R. G. Harris.
Sex of Adult Cecidomyidae (Oligarces sp.) Arising from Larvae Produced by Paedogenesis.
Psyche 31(3-4):148-154, 1924.

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148 Psyche [June-August
SEX OF ADULT CECIDOMYIDB (OLIGARCES sp.) ARISING FROM LARVA3 PRODUCED
BY PBDOGENESIS.
REGINALD G. HARRIS.
Brown University.
Communicated from the Biological Laboratory, Cob Harbor, Long Island.
d Spring
The question of the sex of adult forms arising from par- thenogenetically and psedogenetically produced individuals has called forth some debate and speculation, often in the absence of suitable date. Sturtevant (1923) summarized the evidence then available concerning some of the Chironomidse and Ceci- domyidse in the following statements.
'Parthenogenesis has been described in the Chironomid genera Chironomus, Corynoneura, and Tanytarsus by Grimm (1870) Johannsen (1912), Goetghebuer (1913), Edwards (1919) and others. Eggs are produced in some cases by the larvae, in others by the pupae, and in still others by the imagines. In all cases in which imagines have been produced by parthenogenetic (including psedogenetic) lines, these have been females and have bred parthenogenetically if at all. Males are known to occur in these genera, and in one case even in a species that reproduces parthenogenetically; but in no case are males reported as arising from larva? known to have been produced by parthenogenesis. "The first case of parthenogenesis recorded among the Diptera was that of the Cicidomyiid, Miastor, discovered by Wagner (1863). In this case it is the larvae that reproduce par- thenogenetically. Imagines are often produced, but when they do appear both sexes are found (Meinert 1864, Wagner 1865, Kahle 1908). Kahle states that there is a significant excess of females, and Felt (1911) describes only the female, though he does not state that males were absent. It is not known whether the imagines breed at all, or not; Kahle states that he did not



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19241 Sex of Adult Cecidomyidce (Oligarces sp.) 149 observe copulation. It does not appear to have been entirely proven that the males arise from larvse that have been produced by psedogenesis, though most students of Miastor have ap- parently taken this for granted without making cultures from isolated larvcfc."
J
This latter objection has been removed by the writer, who, in using Miastor and Oligarces as material for experimental work, has, for some time, made cultures from isolated larvae, and main- tained them on art>ificial culture media. The methods, and some of the results of this work have been reported already. A suitable method of cultivation of Miastor metraloas on an ar- tificial culture medium was found (Harris' 1923, 1, 2). This method was improved and simplified in later work on Oligarces (Harris 1923, 3). Both of these methods remove the possibility of contamination of the culture by other larvae than those under observation. The data contained in this report are taken largely from the work on Oligarces.
Cultures of psedogenetic larvae of Oligarces, if kept in dark- ness at a suitable temperature, are easily maintained in Petri dishes in the laboratory, on the following culture medium; 0.5 per cent malt extract, 2 per cent agar agar, 9'7.5 per cent water. Thus the difficulty of making cultures from isolated larvae is greatly lessened. It may be said, however, that in making cul- tures from isolated paed~genet~ic larvae it is advisable to take a mother larva containing nearly full term embryos, as cultures made from an individual larva are more liable to be unsuccessfu~ than those in which several larvae are present. By using a mother larva containing embryos about to be born, ode is assured of starting a culture from an isolated larva, while, at the same time, providing the new colony, almost immediately, with several young larvae with which to carry on the strain. Similar results may be obtained by freeing full term embryos from the skin of the mother larva by dissection in water on a microscope slide, and then transferring these young of an isolated mother to a new culture. Both of the foregoing methods are recommended as time-saving, and as productive of well es- tablished colonies.




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Psyche
[June-August
I have previously reported (Harris 1923, 3, 1924, 1) that pupae and adults can be produced at will in the laboratory by ,
maint,aining a crowded condition in the previous generation. Pupae and adults produced in this way were used as material for the present study. These pupae and adults arose in all cases from psedogenetic stock, taken in nature, and maintained on ,
artificial culture medium in the laboratory. In no case are
data given on cultures which did not pass at least one psedo- genetic generation in the laboratory previous to the appearance of pupse-larvse. In some cases the data concern mass cultures. in other cases cultures which originated from an isolated psedo- genetic mother larva.
It was found that the pupae and adults which appeared in mass cultures, made from psedogenetic larvse of psedogenetic origin, were as likely to be males as females. Thus in cultures Biz and Cis of 28 tfupse? chosen at random and sexed, 18 were males and 10 were females.
In culture M79, of 2 adults, 1 was a
male, 1 a female. A similar sex ratio was observed in culture MNO 340.
All of these cultures were originally made of varying numbers of isolated psedogenetic larvae of known psedogenetic origin. Thus it is clear that male as well as femde pupae and adults arise from larvae which have been produced by pssdogenesis. Male pupse, when dissected, were found to contain large numbers of sperms in the gonads, while ib the female usually about four or five large eggs are visible in living specimens. It seems likely then that both males and females are functionally as well as mor- phologically different. Up to the present time, however, I have not attempted to obtain progeny from adults, and so cannot state whether or not copulation can be easily obtained in the laboratory.
Whether the number of males will be equal to or greater than the number of females, or vice versa, in a given culture, was shown to depend upon .the type of stock which was selected in making the cultures, for it appears that in the same colony in nature certain paedogenetic larvae belong to male producing strains, dhile other larvae constitute female producing strains.



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19241 Sex of Adult Cecidomyidoe (Oligarces sp.) 15 1 Thus in the eighth generation of material originally taken from a single colony in nature, and maintained in t'he Laboratory by the means already described, individual 4XX was segregated and transferred to a fresh culture made of the standard medium. In the third filial generation pupae and adults appeared as a result of crowding in the previous generation (Fs). All of these pupae and adults, 38 in number, which were sexed were females. In the fifth filial generation of the same strain, pupae and adults again appeared under similar conditions, in three separate cultures. In culture M222, 26 pupae and adults were sexed. All were females. This was equally true for the 23 individuals sexed in culture M223, and for the 59 individuals sexed in culture M224. Thus all of the 108 F5 pupae and adults which were sexed were females. It is apparent that the progenitor of this strain, individual 4XX, must have beloved to a female- producing strain, since all of the pupa and adults produced by her offspring, both in the Fg and F5 generations, were females. Conversely, at the same time, and under similar conditions, individuals of other strains of known paedogenetic origin, gave rise to male pupae and imagines only. Thus in culture MN320 5 pupse appeared; all were males.
Similarly in culture COz3
five adults arose fro,m an isolated psedogenetic mother of known psedogenetic origin. These five adults were males. Male pupae of Miastor metraloas appeared in a colony, maintained in decayed birch, wood in the laboratory in Paris (Prof. Maurice Caullery, Director) under crowded conditions in a tin box. Though these did not arise from larvae all of which had been carefully segregated and examined, the fact that they appeared some two months after the material had been trans- ferred to the laboratory makes it more than probable that they were produced by larvae which had arisen psedogenetically from psedogenetic larvae originally present in the material. This conclusion is further supported by the fact that all paedogenetic larvae which were examined and segregated reproduced psedo- genetically under similar conditions, about 2 weeks after birth. This would allow for four laboratory paedogenetic generations before the appearance of the male pupae.



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Psyche
Table 1.
Sex of Imagines and Pupae produced by Paedogenetic Paedogenetic Origin.
Culture Pupae No. of Q Q No. of cf c?
arose by
A.
Bi2, Cr2 crowding 10 18
M 79 crowding 1 1
MNO 340 crowding 1 1
B. Female-producing strain.
4XXF3 crowding 38 0
4XXF6 (M222) crowding 2 6 0
4XXF6 (M223) crowding 2 3 0
4XXFo (M224) crowding 5 9 0
X8F2 crowding 1 0
C. Male-producing strains.
MN320 crowding 0 5
C02 3 C02 0 5
Larvae of Known
Total Per Cent
ofcfc?
All cultures were maintained on the standard artificial culture medium, described earlier in this paper, under as nearly identical external conditions as possible, save culture COz 3. The mother of the five imagines which appeared in this culture was treated with carbon dixoide at birth, and for some time subsequently, after which she was transferred to the standard medium employed in these studies. In all cases cultures were maintained in closed boxes in the same incubator, thus being exposed to similar conditions in respect to temperature, humidity, and light, as well as food. Thus the conclusion seems warranted that the observed sex-ratios are the expression of an internal mechanism, which, in the present instance in all probability, has not been greatly affected by external conditions (save possibly in the case of the strain produced by the psedogenetic mother larva which was treated with carbon dioxide.) Sufficient data are not yet at hand to warrant a statement concerning whether or not the carbon dioxide treatment changes the sex- ratio as in Cladocera (Banta 1923).
Summary.
Males as well as females arise from mass cultures of larvae that have been produced by psedogenesis in Oligarces sp. But males and females are not produced by the same in- dividual, under normal conditions.




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19241 Sex of Adult Cecidomyid (Oligarces sp.) 153 In the descendants of members of a colony taken from nature there were found to be two types of psedogenetic larvae in respect to the sex of pupae and aduk which they produced, (1) male-producing, and (2) female-producing. These two types of psedogenetic larva are not morpholo- gically distinguishable.
The evidence indicates that the distinction is genetic, since it holds not only in the case of a given individual, but also, without observed exception, in its offspring through five genera- tions of paedogenetic reproduction in two of which certain numbers of adult forms were produced.
Thus the potentiality for producing only males or only females seems to be inherited; there existing in t.he colony male-producing and female-producing strains. Banta, A. M. and Brown L. A., 1923. Further control of sex in a species of Cladocera. Anat. Rec. Vol. 24, Abs. 144 p. 420. Edwards, F. W. 1919. Some Parthenogenetic Chironomidse. Ann. Mag. Nat. Hist. (9) 3; 222-228.
Felt, E. P. 1911. Miastor americana. An account of pedo- genesis. New York State Mus. Bull. 147; 82-104. Goetghebuer, M. 1913. Un cas de parth&ogen&se observe chez un Diptere Tendipedide (Corynoneura celeripes). Bull. Acad. Roy. Belgique. 1913, 231-233. Grimm, 0. 1870. Die ungeschlechtliche Fortpflanzung einer Chironomus-Art und deren Entwicklung aus dem unbe- fruchteten Ei. Mem. Acad. Imp. Sci. St. Pktersbourg s6r. 7, tome 15.
Harris, R. G.
1923, 1. Sur la culture des larves de Cecidomyides psedogenktiques (Miastor) en milieu artificiel. Comptes Rendus Soc. de Biol. Paris, Tome 88 p. 255-7. Harris, R. G. 1923, 2. Occurence, Life-cycle, and Maintenance under Artificial Conditions of Miastor. Psyche Vol XXX. p. 95-101.




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154 Psyche [June-August
Harris, R. G. 1923, 3.
Control of the Appearance of Pupa-
larvae in Psedogenetie Diptera. Proc. Nat. Acad. Sci. Washington, Vol. 9-407-413.
Harris, R. G.
1924, 1. Further Data on the Control of the Appearance of Pupa-larvae in Peedogenetic Cecidomyidse. (Oligarces sp.) in press.
Harris, R. G. 1924, 2. Reversal of Function in a Species of Oligarces (in press).
Johannsen, 0. A. 1912. Parthenogenesis and Psedogenesis in Tanytarsus. Maine Agr. Exp. Sta. Bull. 187; 3-4. Kahle, W. 1908. Die Padogenesis der Cecidomyiden. Zoolo- gica. Bd. 21. Heft. 55. 80 pp., 6 plates. Meinert, F. 1864. Weitere Erlauteru~gen uber die von Prof. Nic. Wagner beschriebene Insectenlarven, welche sich durch Pprossenbildung vermehrt. Zeits. wiss. Zool. 14; 394-399.
Sturtevant, A. H. 1923. The Probable Occurence of Par- thenogenesis in Ochthiphila polstigmata. (Diptera). Psyche vol. XXX 22-27.
Wagner, N. 1863. Beitrag zur Lehre von der Fortpflanzung der Insecten-larven. Zeits. wiss. Zool. 13. 513-527. Wagner, N. 1865. Ueber die viviparen Gallmucke~larven. Zeits. wiss. Zool. 15, 106-107.
Acknowledgement is made to Dr. C. B. Davenport for facilities offered in connection with this work at the Department of Genet-ics of the Carnegie Institution of Washington at Cold
Spring Harbor.




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