December, '09] JOURNAL OP ECONOMIC entomology 457 



believed to be an instance of this sort, and so far as known the former 

 is always the victim in such a conflict. The same is true of 

 Spilocryptus, undoubtedy a primary parasite and to be considered 

 as such. In several instances in which it was found in the same 

 cocoon as Ophion, it destroyed the larva, feeding upon it as an ex- 

 ternal parasite, exactly as it would have done upon the caterpillar had 

 it remained alive. In one instance the cocoons were found massed 

 within that of the Ophion, but usually the Ophion cocoon was incom- 

 plete or entirely lacking. In one instance no less than 10 healthy 

 larvce reached maturity; usually they were less, and sometimes only 

 a few, or none at all completed their development. The most interest- 

 ing examples were found in old cocoons, from which all the living 

 parasites had escaped. 



The outcome of double parasitism by Spilocryptus and Theronia 

 depends upon which is the first in the field. It is very probable but 

 unproven that the young, internal feeding Theronia is destroyed by 

 the external feeding Spilocryptus through deprivation of its food 

 supply. In one very extraordinary instance the Theronia reached 

 full development as an internal, and the other as an external parasite, 

 a state of affairs never before met with. In another, in which the 

 Spilocryptus was obviously the first to attack, a dead Theronia was 

 found in one of the several cocoons of the other. 



A study of the host remains in cocoons which had been attacked by 

 any of the parasites would probably result in the discovery- of evi- 

 dences of attack by other species which had been destroyed in such 

 an early stage in their development as to leave no conspicuous re- 

 mains. Spilocryptus. for example, is undoubtedly the victor in some 

 instances in which it conflicts with the Tachinid parasites. In others 

 it is likely to die as a result of the premature death of the host. 

 Ophion invariably kills its host before pupation, and the Tachinids 

 frequently, though not always afterward. There is a possibility, since 

 it is the first to mature, that occasionally it triumphs over them, but 

 this is not always the case. In two most remarkable instances, it was, 

 as usual, the victim. 



In each of these the Ophion cocoon, normal in appearance and 

 texture, w^as found in its usual situation within cocoon of cecropia, 

 and the walls of both were pierced by the characteristic exit hole of 

 the Tachinid maggots. The Ophion cocoon was empty, except for the 

 skin of the larva, and in spite of the almost conclusive evidence that 

 Tachinid maggots had somehow gained entrance and destroyed the 

 occupant, the circumstances were so remarkable, and altogether out 



