58 RESULTS FROM GIPSY MOTH PARASITE LABORATORY. 



semipupa, but occasionally it is placed on the back of the neck between the head and 

 the i)rothoracic segment or on the right or left side of the neck beneath the correspond- 

 ing protlioracic leg. These regions would seem to be singularly a})propriate, both 

 because the cuticle is extremely thin and readily punctured by the parasitic larva at 

 these points, and also because the egg or resulting larva, especially when it is covered 

 with the overlapping appendages of the semipujia, is not so readily brushed or licked 

 off by the instabiUs workers. 



If we may judge from the habits of Perilampus, the explanation of 

 Dr. Wlieeler's failure to find the eggs of Orasema in the ant nest is 

 possibly that they are not deposited there. It is possible that ovipo- 

 sition might take place outside the nest, perhaps upon flowers or other 

 vegetation visited by both the Orasema adults and the worker ants; 

 and that from the eggs deposited upon these plants the planidia 

 hatch, in some manner attach themselves to the worker ants, and are 

 in that way conveyed to the nest, where they leave their carrier and 

 attack the larvae. Several points in the economy of Orasema as 

 noted by Dr. Wheeler tend to substantiate the belief that oviposition 

 takes place outside the nest. In the first })lace the large number of 

 eggs deposited by Orasema (Dr. Wheeler found by dissection of the 

 adults that they were very numerous and minute) indicates that some- 

 where in its early life cycle there is prevalent a very great mortality. 

 That this mortality actually takes place was observed by Dr. Wlieeler, 

 and he thought that it might be explained in the following manner: 



I believe that the danger of detaching the egg is very great, and this, together with 

 the other special requirements enumerated above, may account for the fact that com- 

 paratively very few of the great number of Orasema eggs ever complete their develop- 

 ment. 



The number of eggs deposited by a single female Orasema, should 

 they all become effective, would probably be sufficient to annihilate 

 a whole colony of the Pheidole, and not one but many female Orasema 

 are usually found in the infested nests. It would seem, therefore, 

 that there would be little likelihood that such great mortality would 

 occur if only the causes enumerated by Dr. Wheeler were operative. 

 It is possible that the Orasema planidia attack the larvae of Pheidole, 

 not the pupge, and that the seemingly sudden appearance of the 

 young Orasema larvae upon the pupae of Pheidole immediately after the 

 last larval ecdysis is similar to that which has been noted on a preced- 

 ing page as occurring in Perilampus. In other words, the Orasema 

 })lanidiuni may be endoparasitic within the Pheidole larvae, making 

 its exit to the exterior at the time of histolysis and feeding ectopara- 

 sitically thereafter. Dr. Wheeler's observation of the fact that the 

 Orasema planidia appear upon the pupae only at this critical time 

 would tend to substantiate this theory. 



It seems imj^robable that insects as highly jwsitively phototropic 

 as Dr. Wheeler has observed Orasema to be slioidd return to the 

 interior of an ant's nest to oviposit after having escaped and lived in 

 the sunlight for a considerable time. 



