WAX GLANDS OF THE COCKROACH 571 



soluble in water, so that when water is added no precipitate 

 would be formed. On the other hand, waxes, when sunilarly 

 treated, yield smaller amounts of fatty acids and, instead of 

 glycerol, give a large proportion of alcohol of the CnH2n4-i series, 

 which is a solid body insoluble in water. Consequently, when 

 water is added to these, a distinct precipitate is formed. 



The greasy appearing material obtained from the cockroaches 

 was treated in this way. A small amount of pure beeswax was 

 similarly treated as a check. In both cases, after the two sub- 

 stances had been saponified and the liquid evaporated over a 

 Water-bath, a decided precipitate was obtained on the addition of 

 water, more heavy in the case of beeswax, no doubt because 

 more of the wax was present. It seemed, therefore, that the 

 material secreted on the outside of the cockroach was wax. 



In order to substantiate the preceding conclusion, a series of 

 solubility tests were made with the second portion of the chloro- 

 form in which the roaches had been dropped. These tests were 

 similar to those carried out by Hollande ('14) in his research on 

 the oenocytes of insects, when he demonstrated that the crystals 

 found in these bodies were wax crystals. In order to obtain wax 

 for these tests a few drops of the chloroform was placed on a 

 glass slide and then subjected to a current of air. By this means 

 the chloroform was quickly evaporated, leaving a small residue 

 of wax, appearing as a whitish spot on the slide. Slides thus 

 prepared were unmersed in the various reagents for periods vary- 

 ing from fifteen minutes to one-half hour. Observations were 

 then made to see whether or not the material had been dissolved. 

 Beeswax and wax from Pseudococcus citri dissolved in chloroform 

 were used as checks. The results are as per table, page 572. 



The saponification and solubility tests therefore clearly indi- 

 cate that wax is present on the body of the cockroach. There- 

 fore, because wax is present on the bodies of these insects and 

 glands are found in their abdomens resembling glands found in 

 other insects which are known to secrete wax, it seems conclu- 

 sive "that these modified hypodermal cells are true wax glands. 



