INSECT VAUIETY. 131 



several couples were quarrelling at the time, it might have pro- 

 ceeded from a couple nearer the top/' Herr W. L. Schmidt, 

 having taken a very rich catch of this beetle, detected the 

 proportionately loud creaking was produced each time the insect 

 raised the last segment of the abdomen and pushed it under the 

 wing-covers, in and out. Applying himself to account for this 

 motion, he was led to the discovery of a ridge {limce), com- 

 mencing near the sutural edge of the elytra, at about one-third 

 its length from the extremity, and from thence running obliquely 

 to the apex, which as it approaches it dilates. On examining 

 this ridge with a glass, he noticed closely placed, deep cross 

 furrows, and these gave out a note similar to the cry of the beetle 

 when scratched by a quill pen. The active organ in the creaking 

 is an extremely sharp, thin, and prominent horny edge, that 

 surrounds the last abdominal segment. Some other Water Beetles, 

 as Acilius 'sulcatus, L., both male and female, and the male of 

 Colymhetes fuscus, L., stridulate in the same fashion, producing a 

 humming sound. 



The Philhydrida present a transition from the aqueous to the 

 terrestrial, include minute beetles, aquatic, or merely as their 

 name denotes, fond of the vicinity of the calm and whirl of the 

 stream and pond. As the mouths of these are deficient in a 

 pair of palpi, their powers of seizure are less, and they have not 

 the rapacity of the first two groups. The Danish coleopterist. 

 Professor Schjodte, in noticing the habits of the minute 

 species of Bleclms, Heterocerus, and Di/scJiirius, says : — 

 " The connection between these three genera is not of a 

 systematic character, for they belong to widely different 

 families, but they are closely connected by their habits, living 

 together as they do on the shores of fresh and salt waters, where 

 they excavate tunnels and galleries, which betray their presence 

 on the surface by small heaj)s of earth, like diminutive molehills. 

 The short elytras, Bledius, and small Heteroceri, are not seen 

 about in the day-time, but come out of their habitations on warm 

 summer evenings after sunset, flying in numbers near the sur- 

 face of the water. Herr Erichson, having possibly reason to 

 suppose the tiny kinds of Heterocerus produced an airy creak, sub- 

 mitted some to a magnifying glass, and discovered the existence 

 of a peculiar arched ridge on each side of the first ventral arc 

 J % 



