Insect Powder. Camomille de Perse, Fr. Persische Bertramblumen, G. Pyrethri Flores.—The unexpanded or partly expanded flower-heads of several species of Chrysanthemum (Fam. Compositae). There are two principal commercial varieties: (1) the Dalmatian insect powder which is obtained from Chrysanthemum cinerariifolium (Trev.) Bocc., a perennial herb indigenous to Dalmatia and cultivated in the United States. (2) The Persian insect powder is obtained from the flowers of C. roseum Web. et Nohr and C. Marschallii Aschers, herbs growing in the Caucasus, Armenia and Northern Persia. The flowers are collected from plants that are from two to six years old, carefully dried and preserved. The most powerful insect powder is obtained from the closed or only partly expanded flowers providing they are properly dried and preserved.
Dalmatian Flowers.—The heads are hemispherical, about 12 mm. in diameter, and consist of a conical torus subtended by a straw-colored involucre and bearing upon the receptacle numerous yellow tubular flowers and a circle of cream-colored ray flowers. The latter are pistillate, the corolla being from 1 to 2 cm. in length, having about 15 delicately veined and 3 short, obtuse or rounded teeth.
Persian Flowers.—The heads are flattened top-shaped; the involucral scales are greenish-brown; the ray florets are reddish-brown or reddish-purple, attaining a length of 15 mm., being somewhat plicate and having 7 veins. The disc florets are tubular and yellow.
For details as to the special anatomical character of these flowers, see P. J., lxvii, 474; also J. P. C., 1902, xv, 409.
C. cinerariaefolium is now being cultivated on a large scale in California, and as more care is given to the preservation during drying of the color and of the volatile oil than in Dalmatia, the California product which is known by the name of buhach is said to be superior to the foreign drug. (C. D., August, 1889; see also for method of cultivation, Reports of the Fourth U. S. Entomological Commission, 1885, and papers by Seidler, Riedel's Berichte, 1913, and Juttner, Ph. Ztg., 1912, 817.)
The insect powder of commerce varies in color from yellow, yellowish-brown, or brownish-yellow to yellowish-green, the finer qualities verging towards brown and the poorer towards green. Brilliant yellow powder should be viewed with suspicion. On microscopical examination of an insect powder, it will be found to consist of fragments of involucral scales composed of sclerenchyma, perhaps bits of stems composed of collenchymatous cells, pollen grains, fragments of the corolla and of its epidermis and papillae. The absence or scarcity of pollen in the powder shows the absence or scarcity of the flowers in the drug, while the proportion of collenchymatous tissue indicates the proportion of stems. As the activity of the insect powder resides in the flower, specimens containing little of the flowers or much of the stems should be rejected. The powder yielded by the Dalmatian plant can usually be distinguished from Persian insect powder by the following characters. The outer surface and edges of the scales of the Dalmatian flowers contain numerous hairs, consisting of a long cell with attenuated ends placed horizontally upon a one- to three-celled stalk. The Persian flowers are almost entirely glabrous, a white hoariness being found only at and near the base of the scales, and very few hairs near the apex; the hairs are of the same structure as the preceding, only the terminal cell being much longer. Sclerenchymatous cells are much more numerous in the Persian than in the Dalmatian. The so-called Hungarian or Russian daisy, probably a species of the subgenus Leucanthemum, was at one time used as an adulterant. The importance of the adulteration is increased by the fact that the Hungarian daisy appears to be entirely free from insecticidal properties. The Hungarian daisy is distinguished from the true Pyrethrum by the orange-yellow disk florets, by the depression of the involucre, by its prominent dark receptacle, and by the absence of pubescence and pappus. The odor is less pungent than that of the true insect flower, being more like that of matricaria. The difference in odor is more pronounced on infusing in warm water. The Hungarian daisy yields a powder somewhat darker in color than true insect powder. Microscopically, the Hungarian or Russian daisy differs only in the absence from the involucre and stems of the peculiar hairs seen on the scales of the true insect powder, and the presence in their place of certain hairs, consisting of from four to ten cells, and terminating with a much elongated, thin-walled, or inflated cell. There seems to be no recognizable difference between the pollen of the two plants which yield insect powder and of the Hungarian daisy. The presence of quassia, fustic, turmeric, and other adulterants may be made out by the aid of the microscope, and chrome yellow chemically, but the powder of Hungarian daisy cannot be detected microscopically. According to George R. Durrant, however, the Hungarian powder yields 10 per cent. of ash, whereas true insect powder yields but 6.5 per cent. F. Dietze, after careful study, found that the best method of valuation of insect powder is based on the amount, appearance and odor of the extract obtainable by the use of petroleum spirits boiling under 55° C. (131° F.). With such menstruum true insect powder affords a bright yellow percolate possessing the odor peculiar to the drug. (See P. J., 1905, 902; also 1906, 891; Ph. Ztg., 1905, 871.)
E. H. Gane, 1910, reports that insect powder is adulterated with ground stems and not ground from flowers only, at it should be. One sample from one of the largest pharmaceutical manufacturing houses was composed wholly of ground stems.
Insect powder does not appear to be actively poisonous to man, though it is said to cause some confusion of mind in those who sleep in close apartments where much of it is used. Upon the insects, however, which are apt to infest the person of man and animals, as well as bedding and sleeping apartments, it acts very destructively, first stupefying and then killing them. It is scattered over the person, upon the beds, about apartments, etc., and is even employed as a dressing for ulcers and wounds to prevent the formation of maggots. It also answers for preserving dried insects and plants in cabinet collections. The powder, exhausted by alcohol, is harmless to insects. The activity of insect powder is due to a toxic principle called pyrethron, and an amber-yellow syrupy substance which is the ester of certain unidentified species. The flowers also contain 0.5 per cent. of a volatile oil and from 4 to 7 per cent. of several resins. (Fujitani, Arch. f. exper. Path. u. Pharmak, 1909, 61, 47, and Chem. Zentralblatt, 1909, 80, ii, 1153.) The ash content varies from 5 per cent. to 8.3 per cent. In a series of experiments, Riley has found that the fumes of the burning powder are very poisonous to insects, and for certain purposes afford a ready mode of application, but that generally an aqueous infusion is the best and cheapest preparation. It is also used now in the form of cones made by making a mass with mucilage of gum arabic, with the addition of a small quantity of potassium nitrate. After drying these are ignited like a fumigating pastile. Twenty-five grains stirred up in two quarts of water were sufficient to kill young cotton worms. The infusion soon spoils. The tincture and the alcoholic extract are both efficient preparations. The tincture (one part to four) has been especially recommended, diluted with ten times its bulk of water, by F. Jager, to keep off vermin from the human body. According to Maisch (A. J. P., 1869, 128), it is capable of causing a vesicular eruption like that produced by the poison ivy.