. Nos 1-2 have 3 narrow, longitudinal, more or 

 less entire ochraceous stripes on the mesonotum, 4 & 5 have a short, 

 narrow stripe about the centre of the mesonotum, while 6 &1 are im- 

 maculate. 



Therefore, according to (a), ] & 7 ought to be unidentalus, 4-6 bi- 

 dentatus; according to (#), 1-3 & 7 ought to be unidentatus, 4-6 biden- 

 tatus. 



Nos 1 & 2, however, are unmistakably bidentatus, judging by the 

 structure of the genital segments; & I believe 3 to be the female of 

 the same species. Nos 4-7 I have labelled « Potamobates sp.?, probably 

 not bidentatus ». 



In the 5 9, the 6 segment of the connexivum is produced on both 

 sides considerably beyond the apex of the abdomen ; this prolongation 

 is rounded & blunt, and densely bairy, It is noteworthy that an appen- 



(1) Biologia Centr. Amer... Zoo)., Hemipt. Heteropt. II, pp. 154-5. PI. ix, 

 ngs 20-2. 



