JANTJAEY 24, 1913] 



SCIENCE 



147 



all diiferently. It is interest and enthusiasm 

 we are after in medicine — not the dead routine 

 of a schedule. We need very badly pedagogic 

 vitality. One man may make, or be able to 

 make, twice the progress of another in a cer- 

 tain subject. Why tie him to the class sched- 

 ule? Why not take him into your own labora- 

 tory, for his class periods, give him an assign- 

 ment of special work, and talk it all over with 

 him. It is 'a stimulus to students and teach- 

 ers. It makes for progress in the student, not 

 for stagnation. It widens his perspective, and 

 not infrequently wakes the teacher. A sched- 

 ule is made for the general mediocrity, and in 

 its planning visibility is a prime necessity. 

 Paul G. Woollet, 



Dean 

 College of Medicine, 



University op Cincinnati 



a proposal for the control of certain 

 mosquitoes 



With the discovery that a number of dis- 

 eases are transmitted solely by certain mos- 

 quitoes the control of these insects has become 

 an important problem. But for successful 

 control work exact knowledge of the species 

 involved and of their habits is essential. 

 Until a decade ago Reaumur's admirable pres- 

 entation of the life history of the common 

 house mosquito (Culex pipiens L.) has been 

 almost universally considered applicable to 

 mosquitoes in general. Nothing was known 

 of the specialization of habits in the different 

 species and it was generally supposed that in 

 temperate regions all mosquitoes hibernated 

 in the adult female condition, to deposit eggs 

 and start a new generation with the return 

 of warm weather. Students of the group now 

 know that there is great diversification of hab- 

 its and that the old generalizations apply to 

 but a very small proportion of the many 

 species of mosquitoes. Nevertheless, the old 

 ideas persist with many and are still dissem- 

 inated in well-meant attempts to popularize 

 the subject. One often encounters recommen- 

 dations for mosquito-control based upon these 

 old ideas and leading to failure and useless 

 expenditure. 



The greatest misconception is that swamps 

 and bodies of stagnant water in general con- 

 tinue to produce mosquitoes in quantities 

 throughout the warm months and that to re- 

 duce mosquitoes it is only necessary to oil or 

 petrolize such places at sufficiently frequent 

 intervals. In fact the bulk of the mosquito 

 population of our northern woods and swamps 

 (and this is true of Eurasia as well as of 

 North America) is derived from larvae which 

 develop in the snow-water of early spring. 

 During a short period all the lesser bodies of 

 water swarm with mosquito-larvae, to shortly 

 become, for the remainder of the season, prac- 

 tically barren. The larvae hatch from eggs 

 which were deposited the previous summer on 

 leaves or rubbish in depressions of the ground. 

 There is but a single brood and the larval 

 period is short; the female imagos are long- 

 lived (weeks and even months) and the egg- 

 stage lasts through the winter to the following 

 spring. 



The species of mosquito which conform to 

 the old idea, hibernating as female imagos and 

 producing a series of generations during warm 

 weather, are, in temperate regions, few in 

 number, and their control is comparatively a 

 simple matter. It is true that in villages, 

 towns and cities even in the northern states 

 these Culex mosquitoes will breed in tin cans 

 and bottles on waste lots, in cesspools, rain- 

 water tanks, rainwater barrels and other re- 

 ceptacles, and cause much annoyance. A 

 community wishing to rid itseK of such mos- 

 quitoes must carry on a warfare directed 

 against these particular mosquitoes. 



The species hibernating as eggs and devel- 

 oping in early spring (mostly belonging to the 

 genus Aedes, sense of Dyar and Knab) are, on 

 the contrary, numerous in species and individ- 

 uals, and under suitable conditions very an- 

 noying. Their control, through destruction 

 of the larvEe, is a difficult matter. Petroliza- 

 tion, the method most recommended, must be 

 carried out at just the right time. As the 

 larvae occur in practically all the numerous 

 pools of snow-water scattered through woods 

 and fields, operations will have to be very 

 extensive to bring appreciable results. More- 



