THE OVIPOSITION RESPONSE OF INSECTS 3D 
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.t According to Hase 
(34), the degree of moisture has no effect on the ego-laying of 
| Habrobracon juglandis. 
| LIGHT 
The character of the response of an insect to hght 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. Grevil- 
lius (30) states that light plays an important part in the selection 
of a place for oviposition by the brown-tail moth (Zuproctis chry- 
sorrhoea L.). An appreciable degree of darkness is essential for 
heavy oviposition of the codling moth (Carpocapsa pomonella) 
(42). Dewitz (27) cites a number of references which indicate that 
the European vine moths Cochylis (Clysia) ambiguella 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 paar of Drosophila melanogaster Cie 
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 fiowers. The experiments were made on J/acro- 
glossum stellatarum L., a European diurnal sphingid moth which 
lays its eggs chiefly upon cruciterous plants of the genus Galium. 
The oviposition flight of this moth is distinct from its flight when 
in search of food. Jnoll found that the gravid female made typical 
oviposition flights to reflected light from chlorophy 1] solutions 
(alcoholic solutions of crude chlor ‘ophyll and g- and $-chlorophyll 
from Galium plants) ; the moth reacted to the colored ii eht 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 
an 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 Galiwm moliugo LL. were 
used. 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- 
4In a. recent paper Crumb (Ent. News, vol. 35, pp. 242-243, 1924) states that 
certain odors arising from water are strongly attractive to gravid female mosquitoes 
(Culex pipiens L.). Experimentally, he finds dilute aqueous solutions of methane, hydro- 
gen sulphide, old yeast infusion, and stale urine to be considerably more attractive 
than water alone. 
5Thus Dietz and Zetek (U. S. Dept. Agr. Bul. 885, 55 pp., 1920) find that the 
eggs of the aleurodid Aleurocanthus woglumi Ashby are normally laid on the undersides 
of the leaves. The females are negatively heliotropic at the time of oviposition, for 
when a leaf upon which a female is ovipositing is turned over so that the light falls 
directly upon it, egg laying invariably ceases. 
