Aug. a$, 1923 
Twinning and Monembryony in Platygaster hiemalis 349 
Platygaster hiemalis exhibits both types of development, it furnishes a 
clue to the origin of polyembryony in insects. 
(11) It is believed that the monembryonic development of some of 
the eggs, and the fact that some of the eggs of a group are inseminated 
while others of the same group are not, will account for the origin of 
mixed broods of the parasites, and the occurrence of single individuals of 
a sex different from that of the others of the brood. 
LITERATURE CITED 
(1) Hill, Charles C. 
1922. A PRELIMINARY ACCOUNT OF TWO SERPHOID (PROCTOTRYPOID) PARASITES 
OF THE HESSIAN fly. In Proc. Ent. Soc. Wash., v. 24, p. 109-117. 
(2) Leiby, R. W. 
1922. THE POLYEMBRYONIC DEVELOPMENT OF COPIDOSOMA GELECHIAE, WITH 
notes on its biology. In Jour. Morphology, v. 37, p. 195-285, pi. 
1-18. 
(3) Marchal, Paul. 
1904. recherches sur la biologie ET le d^velloppement des hymenop- 
t£res parasites, i. la polyembryonie sp£cifique ou germino- 
gonie. In Arch. Zool. Exp. et G6n., s£r. 4, t. 2, p. 257-335. 
(4) — 
1906. RECHERCHES SUR LA BIOLOGIE ET LE D^VELOPPEMENT DES HYM^NOP- 
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G6n., s6r. 4, t. 4, p. 485-640, pi. 17-24. 
(5) Patterson, J. T. 
1917. STUDIES ON THE BIOLOGY OF PARACOPIDOSOMOPSIS. III. MATURATION 
AND fertilization. In Biol. Bul., v. 33, p. 57-66, 2 pi. 
( 6 ) - 
1919. polyembryony and sex. In Jour. Heredity, v. 10, p. 344-352, 2 fig. 
(7) — 
1921. sex ratios in platygaster. In Amer. Nat., v. 55, p. 180-183. 
1921. the development of paracopidosomopsis. In Jour. Morphology, V. 
36, p. 1-69, pi. I—12. 
(9) Silvestri, Filippo. 
1906. CONTRIBUZIONI ALLA CONOSCENZA BIOLOGICA DEGLI IMENOTTERI PARAS- 
SITI. I. BIOLOGIA DEL LITOMASTIX TRUNCATELLUS (DALM.). In Alin. 
R. Scuola Sup. Agr. Portici, v. 6, 51 p., 5 pi. 
(10) — 
1914. PRIME FASI DI SVILUPPO DEL COPIDOSOMA BUYSSONI (MAYR). IMENOT- 
tero calcidide. In Anat. Anzeiger, Bd. 47, p. 45-46, 30 fig. 
1916. SULLA MATURAZIONE DELL’OVO, FECONDAZIONE E FORMAZIONE DEL 
TROPHAMNIOS NEL PLATYGASTER DRYOMYIAE SILV. (iMENOTTERO 
proctotrupide). In Atti R. Accad. Lincei, Rend. Cl. Sci. Fis., 
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