PKOCEEBINGS OF TUE THIRD ENTOMOLOGICAL MEETING HVi 



The first year's work showed that the breeding cages used were un- 

 suitable for the purpose. At that time the only cages available were 

 of the usual cubical shape with glass and wire gauze sides and a large 

 door at one side. Their principal defects were the rapid desiccation 

 produced in the log and the difficulty of preventing the escape of minute 

 insects when manipulating the emerged material through the large side- 

 doors. 



Special patterns of cages were therefore devised for this purpose. 

 Plate 139 shows various types of cages tested before satisfactory 

 results were obtained. The cages in the two upper rows are of deodar 

 wood with a square of wire gauze let into the roof and a hinged door 

 forming one side. The cages in the fourth and fifth rows are of loon wood 

 with a square of wire gauze in the roof, a sliding door at one end, and a 

 small hinged door in front. The cages in the bottom row are similar in 

 principle but of different design and dimensions to accommodate logs of 

 different sizes. In all these types the capture of the emerged insects is 

 effected by attraction to light. At first large test-tubes and glass 

 bottomed boxes were used, but it was found that, although insects readily 

 entered these traps, they were also able to leave them and return to the 

 cage. Glass retort-shaped bulbs were therefore substituted for tubes 

 and have been used ever since with complete success. 



The wooden cages used, however, did not eliminate the difficulty 

 of desiccation resulting from the long periods (one to two years) for which 

 the logs must be kept. Even with logs 4 feet long and 3 or 4 feet girth 

 much more heartwood moisture was lost in the insectary than would be 

 lost by the tree lying in the shade of the forest and exposed to rainfall. 

 Waxing the ends reduced the loss, but insufficiently. The evaporation 

 of moisture also caused considerable warping and cracking of the wood 

 work of the cages (some of the cages in the photograph show this). 



We have therefore adopted galvanized iron cages as the standard 

 design. These are illustrated in the 3rd row of Plate 139 and on a larger 

 scale in Plate 140. The dimensions vary. Those shown are 18 X 12 X 12 

 inches but we also use larger sizes capable of holding fairly representative 

 sections of the tree trunk. The door frame is made of seasoned shisham 

 and all the contact joints of the door and the frame are lined with felt 

 or velvet. The neck of the attraction bulb is held in a velvet lined 

 cylinder in wooden blocks screwed on either side of the iron sheet forming 

 the door. These cages are quite satisfactory, as they allow the regulation 

 of the rate of evaporation by means of desiccators and humectators 

 to suit all classes of timber, and conditions of atmospheric humidity. 

 Some have recently been fitted with hygrometers. 



