132 THE APPLK LEAF HOI'PEK 



Isocyrtiis pegoiiiyiac Brues, J\ls. One specimen emerged May 30th. This 

 may possibly be a secondary parasite, with Pseudoeucoila as intermediate host. 



Loxotropa pegoiiiyiac Brnes, Ms. Several specimens emerged Jnne 20th. 

 Tliis is probably a primary pjirasite. 



Mcsocrina pegoiiiyiac Brues. See page 192 of this report for techni- 

 cal descriptions of the three new species which are probably pr-imary par- 

 asites. 



Tile predaceous insects preying upon Cabbage Maggots were well fig- 

 ured and listed in our report for 1906, namely, several ground beetles (Car- 

 abidae), and particuarly the red mite known as Troinhidiiim scahriim Say, 

 which sucks their eggs. We have also to add. based upon observations in 

 1908. the little rove beetle. Alcociiaro iiitida LeConte, Fig. 69. 



EXPERIMENT NO. 21— LENGTH OF LIFE OF 

 PSEUDOEUCOILA. 



Three Pseudouecoila were confined in a small vial April 30th. and lived 

 until May 10th without being disturbed. Two were dead on that date, and 

 the third apparently dying. From this it seems evident that Pseudoeucoila 

 can live at least nine or ten days, and probably much longer than that under 

 natural conditions. 



THE EMERGENCE OF THE CABBAGE MAGGOT FLY AND THAT 



OF ITS PRINCIPAL PARASITE (PSEUDOEUCOILA 



GILLETTEI ASHM.) COMPARED. 



We use the term "principal parasite" in connection with P. gillettci 

 becatise it appears to have been the one most abundantly reared in the in- 

 sectary. We personally found it in the burrows of cabbage maggots in the 

 field in 1906, and reared it from puparia. 



This parasite -is a small four-winged fly about one-tenth of an inch in 

 length, shiny black in color. The antennae are slightly longer than the 

 body, and the legs are brown. It belongs to the Cynipidae, a family of in- 

 sects, most of which form galls, but containing a few parasitic forms. 



The parasites spend the winter within the puparia of the cabbage mag- 

 gots, emerging from these in the spring a short time after the cabbage 

 flies appear. The first appearance of Pseudoeucoila in our cages was April 

 26th, when Webster found a single specimen which had emerged from a 

 Pegomya puparia collected March 26th. The material was kept in a warm 

 room at the insectary, which fact will account for the early date of emer- 

 gence. This lot of puparia was gathered among cabbage and cauliflower 

 stalks in a garden at St. Anthony Park. A total of 46 per cent of these pu- 

 paria were parasitized by Pseudoeucoila. Specimens of the parasite con- 

 tinued to appear in insectary cages through the entire season, three emerg- 

 ing the latter part of the summer from puparia gathered in the spring. It 

 has been observed before by Prof. SHngerland tliat a part of the puparia of 

 the first brood did not give forth flies until late in the season. This peculiar 

 retardation of development was also found to be true in the case of Pseudo- 

 eucoila gillettci. 



