438 THE ZOOLOGIST. 



habit, and the result is a most useful guide to the subject of 

 which it treats, the value of which is enhanced by the original 

 illustrations so carefully drawn by Mr. A. K. Hammond. In 

 these days of rapid production of books, it is refreshing to take 

 up a volume which contains new figures expressly designed for it 

 — figures moreover which really serve their purpose by illus- 

 trating the author's meaning, instead of vexing the reader (as so 

 often happens) by not showing the very points on which some 

 elucidation is needed. 



The aquatic insects described in this volume have been 

 selected on no philosophical principles. They are merely such 

 as the author has happened to come across in his rambles by 

 pond and stream, or along the coast. But even this chance 

 collection of aquatic species yields interesting results when 

 studied from the right point of view. Prof. Miall describes 

 them in the following order: — Coleoptera, Diptera, Hymenoptera 

 (Ichneumons), Lepidoptera (Moths), Trichoptera (Caddis-flies), 

 Sialidse (Alder-flies), Perlidse (Stone-flies), Ephemeridse (May- 

 flies), Odonata (Dragon-flies), Ehynchota (Water Scorpions), 

 and Thysanura (Springtails). 



Especially interesting are his remarks on the " Degrees of 

 Adaptation to Aquatic Conditions," and on the " Wintering of 

 Aquatic Insects " (Introduction, pp. 11, 18). On the latter point 

 the author says : — 



" The common rule is, I think, that aquatic insects winter as larvae. 

 Nearly all aquatic Diptera, Dragon-flies, May-flies, Stone-flies, and Caddis- 

 flies do this. Occasionally, however, the winged individuals hybernate. 

 Examples are furnished by the Gnat, and one of the Dragon-flies (Lestes), 

 Fully armoured species, such as beetles and bugs, commonly pass the 

 winter in the winged state, burying themselves in the mud or in the earth 

 during unusually severe weather. Aquatic insects which have wintered as 

 larvse usually undergo transformation, and lay their eggs in the following 

 spring. From these eggs a summer generation proceeds, which becomes 

 ready for egg-laying ia September, and so the cycle comes round." 



In order to study the movements of a Caddis-worm (Phryganea 

 grandis) under something like normal conditions, Prof. Miall 

 suggested to a friend, Mr. T. H. Taylor, to supply a naked living 

 specimen with small plates of mica, in the hope that a trans- 

 parent case might be formed. This expectation was fully realised* 

 The creature formed a shapely and sufficiently transparent case 



