234 Transactions. 



Art. XXV. — Notes on Jest. Life-history, and Habits of Migas 

 distinctus, a New Zealand Trapdoor Spider. 



By J. B. Gatenby. 



[Bead before the Wellington Philosophical Society, 7th June. 7577.] 



Plate XV. 



I have to thank Mr. P. Goyen for identifying this species, and also 

 Professor Kirk for his many kindnesses to me. 



Migas disti /ictus is a small black spider belonging to a genus which 

 includes two other species — M. paradoxus and M. sandageri. 



The Nest : its Parts. (Fig. 14 — a clay bank.) 

 Lid. or Trapdoor. (Fig. 9, a, b, c.) 



Measurements. — Taken lengthwise (for the lids of the adult speci- 

 mens are seldom exactly circular) (fig. 7, e), the lid measures § in. to 

 | in. ; taken across, it measures T % in. to fin. The lids always vary 

 in thickness. If a 7>est is located in a mossy bank, the lid is thick, so 

 that the surrounding growths will spread to the surface of the door. 

 If the lid is situated in a hard, bare, clay bank, the spider, not needing 

 to provide rooting-surface, covers the door with a thin cement layer. 

 A thick door is often \ in. through; a thin door often less than -^hi. 



Construction of Lid. — The adult's lid is a compound structure, con- 

 sisting of several layers. The number of layers is never less than two, 

 and seldom more than twelve. Where the bank is mossy, the layers are 

 generally two — viz., a thin silk layer and a thick earth layer. If the 

 locality is dry and poor in growths, the lid has one very thin cement- 

 clay layer on top, and from four to twelve separate silken layers (fig. 7, 

 a, b* c, d, e — stages in growth). 



Layers of Lid. — Many adult lids show a rough, layered upper surface 

 (fig. 7, e) caused by the enlargements of the door. Each silken layer is 

 thicker at the edges than in the centre, and appears in texture like a 

 piece of linen. The material for the top, or the earthy layer, is scraped 

 from near the nest, and fine stones and pieces of vegetation are fre- 

 quently mixed together with the earth; hence the door becomes very 

 inconspicuous. Where the bank is lumpy, doors are sometimes con- 

 structed from small, entire, irregular pieces of earth, cut fiat on one 

 side, and hinged. 



Situation of Hinge. — The tube of the nest is very seldom straight, 

 but enters the ground with a curve (figs. 9, 10, 13, &c). The hinge is 

 invariably situated towards the curved terminus of the tube. Fig. 13 

 shows the natural position of tube, the hinge being on top, and hence 

 the door always shuts with its own weight. The hinge is often with only 

 one layer, but the remaining layers (sometimes five in number) are 

 continued above the hinge itself with a little upward twist (fig. 9, a, just 

 above arrow). This silken projection only allows the door to rise to an 

 angle of 60°. Often the side near the hinge is sunken into the ground, 

 and a ridge hangs over the depression (fig. 9, b and c, near the arrow); 



