To sum up, the ovipositor when at rest goes round the abdomen. Starting at the base, on the lower surface, it runs round the belly from front to back and then returns from back to front on the upper surface, where it ends at almost the same level as its starting-point. Its length is 14 millimetres. (.546 inch--Translator's Note.) This fixes the limit of the depth which the probe is able to reach in the Mason-bee's nests. One last word on the Leucopsis' weapon. In the dying insect, beheaded, stripped of legs and wings, with a pin stuck through its body, the sides of the fissure containing the inoculating-thread quiver violently, as if the belly were going to open, divide in two along the median line and then reunite its two halves. The thread itself gives convulsive tremblings; it comes out of its scabbard, goes back and slips out again. It is as though the laying-implement could not persuade itself to die before accomplishing its mission. The insect's supreme aim is the egg; and, so long as the least spark of life remains, it makes dying efforts to lay. Leucopsis gigas exploits the nests of the Mason-bee of the Pebbles and the Mason-bee of the Sheds with equal zest. To observe the insertion of the egg at my ease and to watch the operator at work over and over again, I gave the preference to the last-named Mason, whose nests, removed from the neighbouring roofs by my orders, have hung for some years in the arch of my basement. These clay hives fastened to tiles supply me with fresh records each summer. I am much indebted to them in the matter of the Leucopsis' life-history.