180 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



yards along these lines. These collections are brought to the labora- 

 tory where the hair is removed from the clusters by rubbing them over 

 a piece of cheesecloth drawn taut over a small tray. The eggs are 

 examined with a binocular microscope and the percentage of parasitism 

 determined. It is quite easy to observe the Anastatus maggot within 

 the gipsy moth egg and, with a little practice, this work can be done 

 quite rapidly. It has been found that one cubic centimeter contains 

 on an average 1,000 eggs, so that the eggs are measured, the parasi- 

 tized ones counted, and the percentage of parasitism is thus determined. 

 The collections are continued along the lines until the parasitism drops 

 below 10 per cent. From the territory inside the 10 per cent limit on 

 all the lines, egg clusters are collected during the winter to obtain 

 material for further colonization. Last year five bushels of egg clus- 

 ters were collected from this colony and were sifted by means of a 

 special machine which was devised by Mr. C. W. Stockwell of the 

 laboratory force. This sifter not only saves a great amount of labor, 

 but eliminates, to a great extent, the irritation in the nose and throat 

 caused by the dust and hairs which always results when this work is 

 done by hand. This machine is made on the principle of the old- 

 fashioned grist-mill, but is so adjusted that the eggs are not injured. 

 It consists of two horizontal disks three feet in diameter, which are 

 padded on the inner surfaces. The eggs are fed to the machine auto- 

 matically from a box which rests on the top. The upper disk revolves 

 slowly, removing the hairs from the eggs as thej^ are worked toward the 

 circumference where they fall on to a chute and assemble in a trough. 

 The power is furnished by a small electric motor. The hair and dust 

 are removed through a suction pipe by means of a small electric blower. 

 After the eggs are sifted they are spread evenly over the bottom of 

 the trays. Several layers of cloth mosquito netting are placed over 

 them and the trays are made dark and tight by covering with black 

 paper. Holes are made in the side, into which glass tubes are fitted. 

 As the non-parasitized gipsy moth eggs hatch, the larvae crawl up 

 through the netting and into the glass tubes from which they are de- 

 stroyed by being placed in a jar of kerosene oil. Much of the silk spun 

 by the caterpillars becomes entangled in the netting, so that the parasi- 

 tized eggs are quite free from it. After hatching is completed, the 

 parasitized eggs, dead eggs, and egg shells are taken from the trays 

 and separated by means of another machine devised by Mr. Stockwell. 

 The eggs run by gravity over a chute, and at a certain point, the egg 

 shells and dead eggs, which are lighter than the parasitized ones, are 

 drawn off by suction, while the heavier parasitized eggs continue on 

 into a tube at the base of the machine. As one cubic centimeter con- 

 tains on an average 1,000 eggs, these are measured and placed in 



