1929 ] 
Thelytoky in Scleroderma immigrans 
41 
THELYTOKY IN SCLERODERMA IMMIGRANS. 
By Clyde E. Keeler 
The Problem. 
For some time I have been interested in the presence and 
absence of wings in the Bethylid, Scleroderma, and the pos- 
sible mode of hereditary transmission for these conditions. 
We know that in this form apterous females and alate males 
are the rule, while winged females and wingless males occur 
rarely. In these facts we have evidence that the question is 
related in some fashion to sex determination. 
Among the Apidse and Bombidse, sex determination ap- 
pears to be capable of a quite simple explanation. A single 
complement of chromosomes bearing a certain ratio of male 
and female producing factors sets up a metabolic develop- 
mental rate characteristic of males. 
When a double complement is present, as in the fertilized 
ovum, a new ratio of metabolic tendencies is established and 
the result is a female. 1 
Nachtsheim postulates for the honeybee Apis mellifica a 
sex determination similar to the following : 
Results. 
9 = 2X + 2A = —4 + 2 - — 2 
$ = X + A — — 2 + 1 — — 1, 
where A ~ autoseme set — +1, and 
where X = sex chromosone jp — 2. 
The same method of analysis may be applied to other 
Hymenoptera such as the parasitic form Microbracon ( Habro- 
bracon) juglandis, where numerous investigators have found 
that virgin 9 $ produce males only. 
iUpon the same theory, by assigning hypothetical weights to sex 
chromosomes and autosomes, Bridges has been able to account for sex 
determination in normal Drosophila melanogaster as well as the sev- 
eral types of experimentally produced forms bearing aberrant chro- 
mosome numbers. Likewise, Goldschmidt account for intersexual forms 
of Limantria dispar produced by interracial crosses. 
