14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8l 



two adaptive conditions, which are distinguished morphologically by 

 different pigment deposits and that phototaxis depends on these 

 deposits ; that is, a dark deposit of pigment causes a dark adaptation 

 and negative phototaxis, while a light deposit brings about a light 

 adaptation and positive phototaxis. Lammert does not support this 

 hypothesis because he failed to find a migration of pigment in the 

 ocelli of certain insects, but his tests in which the ocelli were blackened 

 caused him to believe that lepidopterous larvae have two kinds of 

 photoreceptors — the ocelli and others lying in the body integument. 

 He believes, therefore, that these larvae have a skin sensitive to light. 

 The present writer's few experiments on this subject do not indicate 

 that codling-moth larvae have photoreceptors in their integument, and' 

 these larvae do not appear to be suitable material in which to search 

 for a migration of pigment in their ocelli. 



II. CHEMOTAXIS 



I. REVIEW OF LITERATURE 



Much was learned about chemotaxis long before the term chemo- 

 tropism was first applied to it. Among the earliest publications are 

 those of Fabre (20, pp. 179-216) and Forel (21, p. 76), who estab- 

 lished the fact that male moths are attracted from long distances to 

 their mates apparently by means of odors emitted by the females. 

 Mayer (58) in 1900 carried on tests with promethea moths and estab- 

 lished the fact beyond doubt that the males are attracted by emana- 

 tions from scent-producing organs of the females. Later Mayer and 

 Soule (59), Kellogg (27), Freiling (23), and others corroborated the 

 view that the emanations are emitted from scent-producing organs. 

 Priiffer (75, 76) more recently has supported this view in regard to 

 the gipsy moth. He assures us that the attraction between the sexes 

 is accomplished by means of aromatic substances which are secreted 

 by the females and the odors of which are perceived by the males. To 

 determine whether or not the attraction is similar to the radiation from 

 radioactive material, he confined the females in a lead cylinder which 

 would reduce the supposed radiation to a minimum and then allowed 

 the emanations from the cylinder to escape by means of a specially 

 constructed column of mercury. Using this apparatus he soon deter- 

 mined that the females thus confined attracted the males in the same 

 manner as do the females in the open air, but that the males were not 

 attracted when the females were confined in a hermetically sealed glass 

 container. Dead females were also able to attract males, but to a 

 lesser degree. Priiffer furthermore tells us that the radiation from a 



