September 24, 1891] 



NATURE 



491 



appeared from time to time in the Report and Bulletin 

 of the United States Fish Commission, and upon the 

 Hand-books, &c., to the International Fisheries Ex- 

 hibition. These, with Grenville Murray's " The Oyster, 

 Where, How, When," &c. (1861 and 1863), Williams's 

 " Silvershell ; or the Adventures of an Oyster" (1856), 

 and Eyton's "History of the Oyster" (1858), are the 

 chief part of his stock-in-trade ; to which may be added 

 newspaper articles, reviews, extracts from popular natural 

 histories, &c. Besides these "authorities," some fifty 

 pages, largely taken from Gwyn Jefifreys's " Conchology," 

 deal with Brachiopoda (!), Anomiadae, Pectinidte, and 

 Ostreidae ; under the latter family there is an account of 

 Osirea cdulis, but none of Ostrea {Gryphced) angulata 

 and virginica, although the book does not profess to be 

 confined to the former species ; and about 212 pages are 

 occupied by reprints of Parliamentary papers of various 

 sorts. 



The only chapter in which we are at one with Mr. 

 Philpots is that in which an appeal is made to the 

 Government to take the " oyster question " seriously in 

 hand, though even here we cannot but regret the tone 

 in which he speaks of the Board of Trade. Unhappily, 

 however, there is no denying the fact that the inspectors 

 sent by the Board to report on oyster fisheries have often 

 been unfit for their task, and have, sometimes at any 

 rate, been freely fooled by interested parties, for want of a 

 little practical acquaintance with their subject. This has 

 been pointed out again and again, not only as regards 

 oyster fisheries, but also in connection with other fishery 

 questions ; but it cannot be pointed out too often. A 

 point to which Mr. Philpots should have drawn public 

 attention is that, if the proposition to move the London 

 drainage outfall to Foulness take effect, the best of the 

 few remaining grounds for breeding the almost extinct 

 " native " {settsu strictd) will in all probability be ruined. 



A book of a different calibre is that of Prof. Brooks. 

 It is avowedly merely an attempt to rouse the State of 

 Maryland to take such measures with regard to the oyster- 

 fisheries as can alone prevent their ruin, measures such 

 as some other States have already taken with marked 

 success. It is hardly necessary to say of Prof. Brooks 

 that his little book is a clear and accurate summary of 

 what is known about the American species, for few men 

 can speak with more authority on the subject. We can 

 only hope that the Legislature to which he appeals may 

 be more far-sighted than our own. Had the restrictions 

 which he advocates been laid on our English public beds 

 fifty years ago, the rare "native " might be almost as cheap 

 now as in those almost forgotten days when the market 

 was not yet flooded with French and Dutch produce 

 posing as the genuine article, and oyster grottos were 

 a familiar feature of the streets. 



THE DESTRUCTION OF MOSQUITOES. 

 Dragon-flies v. Mosquitoes. (New York : D. Appleton 

 and Company, 1890.) 



THE book before us consists of three prize essays 

 written in response to a circular issued in 1889 to 

 " The Working Entomologists of the Country," offering 

 certain prizes for essays containing original investigations 

 on methods for destroying the mosquito and the house-fly. 

 xNO. I 143, VOL. 44] 



The prizes were offered by Mr. R. H. Lamborn, whose 

 position as Director of the Lake Superior and Mississippi 

 Railway had caused him to spend a considerable time 

 encamped in the swampy forests which surround the 

 head of the great lake. Here he came into contact with 

 mosquitoes of the most irritating kind, and here he made 

 the interesting observations on their destruction by dragon- 

 flies which stimulated him to offer the above-mentioned 

 prizes. The lines laid down in the circular as to the 

 direction which the investigations should follow have 

 reference chiefly to the destruction of these insect pests 

 by dragon-flies. The competitors were also required to 

 examine which species of Odonata are best adapted for 

 the purpose, to investigate their habits, and the possible 

 methods of breeding them in large numbers. But al- 

 though this line of inquiry is suggested, the practical 

 object of the investigation is to determine whether it is 

 possible to diminish or extinguish the noxious Diptera, 

 and if so, by what means. 



The essay which gained the first prize is by Mrs. C. B. 

 Aaron, who gives a careful account of the habits and 

 life-history of both the Diptera in question, and of the 

 Odonata, and then considers the advisability and the 

 means of exterminating the former. The gravest charge 

 which is adduced against these Diptera, apart from the 

 irritation they cause, is that they act as carriers of such 

 parasites as Filaria, and possibly of some species of 

 Taenia, whilst they .undoubtedly serve to disseminate 

 Bacteria associated with certain infectious diseases. In 

 their favour it may, however, be said that they act as very 

 efficient scavengers, especially during the larval period 

 of their life-history ; and it is a very open question whether 

 the world would be much benefited by the total extinction 

 of the two genera Culex and Musca. Without attempt- 

 ing to decide this point, Mrs. Aaron proceeds to consider 

 the possibility and the cost of attempting their exter- 

 mination. 



The plan of pitting the dragon-fly against the gnat — a 

 plan similar to that which Prof. Riley has brought to 

 such a successful termination by encouraging the destruc- 

 tion of the orange scale, Icerya purchasi, by means of a 

 small beetle, the Vedalia cardinalis, imported from 

 Australia — is dismissed in a few words, for reasons 

 which are considered at greater length in the follow- 

 ing essays ; but several mechanical means are suggested, 

 the most promising and cheapest of which, in the case ot 

 the mosquito, is to spray with crude petroleum all collec- 

 tions of stagnant water which cannot be easily drained. 

 The oil forms a thin film on the surface of the water, and 

 effectually clogs the aperture of the breathing tubes as 

 soon as the larvae come to the surface, as they must do, 

 for air. 



The authors of the two remaining essays, Mr. Weeks 

 and Mr. BeutenmuUer, divide the second and third 

 prizes. The former commences his essay with a valuable 

 table, giving details of the time of appearance, of the 

 comparative voracity, and of the habitat of sixteen spe- 

 cies of dragon-fly found in the neighbourhood of New 

 York. From these, three are selected — Anax Junius, and 

 /Eschna constricta and heros—'aA the most likely to prove 

 destroyers of mosquitoes. When, however, the life-histories 

 of the opposed insects are compared, it becomes at once 

 evident that we must not trust to the Odonata to rid us of 



