THE CHALCIDOID GENUS PEEILAMPUS. 57 



dead when found upon the Limnerium larvae in the fall. Out of 11 

 specimens found during an examination of some 55 cocoons, 10 were 

 dead and shrunken. These cocoons had been kept under perfectly 

 natural conditions out of doors, so that it is obvious that there was 

 something radically wrong between parasite and host. The fact that 

 it has never been found upon VaricJiseta suggests the possibility of its 

 being of ectoparasitic habits entirely, and that it attaches itself to 

 the Limnerium larva after the latter emerges from the caterpillar, but 

 prior to the spinning of its cocoon. This would of course preclude its 

 being a parasite of a tachinid, as the formation of the puparium would 

 naturally leave it outside of- the hardened shell and death would inevi- 

 tably result. The data on hand concerning this species, however, are 

 too limited to warrant an attempt to draw any conclusions, and with 

 the recording of the above facts we leave it until further investiga- 

 tions have thrown more light upon its habits. 



DEVELOPMENT OF ORASEMA. 



Dr. William Morton Wheeler, in the article referred to on page 35, 

 gives an exceedingly interesting account of the life history and 

 economy of the chalcidoid genus Orasema, of the family Eucharidse. 

 A comparison of the habits of representatives of the so-called fami- 

 lies Eucharidse and PerilampidiB is of unusual interest at this time 

 and may assist in clearing up certain doubtful points in the economy 

 of the former. Orasema is parasitic principally upon the harvestmg 

 ant Pheidole instabilis Emery, but also occurs not uncommonly upon 

 representatives of other ant genera in the southwestern United States 

 and Mexico. In view of the close relationship existing between the 

 two genera and the general similarity of development so far as is 

 known in the two forms, it would seem permissible at this time to 

 draw certain conclusions in regard to Orasema which have been sug- 

 gested by the investigations upon Perilanipus. In regard to the ovi- 

 position of Orasema Dr. Wheeler has the following to say: 



I have not seen the eggs of 0. viridis after oviposition, but only the very young 

 larvae. Dissection of the female shows that, as we should expect in a parasite, the 

 eggs are extremely numerous and minute. The mother insect, when she comes to 

 oviposit, exercises a very careful selection among the ant brood. In the first place 

 she has nothing to do with the instabilis larvae, but directs her attention to the pupae. 

 In the second place she selects, as a rule, only the pupae of the soldiers, males and 

 females. The small worker pupae would not furnish sufficient food for her larvae. In 

 the third jilace she selects only pupa? at the very critical moment when they have 

 been stripped of their larval skin by the workers and are, therefore, little more than 

 semipupae, for obviously at this moment the cuticle is thinner and will be more easily 

 pierced by the young Orasema larvae than during the preceding or succeeding stages; 

 and in the fourth place she does not lay her eggs at random anywhere on the body of 

 the semipupae, but carefully selects one of four regions near the head. Usually she 

 places the egg on the sternal surface just beneath the very short, incurving legs of the 



