When we discovered rubrocinctum in the straw–stack, we made many observations as to the position of the egg and the number and condition of the spiders. We found that the egg was always placed either on the side or the back of the anterior part of the abdomen. The number of spiders stored was, as we have already stated, from seven to fourteen. A fact that interested us greatly was the remarkable accuracy shown by the wasp in never selecting too large a spider for the calibre of the straw. Oftentimes it was an extremely close fit, but it could always be squeezed down. When they nested in posts they used at times much larger prey. Unfortunately we never saw this species capture its prey, nor could we prevail upon it to sting in captivity, but the number of spiders that we found in straws was so large as to afford abundant evidence concerning the degree of surgical skill possessed by the wasps. P. marginatus and P. scelestus, in overpowering their large fierce Lycosids, must sting when and where they can, but most of the spiders taken by rubrocinctum are inoffensive creatures, and there is so little need to be careful or adroit in dealing with them that she has time and opportunity to sting the exact spot that will give the best results. [Illustration: TRYPOXYLON RUBROCINCTUM] The concentration of the nervous system in the Arachnida would seem to conduce very strongly to uniform results from the stinging of the wasps. Unlike the larva used by Ammophila, with its chain of ganglia, in the Araneidæ the whole central nervous system, including the brain and the ventral cord, forms a single mass, pierced by the œsophagus. The greater part of this mass, which lies behind the œsophagus, represents the fused ventral cord from which the nerves radiate. It is evident that a thrust given in almost any part of the ventral face of the cephalothorax, or even on either side of the anterior half of its edges, would reach the nervous centre. With these facts before us let us turn to the notes made upon the condition of the spiders that had been stung and stored up in the nests of the straw–stack. By the “first cell” we mean the last one stored, which was naturally the first one opened. July 11. Opened a nest of _rubrocinctum_. The first cell contained fourteen live spiders with a newly laid egg. Some of the spiders were very lively, moving spontaneously. Second cell, ten spiders, one dead, others alive, and an egg. Third cell, eight spiders, three dead and five alive, and the egg. July 12. In each of the first and second cells one spider has died since yesterday, while in the third there is no change in their condition. The egg in the third cell hatched at nine in the morning, and the one in the second cell at three in the afternoon. July 13. In the first cell all the spiders are dead but one, and in the second, all but four, while in the third none are alive. July 15. All the spiders in the second cell are dead.