The mud nests made by females of Auplopus takachihoi in stone cavities each consist of 2-14 cells in plates masked by a common layer of clay 2-9 mm thickness. The female spends 90-130 min constructing each cell. and from 4 to 14 days in constructing and prey provisioning the entire nest. The nesting period is 10-20 days. The females prey on the spider Clubiona japonica L. Koch. 1878 (Clubionidae), paralysing them, amputating their legs and transporting one spider for each cell in which an egg is laid. The behavioural sequence of A. takachihoi is as follows: constructing nest-cell - hunting - paralysing - transportating ovipositiing - cell closure. The larva grows in 7-10 days and over-winters in a double-layer cocoon as a prepupa. The following season the imago emerges on average from 50% of the cells. The ichneumon wasp Caenocryptus sp. (Ichneumonidae, Cryptinae) is a parasite on the larva. Other aspects studied included diurnal activity, concurrent relationships between conspecific females, reaction of the wasps to human intervention, and the ejection of poison by the female as a defence mechanism. none