216 



with honey and water being inserted, and the tubes are then sent out 

 for colonisation. Material for colonisation of A. bifasciatus is obtained 

 from collections made in the field of gipsy moth eggs which are heavily 

 parasitised. Similar trays are used to those described above, the eggs 

 being covered with several layers of mosquito netting ; as the non- 

 parasitised eggs hatch, the larvae crawl up through the netting and 

 into the glass tubes, and are then destroyed by immersion in kerosene. 

 When hatching is complete, the eggs are passed from the trays over a 

 gravity chute and at a certain point the egg-shells and dead eggs are 

 drawTi off by suction, while the heavier parasitised eggs pass into a 

 tube at the base of the machine. These are measured off into cubic 

 centimetres, each of which will consist, on an average, of 1,000 eggs, 

 and are kept in a cool place until colonisation begins. 



S. kuvanae is liberated in the autumn, in colonies of about 3,500. 

 In the case of heavy infestation, the colonies are placed all along the 

 roads in a town, 200 to 300 feet from the roadside and about 2 miles 

 apart. The insects are then shaken out of the tube, the position of 

 the colony being marked on a neighbouring tree and noted on a map. 



A. bifasciatus is liberated during the spring as a larva within the host 

 egg, and as the rate of dispersion is much slower than in the case of 

 *S. kuvanae, the colonies are placed every quarter of a mile along the 

 infested roads, about 100 feet from the roadside. Each colony is 

 placed in a small tin can with three exit-holes in the side, which is 

 nailed to a tree and its position noted. 



In order to determine the measure of success of each colonisation, 

 collections of 100 gipsy moth egg-clusters are made from the neigh- 

 bourhood of several colonies. These are examined in the laboratory 

 and a record taken of the number of parasites that issue. For the 

 purpose of measuring the dispersion and increase of >S. kuvanae, four 

 lines are taken to the cardinal points of the compass, using the site of a 

 colony as the centre ; collections of egg-clusters are made at the centre 

 and at all points every 220 yards along these lines. For A. bifasciatus, 

 eight lines are selected and collections made from the centre at 

 every 100 feet for the first 200 yards and then every 100 yards. 

 These lines are carried to the limit of the colony, which in some cases 

 is nearly 2 miles. The collected eggs are sifted at the laboratory and 

 the amount of parasitism determined. In the winter, when the larvae 

 of A. bifasciatus are counted, they can be plainly seen in the gipsy moth 

 eggs ; while the numbers of S. kuvanae are estimated from the eggs 

 that show exit holes of the parasite. A plan is given showing the 

 method of measuring the percentage of parasitism by means of lines 

 crossed by concentric circles in the manner described. 



McCoLLOCH (J. W.). A Method for the Study of Underground Insects. 

 — Jl. Econ. Entom., Concord, N.H., x, no. 1, February 1917, 

 pp. 183-187, 1 fig. 



The construction of an underground cave placed eight feet below 

 the ground level, with the roof two feet below the surface, has proved 

 a very successful method for studying insects which injure roots and 

 seeds, such as white grubs [Lachnosterna], wireworms, etc. A list is 

 given of 17 species which were successfully carried through the winter 

 in this way. 



