Dec, '12] RUSSELL AND JOHNSTON: BIOLOGY OF TETRASTICHUS 433 



as they had emerged from the pupae began oviposition in the host eggs 

 and the adults were reared in these experiments. 



In confinement this insect has continued oviposition from 1 to 17 

 days and lived from 5 to 21 1-2 days and during that time oviposited 

 in from 1 to 41 eggs of the host besides destroying from 1 to 61 by 

 feeding. In the few eggs of the host that have been dissected from 1 

 to 5 eggs of the parasite were found. 



The egg of the parasite is reniform with one end more slender than the 

 other, about 0.24 mm. long and 0.0825 mm. wide, and is of semi- 

 transparent milky color with a granular appearance within. While 

 the eggs may be laid singh', in a number of cases they were found in 

 pairs side by side. 



In rearing this parasite from 1 to 9 adults have emerged from a single 

 host larva, so tnat apparently for every egg of the parasite one adult 

 results. Polyembryony, therefore, as in Encyrtus, Litomastix, and 

 Copidosoma, so fully studied by Dr. Paul ]\Iarchal^ and others and 

 reviewed by Dr. L. O. Howard,'' appear not to occur in Tetrastichus 

 asparagi. 



Apparently this insect has three generations a year in Long Island, 

 for it was very abundant early in June at the time the first generation 

 of the host was appearing, after which it disappeared, only to be found 

 again in July with the second generation of the host. Since that time 

 two generations have been reared under nearly normal conditions. 



Undoubtedl}^ this is a parasite of much promise, for not only does 

 it check the asparagus beetle by its parasitic development, but it seems 

 to do even more good from its habit of feeding so energetically on the 

 eggs of this insect. The field where these observations were made has 

 until this year always been sprayed to prevent serious injury by the 

 asparagus beetle, but this year, although it received no treatment 

 whatever, the asparagus beetles Avere so scarce that no damage resulted. 



5 Recherches sur la Biologic et le Developpement des Hymenopteres Parasites — 

 La Polyembryonie Specifique on Geiminogonie. Arch. Zool. Exp. (4), vol. 11, pp. 

 257-335, pis. IX-XIII (1904). 



« Polyembryony and the Fixing of Sex. Science n.s., vol. 24, pp. 810-818 (1906). 



