INSECT POWDER. 



45 



Fromme (86) reports the ash content of insect powder as being 

 between 6.5 and 9.5 per cent. In a hiter article (87) he criticizes 

 the method of Trottner in which the number of pollen grains in 

 1 milligram of powder is estimated, and the value of the 

 powder thus determined, the greater the number of pollen grains 

 the better the powder. Fromme determined the ash and ether 

 extract, observed the color and odor of the ether extract, counted 

 the number of pollen grains in 1 milligram of powder, and made 

 physiological tests with flies upon 7 samples of insect powder, with 

 the result that some of the most active powders were shown to con- 

 tain fewer pollen grains than other powders prepared largely from 

 stems. The analytical results on these 7 samples are given in Table 

 23. 



Table 23. — Examination of active insect powder (Fromme). 



Ash. 



Ether 

 extract. 



Per cent. 



Per cent. 



8.21 



6.37 



7.17 



6.00 



7.25 



6.15 



8.00 



5.85 



8.84 



6.27 



8.00 



5.01 



7.10 



3.40 



Color of other extract. 



Pollen 



grains In 



img. 



Golden yellow. . 

 Greenish yellow 

 Golden yellow. . 

 Greenish yellow 

 Golden yellow. . 



Dirty green 



Greenish 



308 

 2,415 

 2,900 



230 

 3,000 



710 



294 



SUMMARY OF METHODS. 



From the foregoing review of physiological, microscopical, and 

 chemical methods for determining the genuineness of commercial 

 samples of insect powder, it is seen that while satisfactory chemical 

 or microscopical methods have been developed for detecting the 

 addition of adulterants such as other species of flowers, curcuma, 

 and Pyrethrum stems, these methods are not capable of accurately 

 determining quantitatively the extent of this adulteration, although 

 the amount of stems can be approximated by comparing under the 

 microscope the unknown mixture with known mixtures of powdered 

 flowers and stems. Of course, the amount of an inorganic adul- 

 terant, like lead chromate, may be accurately determined by chemical 

 analysis, but such adulteration is now quite rare. Probably over 95 

 per cent of the adulteration of insect powder at the present time is 

 with ground Pyrethrum stems. 



One of the most promising microscopic methods for examining 

 insect powder thus far proposed seems to be that of Trottner, in 

 which the number of pollen grains in the weighed quantity of sample 

 is estimated. This number, however, varies so in different powders 

 of equal effectiveness as to prohibit a rigorous quantitative applica- 

 tion of the method. 



