March 24, 1911] 



SCIENCE 



455 



The School of Engineering at the Univer- 

 sity of Pittsburgh, announces that Mr. Morris 

 Knowles, C.E., will take charge of the course 

 in sanitary engineering and public health. 

 This course will be developed in cooperation 

 with the medical school of the university and 

 the departments of health of the city and 

 state. The students will have a year's prac- 

 tical work along this line during their four 

 years' course. 



The board of trustees of the University of 

 Illinois in its annual meeting on March 14, 

 made the following appointments and promo- 

 tions: George AKred Goodenough, associate 

 professor of mechanical engineering, of the 

 university was promoted to be professor of 

 thermodynamics. Professor Charles Euss 

 Eichards, dean of the College of Engineering, 

 University of Nebraska, professor of mechan- 

 ical engineering in charge of the department. 

 Professor Eiehards succeeds, as head of the 

 department, Professor L. P. Breckenridge, 

 who two years ago relinquished his office to 

 take up work at Tale University. Mr. Burt 

 E. Eickards, of Columbus, Ohio, who has been 

 for some three years chief of the laboratories 

 of the Ohio State Board of Health, was ap- 

 pointed associate professor of municipal and 

 sanitary dairying in the Agricultural College. 



DISCUSSION AND CORRESPONDENCE 



■J LARVAL SPECIES 



In his recent review of Theobald's last vol- 

 ume on the mosquitoes Dr. E. P. Felt em- 

 phatically condemns the founding of species, 

 or of a classification, on larval characters.^ 

 Dr. Felt has a right to his opinion, but his 

 remarks are so incomplete that they do not 

 fairly present the question at issue. In the 

 case of the Culicidaa, as in the many others 

 that might be cited, there were causes which 

 led logically to such a course. First of these 

 was the fact that certain species of mosquitoes 

 could not be distinguished in the imago state, 

 while they showed very marked diilerences in 

 the larval condition. This led naturally to 

 the founding of species on the early stages 

 and Dr. Felt himself was the first to take this 



1 Science, N. S., Vol. XXXIII., pp. 150-151. 



step. He has been amply justified by the fact 

 that, in spite of diligent study with abundant 

 material, no tangible characters for separating 

 the imagos have been found. It should be 

 added that a study of the male genitalia has 

 revealed corresponding differences, equally 

 marked with those of the larvse. There can 

 therefore be no question that the species indi- 

 cated on larval characters really exist in na- 

 ture. Since then a considerable number of 

 species have come to light which are only 

 separable on characters of larvse and male 

 genitalia. 



Under such circumstances two courses are 

 open to the systematist who will not recognize 

 larval characters, neither of which, in our 

 opinion, is scientific. The most convenient is 

 to ignore the true condition and adhere to the 

 concept of species on the basis of well-marked 

 differences in the imagos ; the other is to admit 

 the species indicated by the larvas and draw 

 up descriptions from the indistinguishable 

 imagos. To designate, as specific, individual 

 differences due to variation, as Theobald has 

 done in the case of Aedes fitcMi, A. abfitchii 

 and A. suhcantans,' only obscures the subject. 

 We do not advocate the founding of species 

 on larval characters as a general practise and 

 we think that Dr. Felt expresses needless 

 alarm on this account. Under the special 

 conditions indicated above and in similar 

 cases we not only consider the founding of 

 species on larval characters justified, but un- 

 avoidable. Furthermore, if the mosquitoes 

 are considered from an economic standpoint 

 (and we are constantly told that this is the 

 primary reason for their study) a knowledge 

 of the larvEB is fully as important as that of 

 the imagos. 



But, Dr. Felt's criticism in his approval of 

 Theobald's position is mainly aimed at our 

 paper on the classification of the mosquitoes 

 by larval characters.' He chooses to ignore 

 the fact that we have since published a classi- 

 fication of the imagos, which, in the main, is 



-"Monogr. Culieidaj," Vol. 4, 1907, pp. 319,321. 



' " The LarvsB of Culieidje Classified as Inde- 

 pendent Organisms," Journ. N. Y. Entom. Soc, 

 Vol. 14, 1906, pp. 169-230, pi. 4-16. 



