ELISHA MITCHELL SCIENTIFIC SOCIETY. 29 



edge of the hole, a horizontal wall to which particles are ce- 

 mented and pressed in shape to make a flat, circular, lid to 

 the tube.* 



By a study of Plate IV we shall see some of the variations 

 from the normal type. Vig. i, a, represents one of the 

 spiders, natural size, />, section of a nest built after the nor- 

 mil type, door represented open, alsonitural size. All of 

 the other fig-ures, except 15 and 16, are mignified. In fig. 

 2, one side of tube, a, is extended above ground and carried 

 over the tube. The door, represented open, is hinged at /> ; 

 when closed it slopes downwards from the hinge attach- 

 ment, fig. 3. This was the work of No. 3. The arched wall 

 from fi, was pressed in shape in the same way that the trap 

 door is, so that when the spider began it at n, I thought it 

 had begun the trap door, and m ide this entr}^ in my notes: 

 "At 4.30 door begun ; two-thirds of the edge used for attach- 

 ment of the hinge, making an awkward door." When the 

 hinge was m:ide at A, it was easy to see the arching of the 

 wall was intentional. In fig. 10, the tube is curved above 

 ground in a similar way, but the hinge is at one of the slop- 

 ing sides, m iking a door that swings to the right and left in- 

 stead of up and down. This wms mideby No. 25. Fig- 

 ures 4, 5, 6 and 7 represent the work of No. 15. A trench 

 was dug, using the excavated eirth for a wall on each side ; 

 the walls were then united by an arch over the middle, one 

 end closed and a trap-door made at the other end. Fig. (S, 

 represents the nest of No. 22, built in the same way as that 

 of No. 15, except that at a, the hole was not entirely closed. 

 No. 13 built what is shown in fig. 9. A trench with a wall 

 each side was first built; in the middle of the trench was due 

 the tube and the door hinged at the base of one wall at *-/, 

 with the distal part of the door elevated at h. Fig. 11, 

 shows the work of No. 24; a trench was dug b\' the side of 

 the glass with a wall on one side at o ; on the other side 

 earth was carried upon the side of the glass and attached in 

 small lumps at A; f\ represents the nest, a small tower 

 against the glass. Fig. 12, was made by No. 26. This is 

 interesting as being the only one showing the concentric 

 " lines of growth" usually noticed in the doors of nests that 

 have been used for a year or so. No. 14, first dug a shallow 

 hole as represented at A, fig. 13; abandoning this it dug 



*Por description aud il.u.-^tration of tlio building of a nest and trap- 

 door by P. Caribivorus, see Amer Nat for July 1886. 



