1916] Doiv — Plaster Casting Insect Burroics 71 



renders the delay of a second dangerous. If one would like to 

 essay a nest of Formica exsectoides from which, say, three bushels 

 of earth had been thrown out, it would take about ninety-six 

 pounds of plaster solution. This is only practicable by mixing, 

 say, eight ounces at a time and making nearly 200 separate pour- 

 ings, trying each surface hole before pouring the second install- 

 ment into the same hole. Thus the lowest levels would be filled 

 and later superpositions become easier. The smaller species of 

 ants can often be treated with a few ounces of plaster, but great 

 care must be taken as most of the galleries are nearly horizontal 

 and the entrance so small that the thread-like stream of .plaster 

 lacks the weight to force its way through the laterals. In such 

 cases, and in Cicindela burrows built on a sidehill with horizontal 

 entrance, I have succeeded by taking a wide bottomed paper cone 

 into which a considerable weight of plaster furnished by gravity 

 the force necessary to fill not only laterals on the level but even 

 those which rise several inches. 



A great obstacle to success is the resistance of the inhabitant. 

 The body of the "pepo" is almost as large as the neck of its hole 

 (Fig. 11).^ When she perceives the stream of plaster coming she 

 opposes her body to it, with the result that the plaster falls on all 

 sides of her insufficiently liquid to rejoin, and thus the cast is 

 almost always hollow, the victim either escaping or being buried 

 near the neck. If there are young in the burrow she resists to the 

 death. Everything in the burrow is caught in the surface of the 

 plaster. The Cicindela larva opposes its chitinized head to the 

 plaster flow in the same manner and often blocks it completely. 

 In such case the luckless one is hauled up with head imbedded in 

 solidified plaster, to be killed as an act of mercy. If the cast be 

 wholly successful the larva is either forced to the bottom or re- 

 mains imbedded in it, leaving the cast hollow beneath it. 



Often there adheres to the bottom an oval film, not of spun silk 

 nor discarded larval skin. I presume that this is the covering of 

 a pupa of a parasite and that the pupa of the beetle is naked. Mr. 

 Brakeley bred out some parasites, but he sent them, as was his 

 custom, to some scientist and never got back either specimen or 

 name. 



Ants do not make the same sort of resistance. Those which do 

 not escape via some other gallery are imbedded in the surface of 



1 All figures are reduced about one third from natural size. 



