February, '17] CROSSMAlS: COLONIZING PARASITES 179 



Material for colonizing Schedius is obtained by breeding at the 

 laboratory. The trays used for this work are 5 feet long, 2| feet wide, 

 and 3 inches deep. They are lined with black paper and covered with 

 white cotton cloth. Two holes twelve inches square are cut in the top, 

 each half way between the center and end of the tray, through which 

 the Schedius are fed. Sheets of glass are placed over each hole to pre- 

 vent the adults from escaping. During the middle of August, about 

 25,000 gipsy moth egg clusters are collected from any convenient local- 

 ity to be used in the breeding trays. These are then slightly broken 

 and spread evenly over the bottom of each tray. About the same time 

 a few hundred egg clusters are collected from some locality where 

 Schedius is present and placed in glass vials, 8 inches by 2 inches, which 

 are examined daily. Soon adult Schedius of the first fall brood issue 

 and are transferred from the vials to the breeding trays, where they 

 have an abundance of gipsy moth eggs for oviposition. In this manner 

 each breeding tray is stocked with from 3,000 to 5,000 Schedius. Strips 

 of banana peel sprinkled with sugar are placed in the trays for food for 

 the Schedius. It is quite important that the breeding trays be kept in 

 a warm room, else the parasites do not oviposit freely. The breeding 

 trays are started at intervals over a period of two to three weeks, so 

 that the parasites issue continuously from the eggs in the trays during 

 the colonizing period, which extends from the last of September to the 

 middle of November. In about twenty-five days a new generation of 

 Schedius will be found issuing from the eggs in the breeding trays. 

 Just previous to the issuing period, the trays are darkened by placing 

 black paper over the glass in the tops and a series of one-inch holes are 

 bored through the side, into which are inserted paper cones which hold 

 glass tubes. Electric lights are now placed in front of the tubes and 

 after a number of Schedius have entered a tube, it is replaced by an 

 empty one. An estimate is made of the number of Schedius in this 

 tube; then by gently tapping it, the Schedius drop into an eight-inch 

 mailing tube. About 1,600 parasites are placed in each mailing tube, 

 and honey and water smeared on a piece of paper is enclosed for food. 

 These parasites are now ready for colonization and the tubes are either 

 mailed to men in the field or taken by them for immediate liberation. 



Material for colonization of Anastatus is obtained from collections 

 made in the field. Large collections of gipsy moth egg clusters are 

 made from heavily infested territory, where the percentage of parasi- 

 tism is high. The following method is used : There is a strong colony 

 of Anastatus in a town not far from the Melrose Highlands laboratory. 

 The exact location where the colony was liberated is taken as the 

 center and lines are run in eight directions: N, NE, E, SE, etc. Ten 

 egg clusters are collected at the center and at points every hundred 



