ZOOLOGY AND BOTANY, MICROSCOPY, ETC, 293 



Setae of Caterpillars as Aids in Classification.* — Stanley Black 

 Fracker has made an elaborate study of the chaetotaxy in Lepidopterons 

 larvge and its systematic value. The setal arrangement in every 

 segment of the body in larvae of the Lepidoptera has been derived from 

 the same ancestral type. This type includes twelve primary seta3, 

 which the author names after the Greek letters. The primary setse are 

 present in the first instar. They were established before the suborders 

 of Lepidoptera separated from each other, and possibly before the 

 separation of the order from other Holometabola. 



The ancestral plan has been modified in three ways, each being 

 more or less independent of the other two. 1. The prothorax shov?s a 

 tendency to retain the maximum number of seta ; this is a response to 

 the numerous sensory stimuli which this segment must transmit. 

 2. The mesothorax and metathorax sliow a partial reduction and 

 considerable modification in response to the necessary mobility of this 

 portion of the body. 3. The abdominal chtetotaxy has also been 

 reduced, but the seta? tend to retain their original typical position. 

 Segments 9 and 10 show specialized modifications of the setal 

 arrangement of segments 1 to 8. The setal arrangement in the chief 

 superfamilies is described. 



The second part of the memoir is a valuable systematic outline of 

 the families and genera, based on a study of the larvae. The chief 

 characters used are the head parts, the armature of the body, the 

 spiracles, and the prolegs. 



Experiments with Pomace Fly.-j- — Frank E. Lutz has experimented 

 on the influence of natural selection on Drosophila ampelophila. In 

 one set the flies were reared at a temperature kept rather close to 20° C, 

 and the adults were given water, but no food. In the other set the 

 flies were reared under normal, i.e. uncontrolled, temperature condi- 

 tions, and the adults were carefully fed, but not allowed to mate. The 

 duration of the embryonic periods in relation to the duration of the 

 adult life was studied, and two structural characters, the length of 

 the first posterior cell in the wing and the breadth of the wing, were 

 measured. The results were rather difficult, but they demonstrate the 

 reality of natural selection and its influence on mean, variability, and 

 correlation. 



The "Bar-eye" Mutant of Drosophila.|— C. Zeleny and E. W. 

 Mattoon have made experiments with a view to testing the germinal 

 uniformity as regards the distinguishing characteristic in a recent 

 mutant, the " bar-eye " race of Drosophila, in which the ommatidia are 

 reduced in number and the facets are restricted to a vertical band or 

 bar. The characteristic appeared in a single male in 1913; and the 

 whole race is descended from this individual. The race has undergone 

 no apparent change during the two years of its existence. Three 

 successive selections for high numbers of facets in the " bar-eve " race 



* Illinois Biol. Monographs, ii. (1915) pp. 1-169 (10 pis.), 

 t Bull. Amer. Museum Nat. Hist., xxxiv. (1915) pp. 605-24. 

 X Journ. Exper. Zool., xix. (1915) pp. 515-30 (5 figs.). 



