42 ■ [.Tuiy, 



The full-fed larva is seven-eighths of an inch in length and stout in proportion, 

 tapering veiy little near the anal extremity ; the head black and glossy, and a glossy 

 hlackish-brown plate dorsally divided with a pale line is on the second segment, the 

 large shining spots of dark warm brown are darkest on the back, lighter brown and 

 smaller on the sides and belly, each spot having a fine dark hair, the shape and ar- 

 rangement of the spots quite as usual with many of the genus, the anal plate lightish 

 brown, the rest of the skin of the body is of a warm brown colour, melting gradually 

 into rather lighter, olivaceous, or ochreous-brown on the sides, the belly, and the hinder 

 segments, smooth but dull, yet showing distinctly through it a faintly darker dorsal 

 vessel and the pale tracheal thread besides other portions of the interior, the spiracles 

 round and black, each surrounded with a halo of pale ochreous. — Wm. Bucklee, 

 Emsworth : June \2th, 1879. 



Note on Gerris thoraclca. — In the " Termcszetrajzi Flizetek," 1878, Dr. Gr. v. 

 Horvath has given a sjnopsis of the Hungarian HebridtB, Veliidce, HydrohatidcB, 

 and HydrometridcE, in all fourteen species, all of them well known European forms ; 

 but he distinguishes Gerris thoracica, Schum., Flor, Fieb., Sahib., as distinct from 

 Hydrometra thoracica, H.-Schiiff., Doug. & Scott, giving this latter the name of 

 plebeius. Dr. Horvath properly lays the greatest stress as a specific character on the 

 form of the sixth segment of the abdomen of the (J in Gerris, as seen from the 

 under-side. In G. thoracica, H.-SchaiJ., D. & S., the lower edge of the sixth segment 

 beneath is emarginate, with a further deep rounded excision in the middle ; while in 

 G. thoracica, Schum., as interpreted by Dr. Horvath, it has only a single deep 

 rounded emargination, extending from side to side of the segment. A figure of each 

 is given, and I do not doubt for a moment that, with such a crucial character per- 

 taining to each, there are two distinct species, now first ably discriminated ; but it 

 does not appear to me, from the description of G. thoracica by Schummel (there is 

 no figure) that his species is represented by Horvath's Limnotrechus thoracicus. 

 Schummel (Ploteres, p. 47), unfortunately, says nothing pertaining to the under-side 

 of the sixth segment of the abdomen of the g , but " Oberseite des Hinterleibes . . . 

 Hinterrande des secshtes Hinterleibsglied schwacher ausgerandetals bei den vorigcn 

 Arten " {lactcstris), and this character, as respects the upper-side, is very slight, and 

 has no special importance. The antennae are said to be " merklich heller als bei der 

 Torigen Art (lacustris), hellbraun," which is true of our thoracica, but not of 

 Horvath's. 



Flor's //^orac/ra (Rhyn. Liv., i, 739) "Letztes abdominal Segment bei den $ 

 unten am Hinterrande mit einem regelmiissigen rundlichen Aussclinitt " appears by 

 these words to be Horvath's jAeheius, yet Flor cites H.-SchafPer's figure wliieh does 

 not accord. 



Fieber's thoracica (Eur. Hem., p. 108) has " Bauchendschiene tief schmal, oben 

 bogig, ausgeschnitten," and this character agrees with H.-Sch:iffer's figure (Wanz., 

 t. 299, fig. Z). Further, Fieber saw examples of our thoracica, and identified them 

 as his species. 



Sahlberg's thoracica (Notis. Fenn., xiv, 253) — " Mas : segmento ultimo ventrali 

 postice sat profunde rotundato-emarginato," may possibly be held to pass for Hor- 



