The cork nests are the simplest form of nest, with the exception of those described above from Jamaica, and have constituted, up to the present time, the only type known in Europe. Their chief claims to our admiration lie in the perfection of workmanship which the doors usually exhibit, and the marvellous concealment which they afford when closed. These doors as a rule fit so tightly [thanks to the accurate adjustment of their sloping sides to the bevelled lip of the tube which receives them,] that they afford a certain amount of mechanical resistance, even when the spider is away. But, after examining a very large series of these cork nests, I find that there is some variation in the degree of perfection attained in their work by different individuals of the same kind. The mechanical resistance is greater or less in proportion to the thickness and weight of the door, and to the slope of its sides, and of the bevelled edges of the tube; and in each of these details a marked difference may be observed. One might suppose from what has so often been repeated as to the habits of _N. cæmentaria_, that, whenever any one attempts to open the door, the spider, which is always at home in the day time, would dart up from the bottom of the tube and endeavour to keep it closed by holding on from within. [Illustration: _Plate VIII._] I cannot say what may take place during the summer months; but from October to May I have but rarely found one of these spiders ready to oppose me, though _Nemesia meridionalis_ and _N. Eleanora_ frequently did so. Many times, wishing to provoke them, I have tapped at the door in order to apprise the occupant of my arrival, or lifted it and let it fall again, and always in vain, though the spider was there, crouching at the bottom of her tube. Indeed I can only recall six or eight instances in which this spider did hold down her door, and on three of these she was captured. I will now relate what I saw on one of these occasions,[65] for there has been much speculation as to the manner in which the spider clings to the door and offers the determined resistance which is experienced. [Footnote 65: Mrs. Boyle was the first to witness this curious sight, and my description of the resistance of the spider is almost an exact repetition of hers to me. It is curious also that, following her indications, I found the very nest and spider on which she had made her observations, and every detail recurred again though several days had elapsed between her visit and mine.]