Februaey 22, 1907] 



SCIENCE 



311 



essential, there has often heen small provi- 

 sion for the searching preliminary investiga- 

 tions demanded by the situation. Studies of 

 the mining fields are numerous, some excellent 

 and thorough, but many have been entrusted 

 to men of little experience, whose results are 

 anything but satisfactory to those who try to 

 use them in actual practise. Almost in- 

 variably these reports ignore the accessible 

 but hardly wrought opinions of precedent 

 workers who have successfully applied their 

 observations in hundreds of instances. This 

 method has become so clearly recognized as a 

 * geological survey habit ' that one does not 

 now expect otherwise. The survey has grown 

 to such gigantic proportions that it can not 

 much longer contain itself. It would be better 

 to diminish its scope than to essay the suicidal 

 role of autocrat of American science. With a 

 better appreciation of the shortcomings of 

 some of its owji crew, whose hasty and super- 

 ficial work has caused them to guess that 

 they know more than they really have learned, 

 it is probable that the national bureau would 

 raise more enduring monuments than can be 

 possible under existing methods. Studies of 

 regional geology and monographic productions 

 at the hands of the recognized leaders in 

 geology have largely given place to ' omnium 

 gatherum,' publications of temporary and 

 chamber of commerce application. 



In conclusion, it does appear to one friend 

 of the survey that the value of the good will 

 and well-deserved support of the ablest workers 

 in geology is of more consequence than the 

 ephemeral and illusive prestige which may 

 enable the organization to ride rough shod 

 over all as supreme arbiter. Such greed of 

 power, if it really exists, as many have long 

 suspected, can not be long concealed. And 

 once it comes out in the open, its death-blow 

 is self-inflicted. The real fear, that thing of 

 which geologists derated by the survey are 

 actually afraid, is that the just outcome of 

 its energy and resources may not accrue to the 

 legitimate ends in view in its original estab- 

 lishment. This question transcends personal 

 considerations, and it certainly is involved to 

 some extent in the recently published discus- 



sion which is the text for this communica- 

 tion. 



Theo. B. Comstock 

 .Los Angeles, Cal., 

 January 12, 1907 



SPECIAL ARTICLES 

 VAEUTION IN MOSQUITO HABITS 



During the summer of 1906, a more sys- 

 tematic series of observations was made on 

 the salt-marsh area near the city of Elizabeth, 

 New Jersey, partly to determine the number 

 of broods, partly to ascertain the relative pro- 

 portion of 0. cantator and 0. solUciians, and 

 partly to learn more of their migrations. 



Generally speaking, we knew that the num- 

 ber of broods varied with the season, and that 

 it was largely a matter of tides and storms 

 as to how many there would be. We knew 

 also that in the southern part of New Jersey 

 C. solUcitans was the dominant species, 0. 

 cantator forming only a small minority early 

 in the season, and that cantator was dominant 

 in the northern section at least during the 

 early part of the summer. Concerning the 

 migrations we knew that they occurred; but 

 just how long they were continued and how 

 far they extended was yet a question. 



As early as April 19 there was a full brood 

 of larvse in the pools and these matured before 

 the end of the month. It formed brood I. of 

 the season, was almost all cantator, and the 

 adults left the meadow soon after hatching 

 and traveled inland along the valleys of the 

 Eahway and Elizabeth Eivers. On May 2 

 they were met with in great niunbers at Mill- 

 burn and covered the entire territory between 

 that and the marsh, a distance of about twelve 

 miles in a direct line. This migration was 

 not followed from the marsh directly. 



The II. brood was in the pools, already well 

 grown May 10 and reached the adult stage 

 May 15, 80 per cent, cantator, 20 per cent. 

 solUcitans. It was also a large brood, left 

 the meadow promptly in large proportion, and 

 was followed through the Elizabeth Valley to 

 Elizabeth, Aldene, Salem, Union, Springfield 

 and Maplewood. It also extended all along 

 the first ridge of the Orange Mountains and 

 reached Summit, a distance of fifteen miles 



