30 ENTOMOLOGICAL NEWS [xxxii, '21 



450.) Wolff, M. Bermerkungen uber die p Porizoninen-gattungen 

 Isurgtis und Tersilochus. Ill, 1919. A, 3, 139-56. 



Cushman, R. A. North American ichneumon-flics, new and de- 

 scribed, with taxonomic and nomenclatorial notes. 50, Iviii, 251-92. 

 MacGillivray, A. D. New saw-flics from Maine and New York. 4, 

 lii, 233-6. 



A NEW STUDY OF THE ECONOMIC VALUE OK DRAGONFLIES. 



Under the heading "Dragonflies and Damselflies in relation to pond 

 fish culture, with a list of those found near Fairport, Iowa," Professor 

 C. B. Wilson has published in the Bulletin of the U. S. Bureau of 

 Fisheries (Vol. 36, pp. 185-264) an interesting and valuable contri- 

 bution to knowledge of the biology of this group of insects. His 

 paper deals with the fundamentals of animal economy food, enemies 

 and conditions for reproduction. His material was obtained in and 

 about the ponds of the Fisheries Biological Station at Fairport, a 

 description of which is first given. Then the relative abundance of the 

 dragonflies found there in the summer, as definitely determined hy 

 counts of cast nymphal skins left at emergence, is given. These counts 

 show the skimmer, Libcllula htctnosa to be by far the most numerous, 

 with Erythemis simpUcicoHis second. Then the food of 250 nymphs 

 determined by examination of the contents of the alimentary canal, 

 is given. These records corroborate and extend the observations of 

 Miss Mary B. Lyon at Ithaca (Entomological News 26: 1-15, 1019) and 

 of Alfred Warren in Hawaii (Coll. of Hawaii Hull. No. 3, 1915), and 

 show that while there are differences in diet according to species and 

 size of individuals, the staple foods in these ponds are small snails of 

 the genera Physa and Planorbis, mayfly nymphs and crustaceans. All 

 the forms studied eat also dragonfly nymphs smaller than themselves. 

 and some are cannibals, eating the young of their own species. Two 

 later sections of the paper discuss Odonata as food for fishes, sum- 

 marize the results of past studies on wild fishes and add some new data. 



There are numerous figures that are, on the whole, well executed : 

 but the cleft middle lobe, shown in the labium of B. simplicicolUs in 

 figure 13, is surely an artifact or an error. The occipital tubercules 

 shown so prominently in the new hatched nymph of Epicorditlia 

 princeps. usually present, though small, on newly hatched nymphs 

 of Libelluline dragonflies, are not shown on any of the half do/en 

 figures representing new hatched nymphs of that subfamily.* 



Under "experiments in hatching eggs," half a dozen spec it- of 



*If the grave error charged against Needham & Lloyd of publish 

 ing (on page 389 of their Life of Inland li\ttcrx') a photograph with- 

 out stating whether the photograph was taken under natural or under 

 artificial conditions, may be helped thereby, the reviewer will here 

 state that the two were photographed as found in nature, and the 

 nymph was not starved into eating the fish 



