GUIDE TO THE STUDY OF BRITISH WATERBUGS. 231 



ingly like the common European Venilia maculata, L. in size and 

 colouring. It occurred in Costa Kica, but was scarce. 



Pytlionides sallei, Feld. — This is the most interesting of the 

 one hundred and sixty species of Heperid^ obtained. My 

 specimen was taken at Escuintla, Guatemala, and one was seen 

 at Cuautla, Mexico; as it is recorded from Eastern Peru, its 

 range would seem to be very extensive. 



Thysania agrippina, L. — This giant Noctuid, one specimen of 

 which is ten inches in expanse, was captured at Old Guatemala, 

 a locality which must be very near the most northern limit of its 

 range. 



In conclusion I may remark that the comparative scarcity of 

 Lepidoptera at moderately high elevations was very striking, and 

 difficult to explain. At upwards of 5000 ft. very few species 

 were to be found, whilst above 7000 ft. a few small LycaDnidse 

 alone were met with, despite the fact that the vegetation is 

 luxuriant up to an elevation of above 10,000 ft. Neither the 

 Alpine species of the Neoarctic region, nor the Andean forms of 

 Colombia and Peru, have more than a few isolated representa- 

 tives in Central America. 



June 24th, 1905. 



A GUIDE TO THE STUDY OP BRITISH WATERBUGS 

 (AQUATIC HEMIPTERA OR RHYNCHOTA). 



By G. W. Kirkaldy. 



(Continued from p. 178.) 



The Corixidae form a well-marked group, which has sprung, 

 apparently, from a Naucoroid stem. They are characterized by 

 the narrow, somewhat flattened form, the obscurely segmented 

 rostrum,* modified anterior legs, &c. The head is strongly 

 deflexed, and varies in form in the sexes, except in Micronecta. 

 The pronotum is usually large, the anterior margin being more 

 or less concealed by the posterior margin of the vertex, while 

 its posterior margin conceals all but a very small part of the 



"-•= Bornev (" Zur Systematik der Hexapoden," 1904, in Zool. Anzeiger, 

 xxvii. 522) has instituted a special suborder — SandaUorrhyncha — for the 

 Corixidae, on account of the short obscurely segmented rostrum, deeming it 

 a link between the Homoptera and the Heteroptera. This is far from correct, 

 the Corixidae being, as Handlirsch properly points out (" Zur Systematik der 

 Hexapoden," 1904, in Zool. Anzeiger, xxvii. 746), a terminus of one of the 

 heteropteral lines. The rostrum is merely a protecting sheath for the 

 piercing and sucking organs, and has no functions, apparently, as a pump. 

 In certain terrestrial forms with flexible rostrum (Miridse, &c.) the living 

 bug may be seen bending its rostrum at the junction of the second and third 

 segments, at more or less of an acute or obtuse angle, according as the bug 

 desires to pierce more or less deeply into the food substance. 



