10 Bulletin American Museum of Natural History. [Vol. XXIII, 



insect hatches. The changes from the stage represented in Fig. 21 to that 

 of Fig. 23 can hardly require more than three or four days. If this and my 

 estimate concerning the rate of development in the earlier stages is correct, 

 we must suppose that 0. viridis completes its entire life-cycle, from the egg 

 to the imago, in less than a week or ten days. Similarly rapid developments 

 are known to occur in other Chalcidids, as I infer from the following 

 statements in an interesting paper published some years ago by Howard ^ : 

 ^'Ratzeburg has shown that in Europe Pteromalus puparum occupied on one 

 occasion from June 11 to July 14 to undergo its entire transformation from 

 egg to adult — • thirty-seven days ; but in this country Webster has recorded 

 an instance (Insect Life, I, 225) in which the eggs of the same parasite were 

 laid August 9, the adult insect developing August 27 — seventeen days later. 

 Hubbard has noted (Fourth Report U. S. Ent. Com., p. 103) that the egg 

 of Aletia xylina gives forth the adults of Trichogramma pretiosa on the 

 seventh day after it Avas stung by its parents. Euplectrus comstockii has 

 been shown by Schwarz to develop from egg to adult in Alabama in mid- 

 summer in seven days." 



There can be little doubt that in a state of nature the male and female 

 Orasemce leave the nest very soon after hatching and mate in the open fields. 

 This is indicated by their strong positive phototropism. The fertilized 

 females then seek out fresh Pheidole nests in which to lay their eggs. In 

 one of my artificial nests, however, which was kept from June 19 to Septem- 

 ber 20, three successive broods of Orasema were noted, the last disappearing 

 about a week before the latter date. In this case, unless the offspring arose 

 from parthenogenetic eggs, the males and females must have mated in the 

 nest. Both in this and other cases it was found that the adult Orasemce, 

 after they had remained in the nest for several days, were killed and dis- 

 membered by the workers, as though the parasites had at last been recog- 

 nized as predatory aliens. This slaughter, however, may have been due 

 to other causes, since the workers also killed and dismembered their own 

 females and ultimately reared only workers and intermediates, probably 

 because these required less nourishment. Such conditions point to a 

 deterioration of the colony and are frequently observed in artificial nests 

 inadequately furnished with food. Similar behavior on the part of workers 

 may be seen in other species of ants when the food supply becomes insuffi- 

 cient or is no longer palatable. Under these circumstances I have seen 

 Camponotus ferrugineus workers kill and dismember their soldiers and 

 Myrmica hrevinodis workers do away with their males. 



Before concluding this account of the relations of 0. viridis to Ph. 



'The Biology of the Hymenopteroiis Insects of the P'aniilv Clialcididfe. Proceed. U. S. 

 Nat. Mus., XIV, 1892, pp. 567-588. 



