THE CANADIAN ENTOMOLOGIST. G3' 



The manner of using the tarsal hair tuft, it should be noticed, is very 

 difficult to observe satisfactorily, as the active bug moves its legs very 

 swiftly when swimming. At times, however, either through exhaustion 

 from long-continued rowing, or through weakness in partly drowned 

 individuals, they move the legs more slowly, so it is possible to see the 

 use of the hairs plainly, of which, when swimming fast, it is possible to get 

 only the merest glimpse. The ciliated hairs (figs. 3, 4 and 5), are extended 

 fan-wise (fig. 4), as may sometimes be seen in dried specimens. 



The tarsus is in contact with the water along its entire length, with 

 tiie slit vertical to the surface. When in this position the spread tuft of 

 hairs projects beneath into the water, and is a powerful auxiliary in 

 swimming. When swimming under water the hair tuft is also expanded, 

 and is uf great assistance. The necessity for an aid in swimming at the 

 surface is explained by the fact that Rhagovelia is to be found in the 

 swificst part of streams, where it may be seen zigzagging against the 

 current in little schools, which in June and July are made up principally 

 of the sexes in copulo. The very young nymphs betake themselves to 

 sheltered and still nooks along the banks. 



In cop. the ^ is above, as is usual with insects. When the ^ first 

 seizes the $ she endeavours to throw him off, and flings herself on her 

 back with the ^ under her. After a moment's struggle they right them- 

 selves. During this the $ sets the hind femora at right angles to his 

 body, bending the tibiae under, and, by means of them, holding the 9 's 

 second and third pair of legs straight and close to her body. Once he is 

 firmly on her, he releases this hold, but maintains his position by the 

 anterior legs, which clasp the 9 over the prothorax. He is not connected 

 with the $ continuously while on her back. To complete the act, he 

 seizes her as at first, by means of the hind legs. At other times he merely, 

 lies on her back quiescent, with his second and third pairs of legs extended,' 

 but not touching the surface. As long as the <^ is on her the % does all. 

 the swimming. 



It is known that Rhagovelia swims freely under water, and to my 

 disgust the individuals I had persisted in diving. They were taken in the, 

 afternoon, and being put in an aquarium, when night came, they took, to 

 diving. By II p.m. they v/ere all actively swimming under wat€r, T|o; 

 penetrate the surface film they put the head down at the surface, and, by 

 means of a few vigorous swimming-strokes with the intermediates, they 

 force themselves under. When under water they swim about freely and 

 rapidly by means of the intermediates, the tarsal swimming-tuft being fully 



