THE BRITISH HEMIPTERA. 13 



But Mr. Dale once took three pairs winged in his own pond, 

 where the water is nearly stagnant ; into this pond a few days 

 previously he had put three pairs of apterous specimens 

 taken fi'om a stream, and although he cannot prove they 

 were the same he afterwards caught, he believes they were, as 

 he never found the species in his pond before or since." 



Of the genus Velia we read, at p. 571, " the insects of this 

 genus live gregariously on the surface of water, where, as 

 Schummel observes, they look like spiders, and ihey move 

 rapidly about by little leaps." 



And at p. 587 we read that " the NotonectcE swim very 

 rapidly, with the back downwards, using their hind legs like 

 oars, whence their name of * boat-flies.' Their rostrum is 

 capable of inflicting a painful wound in the hands of those 

 who take hold of them without due care." It is observed 

 also of the pygmy genus Plea, that, "like Notonectaj it 

 swims with the back downwards." 



In the genus Corixo, of which there are no less than 18 

 species described in this volume (by far the largest number 

 of species in any one genus), not less than eight, we observe, 

 have been detected by Mr. G. R. Crotch in the Cambridge 

 Fens, which we apprehend is an indication that, if other 

 districts wei-e explored with equal care, many other additions 

 might be made to the genus. 



The plates are 21 in number, and are in Mr. Robinson's 

 best style ; they are a model of what entomological plates 

 ought to be. The first plate is devoted to the general struc- 

 ture, and if this plate be studied with the aid of the introduc- 

 tory chapter, pp. 1 — 5, the veriest tyro will find no difficulty 

 in applying the proper names to the various parts of a 

 Heteropterous insect. There are magnified views of the 

 upper and underside of an insect of one of the most typical 



