138 PROC. ENT. SOC. WASH., VOL. 23, NO. 6, JUNE, 1921 



was unfortunately broken in collection and the parasites could 

 not be reared; no other hyperparasites have since been discov- 

 ered. 



GEOGRAPHICAL DISTRIBUTION. 



Zenillia roseanae has been found in Pyrausta larvae in several 

 of the departments of southwestern France (Gers, Hautes Py- 

 renees, Landes), and in the Mediterranean region at Hyeres 

 (Var) and Men ton (Alpes Maritimes). In material from 

 southern Germany (southern Wurtemberg) and Belgium, it 

 has not been discovered. It would thus appear to be a southern 

 species; but so far it has not been found in material from Naples 

 and it seems to be rarer along the Mediterranean littoral than 

 in the region north of the Pyrenees. 



IMPORTANCE AS A CONTROLLING FACTOR OF THE CORN BORER. 



In order to determine accurately the status of this species as 

 a controlling factor of the corn borer in Europe it will be neces- 

 sary to carry on an investigation continuing over a considerable 

 period. However from the data now available it would appear 

 that Zenillia roseanae is a very important parasite of Pyrausta 

 nubilalis. As it has two annual generations, both passed on the 

 borer, its introduction into the United States offers much less 

 difficulty than that of species with several generations which 

 develop in different hosts. Having two broods a year it should 

 be able to overtake and check the invasion of the host with com- 

 parative rapidity; and finally, the method of hibernation of the 

 species, in the hibernating caterpillars of Pyrausta, enables the 

 parasite to pass through one of the most difficult periods in its 

 seasonal history with a much lower mortality than is caused by 

 extreme unfavorable meteorological conditions and hyperpara- 

 sitism in the case of species which pass the winter in the pupal 

 or adult stages. 



LIST OF ILLUSTRATIONS. 



Fig. 1. Zenillia roseanae. First stage larva. 



Fig. 2. First stage larva; posterior extremity, seen from dorsal side; f". "felt- 

 chamber" of posterior stigmata; s. o. clavate sensory organ; s. s. 

 stigmatic spines. 



Fig. 3. Mouth-hook or bucco-pharyngeal apparatus of newly hatched, first stage 

 larva, b. r. basal region; d. w. dorsal wing of basal plate; i. r. 

 intermediate region; 1. p. lateral plates; in. t. median tooth; s. s. d. 

 sclerite of.the salivary duct; v. w. ventral wing of the basal plate. 



Fig. 4. Mouth hook or bucco-pharyngeal apparatus of larva at the end of the 

 first stage. 



