272 THE ENTOMOLOGIST. 



are laid in May or June, and again in August or September. Conse- 

 quently there are two broods a year, and this seems to be the case 

 with P. germanica in Britain — sometimes, at any rate. The winter 

 is passed by the larva, in its last larval stage, in the burrow. 



Two excellent plates illustrate the earlier stages of the insect. 

 Miyake concludes his paper with the description of a subspecies, 

 nigra, of which apparently P. nipponensis and P. brachijpennis are 

 only other forms. ' W.J.Lucas. 



The North American Dragonflies of the Genus JEshna (University of 

 Toronto Studies, Biological Series). By E. M. Walker, B.A., 

 M.B. Pp. 213. Toronto, 1912. 



There has for a long time been a difference of opinion as to the 

 spelling of the name of this genus. lEschna is generally used in 

 Europe, and will probably continue to be used, especially as the 

 change to JEshna would introduce a difficulty in connection with 

 compounds such as Amphiaschna. This matter is, however, un- 

 important in face of the excellent monograph of the North American 

 members of the genus which Mr. Walker has produced. 



Throughout the work it is very obvious that our author is 

 an experienced field naturalist, and we are therefore not surprised to 

 find some fifty-six pages devoted to the biology and bionomics of the 

 American iEschnas. The entomologist, therefore, who takes a com- 

 prehensive view of his science (although he may not study dragon- 

 flies in particular) will wish to inspect this monograph. Following 

 these introductory pages are full, elaborate keys for the identification 

 of both males and females, and in addition such nymphs as are 

 known to science. Each species is then most fully treated, and the 

 distribution, habits, relationships, and so on, are not forgotten. 



Of North American JEschnas, there are sixteen species, according 

 to Walker, with four forms to IE. interrupta, and two to IE. umbrosa. 

 In Europe there are nine, while in Britain we have six. Of these 

 one species, IE. juncea, is common to Europe and North America, 

 this being a British species also. 



After a list of works cited, we come to the plates, twenty-eight in 

 number, six illustrating the abdomens of the imagines being coloured. 

 All are excellent. Though we possess but six iEschnas to the North 

 American sixteen, yet it is evident from the plates alone that there is 

 much less diversity among the American species than amongst our 

 own. Across the Atlantic there are none that resemble our IE. 

 grandis and IE. isosceles. 



Mr. Walker mentions an interesting observation of M. constricta 

 ovipositing in the stem of a sweet-flag (Acorus calamus) some two 

 and a half feet above the water. He thinks the eggs fall out as the 

 plant withers. On one occasion I saw a Platycnemis pennipes to all 

 appearance ovipositing in the stem of a yellow water-lily flower some 

 inches above the surface. If eggs were laid, they would later have 

 been brought below the surface, when, after flowering, the fruit came 

 down to water-level, as is the custom with this plant. Is it not 

 necessary for the eggs to remain moist ? W T Lucas 



