36 RESULTS FROM GIPSY MOTH PARASITE LABORATORY. 



A comparison of the peculiar first-stage Perilampus larva with the 

 Orasema material in Dr. Wheeler's possession indicated that wliile the 

 two were veiy different in anatomical detail, they were of the same 

 general character and constitute a type which, Dr. Wheeler has sug- 

 gested, may be designated by the term ''planidium." ^ 



The establishment of the identity of the planidium did not assist 

 materially in clearing up the mysterious circumstance attending the 

 rearing of the Perilampus from the Limnerium, VaricJiseta, and 

 Apanteles parasitic on the fall webworm, and with the end in view 

 of determining if possible the manner in wliich Perilampus gained 

 access to its host, several thousand young caterpillars of HypTiantria 

 were collected during the following fall, placed in rearing trays, and 

 reared to maturity. At frequent intervals a large series of these 

 caterpillars was killed and preserved in order that abundant mate- 

 rial might be had for study during the winter. 



Apanteles hyphantrise Riley was found to be a fairly common 

 parasite of the younger caterpillars, and VaricJiseta aldricJii and 

 Limnerium validum of the older ones, as during tlie preceding 

 summer. Examination of the puparia and cocoons of the parasites 

 disclosed the fact that the planidia of Perilampus were even more 

 common than they were during the preceding year, and as large 

 quantities of material in all stages had been preserved an excellent 

 opportunity was afforded for working out the hfe liistory of this 

 remarkable parasite. 



As has been mentioned on a preceding page, Perilampus was 

 frequently reared from puparia and cocoons formed in tight rooms 

 or breeding cages into which it was thought impossible for an adult 

 parasite to gain entrance. Consequently in seeking an explanation 

 of the presence of the planidia of Perilampus in the puparia and 

 cocoons of these primary parasites of HypTiantria, it seemed most 

 plausible that the female oviposited in or on the caterpillar con- 

 taining the parasite wliich was later to become the host of the young 

 Perilampus. Acting upon this hypothesis, maggots of the tacliinid 

 which had emerged from the caterpillar were examined and found 

 to contain the planidia internally. The planidium, by reason of its 

 dark color, was easily visible through the semitransparent integu- 

 ment of the maggot, and even after the latter had ceased activity 

 and had formed its puparium the Perilampus larva could be seen 

 through tlie shell until it had changed color and had become quite 

 opaque. Dissection of the fully developed caterpillars revealed the 

 fact that the tachinid maggots while still within the caterpillar con- 

 tained these planidia, and going back still further, to the younger 

 caterpillars, the planidia were found to be present here irrespective 

 of whether the caterpillar was infested by a primary parasite or not. 



I i'roiu the Greek 7zka>j)xi)c, a wanderer, and idim, diminutive. 



