THE OVIPOSITION RESPONSE OF INSECTS 5 



tropism during the breeding season. However, the recent experi- 

 ments of Sharma and Sen (72) appear to indicate, that dissolved 

 substances influence the oviposition response. 4 According to Hase 

 ($4), the degree of moisture has no effect on the egg-laying of 

 Habrobracon juglandis. 



LIGHT 



The character of the response of an insect to light has an im- 

 portant bearing on the kind of environment in which the eggs will 

 be laid. If the response is positive, oviposition will take place in a 

 well-lighted environment, unless, as sometimes happens, there is a 

 reversion of the normal heliotropism during the egg-laying period. 

 The opposite will be true of negatively heliotropic insects. 5 Grevil- 

 lius (30) states that light -plays an important part in the selection 

 of a place for oviposition by the brown-tail moth (Euproctis chry- 

 sorrhoea L.). An appreciable degree of darkness is essential for 

 heavy oviposition of the codling moth (Carpocapsa pomoneUa) 

 (1$). Dewitz (21) cites a number of references which indicate that 

 the European vine moths Oochylis (Olysia) ambiguellq Hiibn. and 

 Polychrosis botrana Schiff. select the shaded grape clusters for ovipo- 

 sition rather than those situated in strong sunlight. According to 

 Wardle (81), blow-flies seldom oviposit in food exposed to the sun's 

 rays, but they lay their eggs readily in the shade. The response to 

 light varies with the species of blow-fly concerned, Lucilia caesar L. 

 being more strongly heliotropic than Calliphora vomitoria L. Light 

 stimulates reproduction in the house fly (8), but is without effect 

 on the egg-laying responses of Drosophila mela.no g aster (1). 



Few observations upon the effect of color on oviposition appear 

 to have been made. The most important of these which the writer 

 has seen are embodied in the recent work of Knoll (46) on the rela- 

 tion of insects and flowers. The experiments were made on Macro- 

 glossv.m steTlataruia L., a European diurnal sphingid moth which 

 lays its eggs chiefly upon cruciferous plants of the genus Galium. 

 The oviposition flight of this moth is distinct from its flight when 

 in search of food. Knoll found that the gravid female made typical 

 oviposition flights to reflected light from chlorophyll solutions 

 (alcoholic solutions of crude chlorophyll and a- and ^-chlorophyll 

 from Galium plants) ; the moth reacted to the colored light and not 

 to the odor of the solutions. A number of artificial green and yellow 

 objects induced the oviposition flight, but in only one instance was 



egg deposited. To obtain the complete response, artificial flowers 

 made of green or yellow paper dipped in beeswax and each contain- 

 ing a drop of the press juice from plants of Galium moVugo L. were 

 I. Gravid moths flew to these objects, exhibiting the character- 

 istic oviposition flight and laid an egg on the under, side. This 

 result was often repeated; From these experiments, Knoll con- 



• In a recenl paper Crumb (Eat News, vol. ■"•"'. pp. 242 243* 1924) states that 

 tin nil: arising from water are strongly attractive to gravid female mosquitoes 



'i.uir.r pipimx />.). Experimentally, )h> Qnds dilute aq is solutions of. methane, hydro- 



sulphide, old yeast infusion, and stale urine i" be considerably more attractive 



than water alone. 



»Thus Diets and Zeteh (U. 8. Depti Agr. Bui. 885, ~>~> pp., 1920) Qnd ilia) the 



of the aleurodid Aleurocanthus wofjlutni Ashby are normally laid on the underside's 



of the leai ; females arc aegativcly heliotropic at the lime of oviposition, for 



a a leaf upon which a female Is ovipositing Is turned over so thai Hie lighl falls 



It, egg laying invariably ceases. 



