AXD OTIIKR INJl'RIOUS INSRCTS OF I907 AND KjOcS. 



131 



cabbage. Out of the 50 plants of this variety nearly all produced solid 

 heads. Forty sound heads were counted August 27th. 



Red Cabbage: Fifty Rock Red cabbage were planted May 17th between 

 rows of cauliflower. These plants were in soil badly infested with cabbage 

 maggot last year. The cauliflower was a complete failure, there being 

 only three heads out of the fifty plants when counted July 26th. On August 

 13th Mr. Ainslie found a large red cabbage which had been practically cut 

 off by maggots. Only 12 heads of the red cabbage (out of the 50 planted) 

 were found when counted August 27th, and none of these were large heads. 



EXPERIMENT NO. 20— PARASITICAL AND PREDACEOUS 



ENEMIES. 



Several hundred Pegomyia puparia were collected in the spring on the 

 ground which was planted in cauliflower and cabbage the preceding year. 

 This was for the purpose of rearing parasites on the imago. i\Ir. Webster 



reports on these as follows : 

 "Pseiidoeucoila gillettei (see Fig. 

 67) was tlie most common para- 

 site that emerged from the col- 

 lected puparia, but a number 

 of others were also reared." Spec- 

 imens of these other parasites 

 were sent to Dr. C. T. Brues, 

 Public Museum, Milwaukee, Wis., 

 and determinations were made by 

 him. 



Homotropus hicapillaris Walsh, 

 var. albopictus Davis. A single 

 specimen emerged June 6th. 

 There is a possibility that this 

 is not a bona fide parasite of 

 Pegomyia, since other members of 

 the genus are parasitic upon Syr- 

 phid larvae. Syrphid puparia 

 may accidently have been collect-, 

 ed along with Pegomyia puparia. 

 Stiboscopus sp. (?) One male 

 specimen was reared June 2nd. This seems to be a primary parasite of Pegomya. 

 This is probably a new specie. Females are necessary for study to be positive. 

 Dacnusa, n. sp. One specimen emerged June 13th. Other members of 

 this genus are parasitic upon Agromyza and Phytomyza, and also accord- 

 ing to Retzeberg, upon Saperda. This is evidently a primary parasite of 

 Pegomya. 



Aphacrcta pegomyiae Brues. Thirteen specimens emerged in one cage 

 on June 2nd {A. dimidiata Ashm. has also been reared from Pegomya brassicae) . 

 Megaspilus striatipes Ashm. One specimen emerged June 10th. M. syr- 

 phi has been reared from Syrphus rihis and from S. balteatus according to 

 Bouche, and there is a possibility that our species may also have been para- 

 sitic upon some Syrphid puparia collected with those of the cabbage maggot. 



Fig. 67. P. niUeUei. en\a.rse(\. Original. 



