390 JOURNAL OF ECONOinC EIf«PiMPBPWr fToF. 2 



about eight feet above the floor and the outer one about eleven feet, 

 giving a one-half pitch. The outer roof is of the heaviest sail cloth, 

 while the inner is of twelve ounce canvas. This arrangement 

 prevents any leaking through the outer roof, on account of the strong 

 pitch, and cuts out the heat of the sun, by the air current between 

 the two. The lower roof also protects the upper from the strain of 

 the wind coming through the screen sides. At the outer gable end 

 the gable is covered by canvas down to the screens. Each roof is 

 really a fly, with a broad seam on each side through which a strip is 

 run and is then screwed to the sides, thus affording a means of tight- 

 ening the roof should it stretch. After four months, with many 

 heavy winds, the roof shows no signs of wear. The spaces between 

 the upright supports for the roof are filled in between the roofs so 

 that the rearing room is absolutely tight for all ordinary insects too 

 large to pass through an 18-mesh screen. 



It is believed that this house affords as nearly natural conditions 

 as possible consistent with an enclosure. Insects which pass the 

 winter in the soil may be reared in cages placed on the pits or in cages 

 on the soil side of the floor, and left there throughout the winter 

 under normal conditions and cages then placed over them when the 

 house is erected in the spring. Many of the details of construction, 

 and indeed the whole house, must be regarded as an experiment, but 

 from the experience of the Bureau of Entomology with more tempo- 

 rary structures in their work at the Gypsy Moth Laboratory at Melrose 

 Highlands, Mass., it is believed that the general principles upon 

 which the house is based are worthy of such a trial as they will now 

 have. 



The whole structure cost approximately $400. Of this nearly one- 

 third was for the grading and cement work. About one half of the 

 total cost was for labor and one half for materials. The double roof 

 cost $47. The screens, including two doors and two window screens 

 for the workroom, with the sixteen around the rearing room cost $70. 

 Lumber cost about $50. Where no gradings were necessary and 

 where a house could be built from plans previously developed, ours 

 developed as we progressed, such a house could probably be built for 

 $300. "We shall be glad to furnish any further details of structure 

 to any who may be interested. 



