66 



THE GRAPE EOOT-WORM. 



During the summer of 1909 parasitized eggs were in evidence in 

 the field from July 20 to August 30, and were found locally quite 

 abundant, though less so than Fidiohia jlavipes. Professor Yv^ebster 

 informed the junior writer that he had found a similar parasite in 

 Ohio in 1896. Table XXIII shows the relative occurrence of para- 



PlG. 



-Larva of an undetermined insect parasite of the eggs of the grape root-worm. (Original.) 



sitized eggs as observed at various stages in different localities during 

 1909 at North East, Pa. 



Table XXIII. — Percentage of eggs of the grape root-worm parasitized hy a dipterous 

 insect, as observed in vineyards in the vicinity of North East, Pa., 1909. 



Date. 



Vineyard. 



Per cent. 



July 20 

 July 22 

 July 24 

 Aug. 4 

 Aug. 12 

 Aug. 19 

 Aug. 2G 



Davidson 



Porter 



Mosher 



Algren 



do 



do 



do 



1 



1 



3 



7 



22 



12 



14 



It will be noted that there is an increase in the occurrence of the 

 parasite toward the end of the season, as was observed with Fidiobia. 



Root-worm eggs parasitized by this insect are in their early stages 

 opaque-white in color. Later the eggshell becomes semitransparent 

 and iridescent. The larva of the parasite when full-grown is almost 

 twice the length of the host and lies folded within the o^gg. The 

 whitish larvae are very active on emerging from the hosts. They 

 were found to penetrate several inches in the soil in glass jars. Though 

 the larva is quite common, all attempts to rear the insect to obtain 

 the adult or fly have so far proved fruitless. 



DOUBLE PARASITISM. 



August 30, 1909, a cluster of 115 root-worm eggs was collected, 

 which were infested by the dipterous parasite. The egg along the 

 border of the cluster, unlike the rest, a few days later assumed a pink 

 color, but at the same time showed the iridescence characteristic of 

 this parasite. Dipterous larvae emerged September 3 from the eggs 

 of the central portion of the cluster. From the eggs along the border 

 of the cluster a hymenopterous fly {Lathromeris fidise Ashm.) (fig. 27) 



