April, '09] JOURNAL OF ECOXOMIC ENTOMOLOGY 179 



alone will not suffice for food indefinitely. Animal food is also 

 required and we find that by supplying the colonies with a "balanced 

 ration ' ' of honey and fresh beef or veal, they will work in a perfectly 

 natural manner for many months without other food. 



The problem of confining the ants to the cage and its stand was not 

 so easily solved. We first tried Sir John Lubbock's method of plac- 

 ing a moat of glycerine or water about the stand, but both liquids 

 dried too quickly and were effective for only a few hours. Recourse 

 was had to the proverbial chalk line without success. Bands or 

 ditches of kerosene, crude oil. tar, oils of sassafras and citronella, 

 tree tanglefoot, zenoleum, naphthaline, coal tar disinfectants, whale- 

 oil soap, sharp-edged tin and fur were all failures. Certain powerful 

 odors, such as those of zenoleum, sassafras and citronella, act as 

 repellents temporarily, but after a few hours of evaporation are no 

 longer effective. Ordinarily these ants will not cross bands of cotton 

 tape which have been impregnated with a saturated solution of cor- 

 rosive sublimate and dried, but when attempting to leave an area 

 to which they have been confined by this means they are much more 

 persistent in crossing it. 



Water with a film of whale-oil soap on it acted as a repellent for 

 a few hours only. Avhile a fihn of kerosene upon water merely af- 

 forded a convenient floor upon which the ants could travel. The 

 difficulty in confining the workers with any liquid or mucilaginous 

 substance lies in the fact that they are exceedingly light- and sticky 

 substances shortly harden on the surface so that the workers are 

 supported. The surface film of clear water is in fact almost strong 

 enough to support a worker not loaded. It is not unusual to see an 

 ant alternately walking and swimming in crossing a narrow ditch 

 of water which has been standing for a few hours. ^linute dust par- 

 ticles collecting upon standing water shortly form a film upon which 

 the workers pass with ease. Perfectly fresh water therefore served 

 to confine the colonies to their cages and at first our observations 

 were made upon colonies in cages which were standing in dishes of 

 water. This, however, necessitated frequent changing of the water, 

 and observations were often brought to an abrupt finish by other 

 duties preventing the change, of water in the vessels at the right time. 



Our next step was to construct a small building, 10 x 30 feet, 

 equipped with benches having upon them galvanized iron trays 

 21/^ X 12 feet. 4 inches deep. In these trays the cages are placed 

 and by suitable connections running water 2 inches deep is kept 



"The average weight of oue worker is 0.0002077 grams 



