1913] Observations on Chcetotaxy of Calliphorinae. 267 



As regards the wild flies captured it will be observed 

 that there are twice as many abnormal by reduction as there 

 are abnormal by addition. Too much importance should 

 not be attached to this fact, as it may be due toian error. In 

 a few cases there is reduction in the size of the bristle normally 

 present, but as a general thing there is no reduction unless the 

 bristle is entirely absent. On the other hand a very small 

 bristle is frequently added and it is more rarely the case that 

 a supernumerary bristle is of the full size. In looking over 

 a large number of flies rapidly, one would then have a tendency 

 to overlook the presence of the small additional bristle and 

 to record more reduction than addition in number. As these 

 flies were examined for the purpose of finding breeding material, 

 careful attention was not given to this matter and I am inclined 

 to consider the normal range of variation to be somewhat above 

 two per cent both in the direction of reduction and in the di- 

 rection of addition. This equality of variation in both directions 

 is seen in the progeny of normal females. In the progeny of 

 females abnormal by reduction and of females abnormal by 

 addition, the variation of the offspring is seen to tend in the 

 direction of the parental abnormality. 



A single female lacking three bristles, (3, 2, 1, 3), gave ten 

 males and twelve females of normal chaetotaxy. Three pairs 

 of these gave 215 normal flies, 23 abnormal by reduction, aind 3 

 abnormal by addition. A pair and a trio of these normals 

 gave in the third generation from the original female, 510 

 normals, 13 abnormal by reduction, and 24 abnormal by ad- 

 dition. This shows regression away from the abnormal and 

 suggests Galton's Law. 



Observations made on Lucilia sylvarum and caesar, and 

 on Calliphora erythrocephala, viridescens, and vomitoria lead me 

 to believe that these five species are analogous to Lucilia 

 sericata in the variation of their chaetotaxy. 



In conclusion I wish to express my thanks for suggestions 

 and criticism in the course of the work kindly offered by Pro- 

 fessor Wheeler, Professor Castle and Mr. Brues. 



