42 



EMBRYOLOGICAL STUDIES 



Studies on the Embryology of Caniponotiis herculcamis 



var. ferrugincus Fabr. and Mynnica scabriiiodis 



var. sabuleti Meinert 



METHODS 



The eggs for the studies on the first species were obtained from two 

 large colonies of Cainponotus herculcamis var. ferrugineus which I 

 kept through the winter in large Fielde nests (Fielde, 1904). The 

 temperature of the laboratory in which they were kept was about 70 F., 

 and remained practically constant day and night. Each colony con- 

 tained one queen. The ants were fed on dead insects, insect larvse, 

 sugar water, pieces of lean meat, and the yolk of egg. The queens 

 began laying in December and January, and laid during the rest of 

 the winter. Sometimes I allowed the eggs to accumulate in the nest 

 until the first ones began to hatch and then killed the entire bunch, 

 thus getting all stages. The egg periods varied, but averaged be- 

 tween twenty-five and thirty days. Very often by the time the first 

 eggs began to hatch there were from one hundred to two hundred 

 eggs in the nest. Sometimes I removed the queen and a few work- 

 ers to another nest and removed the eggs each day, placing them with 

 other workers, in order to estimate the time. I found it a very diffi- 

 cult matter to get the later egg-stages in this way because of the fact 

 that the workers ate many of the eggs ; but it was necessary to have 

 the eggs with workers or with a queen in order to prevent their being 

 attacked by fungi. In order to remove the eggs or the queen, the 

 entire colony was first stupefied with cold. 



The eggs were killed and fixed in a saturated solution of mercuric 

 chloride in 35% alcohol to which had been added 2% of glacial 

 acetic acid. The solution was used at a temperature just below 

 the boiling point. The eggs were then transferred to 70% alcohol, 

 in which they were left until the following day, or later. While in 

 70% alcohol the embryos were dissected out from the membranes 

 surrounding* them by means of fine dissecting needles. This could 

 be accomplished, after a week or two of practice, with little difficulty. 

 The embryos were then stained in toto in Grenadier's alcoholic borax- 

 carmine, Delafield's or Ehrlich's hsematoxylin, or orange G, and then, 

 after decolorizing, carried up through the various grades of alcohol 



