June 3, 1910] 



SCIENCE 



869 



from such an author they command respect 

 and are sure to be widely quoted. On page 

 96 we find this assertion : 



In many of the more low-lying swampy coasts 

 crab-holes occur in enormous numbers in the 

 sandy soil, and in them are bred vast numbers 

 of mosquitoes. In fact they constitute the chief 

 nuisance in those houses which are situated near 

 the sea. 



The region in question is the tropical Amer- 

 ican littoral and the mosquitoes concerned are 

 the species of the genus Deinocerites and cer- 

 tain species of Culex, all of which breed ex- 

 clusively in crab-holes. I can myself testify 

 to the abundance of these mosquitoes in their 

 very restricted habitat, but must challenge the 

 learned author's statement that these mos- 

 quitoes are offensive in the manner he indi- 

 cates. Even where their breeding places are 

 in close proximity to houses these mosquitoes 

 do not enter, much less bite. Out of hundreds 

 of specimens, collected by ourselves and re- 

 ceived from correspondents, not one shows 

 traces of a blood-meal, nor have we been able 

 to observe that they are in the least attracted 

 to human beings. On the other hand, we have 

 female specimens of Culex extricator, one of 

 the crab-hole species, in which the abdomen, 

 distended with food, is of a pale amber color, 

 showing that the food taken was not vertebrate 

 blood. 



Such error, however, does no harm beyond 

 the useless expenditure entailed in the de- 

 struction of these inoffensive insects. In the 

 case of the control of the yellow-fever mos- 

 quito a wrong assumption becomes a more 

 serious question. The Sanitary Department 

 of the Isthmian Canal Commission deserves 

 great credit for its effective work in the con- 

 trol of this mosquito, and it is primarily the 

 thoroughness of this work that is making pos- 

 sible the rapid progress in the construction 

 of the Panama Canal. The report of the De- 

 partment of Sanitation for January, 1910, 

 gives brief data on the character of this work 

 and the gratifying results achieved in the 

 reduction of this mosquito. 



There can be no doubt that the yellow- 

 fever mosquito has been reduced below the 



danger-point within the Canal Zone, a thing 

 made easily possible by its habits of close as- 

 sociation with man. The implied claim, how- 

 ever, that this mosquito has been eradicated 

 from certain localities within the zone can 

 hardly be accepted upon the evidence pre- 

 sented. This consists of a faulty experiment 

 based upon the erroneous idea that the yellow- 

 fever mosquito normally lays its eggs upon the 

 surface of the water. 



At the native town in Gorgona wooden tubs 

 with water were put under the houses on Novem- 

 ber 6, 1909, and between that time and January 

 6, 1910, no Stegomyia eggs were deposited. Had 

 Stegomyia been present, eggs on the water surface 

 would probably have been found. 



The inference is that, because no larvse ap- 

 peared in the tubs and no eggs upon the sur- 

 face of the water, no yellow-fever mosquitoes 

 could be present in that locality. Such, how- 

 ever, is not the normal habit of oviposition of 

 this mosquito. The eggs are deposited out of 

 the water, at the edge of the water-film; here 

 the eggs remain until they are submerged, 

 when they promptly hatch. Eggs remaining 

 out of the water retain their vitality a long 

 time. In laboratory experiments eggs have 

 been kept dry as long as five months and, 

 when then submerged, produced larvse; under 

 favorable conditions out-of-doors it is to be 

 supposed that they will survive even longer. 

 Under the domestic arrangements of the more 

 primitive tropical homes the conditions are 

 ideal for the multiplication of this mosquito. 

 The water receptacles in common use, which 

 are the ordinary breeding places of this mos- 

 quito, are seldom, if ever, completely emptied; 

 water is added from time to time, and thus 

 whenever the water level is raised eggs can 

 hatch. It will be readily seen that in the ex- 

 periment quoted above eggs of the yellow-fever 

 mosquito might easily have been present but 

 could not have hatched, as the water in the 

 tubs remained undisturbed. 



Frederick Kjs-ab 



THE AMERICAX PHILOSOPHICAL SOCIETY 

 The general meeting of the American Philo- 

 sophical Society was held in the hall of the society, 

 Independence Square, Philadelphia, on Thursday, 



