OF WASHINGTON, VOLUME XIII, 1911. 175 



Systematically Dr. Lutz's papers are of greatest interest. 

 They demonstrate in a striking manner how very different 

 are the results when a group is studied intensively. In 

 the first paper Lutz did not depart from the traditional meth- 

 ods of the systematist and worked with the characters which 

 had been generally employed in the differentiation of the 

 species. In the second paper he takes into consideration the 

 early stages, particularly the pupae. These last he finds have 

 very definite and reliable characters and they show very clearly 

 that the number of species is much larger than was indicated 

 by the study of the imagos alone. In the first paper Lutz 

 was able to recognize only ten species and one variety; in the 

 second paper, it is true with a much larger material, he dif- 

 ferentiates no less than twenty-nine species. 



To the degree then, in which the material increased and the percep- 

 tion was sharpened, an increasing number of new species had to be 

 differentiated. The separation of many which are very similar is con- 

 nected with great difficulties and soon it became apparent that, in 

 consequence of slight variations and imperfections of some specimens, 

 a differentiation based upon size, color, and markings could not be 

 carried through. Rather, in searching for better anatomical differ- 

 ences, the microscope had to be constantly employed; hand-lenses 

 prove themselves inadequate, as strong magnification is often neces- 

 sary. Only through entirely disproportionate labor and countless 

 microscopic examinations was I able to obtain the present results, 

 still incomplete in some respects. 



The employment of the early stages in the differentiation of 

 species of Simulium is not new, but Dr. Lutz appears to be 

 the first one who has carried such studies through on a large 

 scale and in a logical and thorough manner. The following 

 elucidates Dr. Lutz's methods in working with the early 

 stages: 



Generally in waters which are suitable for breeding several species 

 commonly occur associated, which makes more difficult the differen- 

 tiation in the separate larva?. Although apparently the body colora- 

 tion of some species is constant throughout their entire development 

 and can be employed to a limited degree, one must take into consid- 

 eration that the filled alimentary canal shows through and that the 

 coloration of its contents is subject to great variation. The mental 

 plate shows but insignificant differences in most of the species, and 

 moreover in preparations but seldom assumes an entirely favorable 

 position. Therefore in determination one best holds to individuals 

 which are already near the last moult and show a dark spot on both 

 sides near the head, produced by the respiratory appendages of the 



