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Insects Injurious To Drugs.

(Section II, Part III.)


Other tomes: AJP1883

The introduction of this brief appended section on insects injurious to drugs into a text-book of materia medica, while an innovation, seems desirable to the author of the text-book on the ground of the importance of the subject. It is a fact that stored drugs are attacked by a considerable number of insects, and that a varying amount of loss from this cause is sustained by practically every druggist, wholesale and retail, in the land. If, by the acquiring of a little knowledge of the appearance and habits of these pests, and by the exertion required in a little preventive or remedial care, this loss can be lessened, the introduction of this section, which attempts to furnish the information necessary for the little knowledge and the little care, will be justified.

The necessary entomological knowledge of the pharmacist who would make some show of resistance to the insect enemies of his drugs may be limited to an acquaintanceship with these insect enemies, and a knowledge of the means of fighting them. As a basis for this acquaintanceship, however, it is necessary to glance hastily at the great class of insects in general. More numerous in species and individuals than all other animals combined, the insects are conveniently divided into several great groups or orders. All the butterflies and moths, whose wings are covered with fine scales, and who obtain their food by sucking the nectar from flowers, constitute one order; the beetles, with their horny fore-wings and their powerful jaws for biting, compose another order; the two-winged flies, of which the familiar house-fly is an example, constitute a third order; the ants, bees, and wasps, and some other highly intelligent insects are grouped together in a fourth order; the true bugs, as the chinchbug and squashbug, with their sucking beaks, are comprised in a fifth order; the grasshoppers, crickets, cockroaches, and katydids compose a sixth order; and, finally, the gauzy-winged dragon-flies, the short-lived May-flies, and the wonderful white ants constitute a seventh order. But a simpler division of insects into two great groups is that often made, for convenience' sake, especially by the economic entomologist; namely, a division made according to mouth parts, all insects in the adult stage having mouth parts fitted for biting or mouth parts fitted for sucking. It is evident at once that the pharmacist will be especially interested in the biting insects, the ones which can attack roots and leaves, and all dry preparations. There will be little opportunity for the sucking insects to injure the pharmacist's stores. The insects may be divided according to this distinction as follows: The orders containing the beetles, the cockroaches, the dragon-flies, etc., compose the group of biting insects; the orders containing the true bugs, the butterflies and moths, and the flies, compose the group of sucking insects; while the order of the ants, bees, and wasps, and the order of mites (which are not true six-footed insects, but are closely related to them) may be said to compose a third group, in which the mouth parts are arranged for both biting and sucking, or piercing and sucking.

But we can not thus dismiss certain of the sucking insects from our pharmaco-entomological consideration; for with wonderful adaptiveness, nature has arranged that the young of certain sucking insects shall be provided with jaws for biting. The common worm-like caterpillars, which are the larval forms, or young, of butterflies and moths, are familiar to all; most children know that the strong-jawed, foliage-eating "worm," now feeding so voraciously on the green leaves of plant or tree, will in time change into some beautiful four-winged butterfly or moth, incapable of injuring a green leaf, and taking its food only in dainty sips, by means of its sucking tubular mouth parts, from some bright flower. And most housewives know that the dreaded clothes-moth—little, brown, delicate flutterer—is, in its moth or winged stage, harmless to furs or woolens, but that the dreaded little white grub, with its sharp jaws and voracious appetite, which really does the damage, is only the young of the innocent-looking moth, and that the moth, after all, is not so innocent.

So, then, it behooves the pharmacist to keep an eye on not only those insects which all their lives are truly biting insects, but also on those insects, as the moths, which, while harmless as adults, yet in their young stages, with strong biting mouth parts, appear as ravaging caterpillars.

In setting out to fight an insect pest, the economic entomologist asks first, "What is it? Is it a beetle, or a fly, or a moth?" This question answered, he already knows much about it; whether, for example, it is a biting or a sucking insect; he knows in a general way what sort of damage it does and how it does it, and he knows, too, in a general way, what remedies are most likely to be effective in fighting it. But it is always better and usually necessary to know the exact life history of the particular pest he must fight; he must discover where and when its eggs are laid, how long it remains in the larval or grub stage, what are its times and places of feeding, and what are its favorite articles of diet. From this life history he can decide on the character of the remedy to be applied, and when and where the remedy can best be used. Therefore the pharmacist may wisely turn to his jars and boxes, his store-rooms and laboratories, and try to discover what manner and number of insects he is to array himself against.

[image:12476 align=left hspace=1][image:12477 align=left hspace=1]Referring to some of the more common and destructive pests attacking stored drugs, the mites (order, Acarina) may first be noted. The mites, commonly enough represented and known in the case of the familiar flour or cheese mite, are minute, rounded-oval, eight-legged insects, with the mouth parts arranged to form a piercing beak. The body is not divided into head, thorax, and abdomen, as is the case with other insects, but all these parts are coalesced or merged into a single mass. While many mites suck the blood from animals or the juices from plants, many others feed on "dry food." Among these are the flour and cheese mites, and sugar mites with soft, smooth, whitish body (see Fig. 263), and belonging to the genera Tyroglyphus, Rhizoglyphus, and Glyciphagus. Many species of these genera of mites, besides being found in sugars, meals, and other vegetable products in the store-room, attack dried animal remains, cantharides suffering severely from the ravages of several species of Glyciphagus (see Fig. 264). The presence of the mites in the cantharides jars is indicated by much powder and broken bits of the beetles gathering on the bottom of the jars. In this mass of powder and fragments can be seen with the naked eye many small, moving, whitish specks, the mites. These specks, examined under the microscope, will reveal the characteristic shape and appearance of the mites.

[image:12478 align=left hspace=1][image:12479 align=left hspace=1]The most abundant pest in the pharmacal store-rooms appears to be a small, brown beetle, Sitodrepa panicea, belonging to the family Ptinidae, a family whose members, in both larval and adult stages, feed on dead, dry vegetable and animal matter. This family comprises a number of small beetles, rarely exceeding a quarter of an inch in length, and usually brownish in color. A conspicuous and distinctive character is the hoodlike prothorax, the head being so bent or drawn back under it as to be almost concealed (see b, Fig. 265). Sitodrepa panicea, the especially abundant species of this family, is from 2 to 3 mm. long, with a brown, subcylindrical body. It is almost entirely covered with many fine, short, yellowish hairs, which, on the upper surface of the body, are arranged in parallel longitudinal lines; the upper surface of the body (strictly, only the wing-covers) is finely striated (see a, Fig. 265). The head is almost concealed by the thorax, the front margin of the thorax reaching to the eyes. The head is also bent strongly downward. The young, or larva, of this beetle is a small white grub with three pairs of legs, and strong, dark brown jaws. The grub when lying at rest usually assumes a semicircular position (see c, Fig. 265). They feed voraciously on the drug, grow rapidly, and, after two or three weeks, pupate, and soon change into the perfect beetle. The beetle also feeds upon the drug by means of strong biting jaws, and the females soon lay eggs, from which another generation of larvae, or grubs, hatch. The whole life of the insect is thus passed in the can or jar containing the drug. The presence of the pest is shown by the collecting of a considerable amount of powder on the bottom of the can or jar (if the drug is a root, stem, or leaf), and by the presence in the drug of many small holes eaten by the insects (see Fig. 266). Often the little brown beetles may be seen crawling about in the jar. If the drug is a powder, this is the easiest means of detecting their presence. Sitodrepa panicea is almost omnivorous in the pharmacal store-room. In the store-rooms of the department of pharmacy, University of Kansas, Sitodrepa panicea has been found feeding on such drugs as the following: Columbo, aconite, mustard, althaea, belladonna, poke root, ginseng, angelica, etc.

[image:12480 align=left hspace=1]Still other species of the family Ptinidae feed on drugs: Lasioderma serricorne, a small brown beetle very like Sitodrepa panicea, but more robust, and with the wing-covers smooth and not striated, although covered with fine hairs as in Sitodrepa, is not uncommon. The larva or grub is like the grub of Sitodrepa, and the habits are about the same. I have found Lasioderma serricorne attacking powdered ergot, and Prof. J. B. Smith, entomologist of Rutgers College, has found it attacking belladonna root. Plinus brunneus, another species of the family, which I have found attacking musk root, powdered senna, and powdered jaborandi leaves, differs considerably in appearance from the other two members of the family just referred to. It is slightly larger, being about 4 mm. long, and it has long, slender antennae or feelers which project forward from the head (see Fig. 267). The antennae of Sitrodrepa and Lasioderma are usually bent back upon the body. The body of Ptinus is not subcylindrical, but tapers toward the head, the head itself being much narrower than the body. Bostrichus dactilliperda, another member of the family Ptinidae, attacks sweet almonds.

[image:12481 align=left hspace=1]Another family of beetles which includes several drug-attacking species is the Dermestidae. To this family belongs the common buffalo bug (Anthrenus scrophulariacea) of the house. The Dermestidae comprise a number of beetles, mostly small, which feed on skins, furs, various dried animal substances, and, to some extent, on dried vegetable substances. Anthrenus varius, which I have found in jars of powdered cramp bark and fenugreek, is small, rounded-oval, with transverse black, white, and reddish-brown waved stripes (see a, Fig. 268). The grub differs from the larvae of the Ptinidae in bearing many long, bristly hairs (See c, Fig. 268). The adult beetle lives chiefly upon the pollen of certain plants, but the larva or grub lives indoors, and, feeding on rugs, woolen goods, collections of natural history, furs, hairs, and drugs, is a serious pest.

[image:12482 align=left hspace=1]Another family of small beetles, the Cucujidae, is represented among drug pests by several species of the genus Silvanus. The beetles belonging to this genus are about one-tenth of an inch long, light brown, flattened, and with antennae clubbed at the tip (see Fig. 269). I have found Silvanus surinamensis attacking almond meal, Silvanus advena feeding on aconite root, and another species of Silvanus attacking angelica seed, quince seed, bitter-sweet, senega root, hyoscyamus, pellitory root, etc.

A large black beetle, Tenebrio obscurus (family Tenebrionidae), is sometimes found attacking drugs. I have taken it in jars of parsley root. It is three-quarters of an inch long, dull black all over, with bead-like antennal joints, and with narrow, parallel, longitudinal ridges along the wing-covers. A small, shining, black beetle (genus Paromalus), belonging to the family Histeridae, has been found in powdered poke root. Two species of Ceutorynchus, small snouted beetles or weevils, infest poppy and other seeds. Another weevil, Calandra oryza, imported from Europe, infests rice and ground roasted acorns.

The beetles comprise the chief drug pests, but some other orders of insects are represented by a lesser or greater number of pests.

The Lepidoptera or butterflies and moths, while possessing, in the adult stage, mouth parts adapted for sucking, have, in the young stages, strong biting-jaws. The young are the well-known caterpillars, and may be distinguished from the. young or grubs of beetles by the number of legs. The larva or grub of the beetle has but three pairs of legs, and these are attached to the first three segments of the body lying just behind the head; the larva or caterpillar of a moth has, in addition to these three pairs of so-called thoracic legs, usually five more pairs of legs, four of these pairs being attached to segments in the middle region of the wormlike body, and the fifth pair being attached to the last segment of the body. The grubs of beetles sometimes have in addition to their three pairs of thoracic legs a single leg on the last segment of the body.

[image:12483 align=left hspace=1]Every one knows of the clothes-moth, dread foe of the housewife, which, as a small white caterpillar, living in a cylindrical roll or case (see d, Fig. 270) made from the woolen cloth or fur on which it is feeding, does irreparable injury to the choicest fabrics and costliest furs. This moth belongs to the genus Tinea, of which one or more species attack drugs. Fig. 270 illustrates the life history of the moths of this genus; c is the larva or caterpillar; b is the pupa or resting stage; and a is the adult moth. The moth is very small and light brown in color. I have found a Tineid attacking aconite root. Another moth, known as the Angoumois grain moth (Gelechia cerealella), attacks, in the caterpillar stage, all kinds of stored grain. It bores holes into the grain kernels and eats out the starchy interior, leaving only a delusive hollow shell. Figure 271 shows the appearance of the infested grain kernels. The larva of Carpocapsa amflana, a moth of the same genus as the codlin moth, the greatest insect pest of the apple, infests the seeds of Corylus avellana, Juglans regina, and Castanea vesca. The larva of Mylois ceratonia feasts on the fruits of Ceratonia siliqua and Castanea vesca. The larva of the moth Oecophaga olivella inhabits the kernels of the olive, causing the dropping of the fruit and a smaller yield of oil.

[image:12484 align=left hspace=1]Passing now to another order of insects, the two-winged flies, we find that while the mouth parts of the adult flies are adapted for sucking or lapping, the young flies, which appear as grubs or maggots, are in many cases better prepared to partake of solid food. The olive in southern France and Italy is infested by a larva of a fly known as Dacus oleae; in the kernels of fresh hazelnuts are often found the larvae of a fly which belongs to the same genus as that notorious wheat pest, the Hessian fly. The fly Trypeta arnicivora is often gathered in its youthful state with arnica flowers, and becomes developed later on, after feeding on the flowers in the pharmacist's canisters.

[image:12485 align=left hspace=1]The book-louse insects (genus Atropos) have at least one representative in the list of drug pests. I have found a species (probably divinatoria) of this genus attacking golden seal and hyoscyamus. The insect is very small, hardly a twentieth of an inch long. When examined with a microscope it is found to be wingless, and of a general appearance as shown in Fig. 272. This insect represents the family Psocidae, of the order Pseudoneuroptera.

[image:12486 align=right hspace=1]The order of wingless insects Thysanura, which includes the "fishmoths," those active scale-covered little creatures of the household, is represented by a member of the genus Lepisma (probably saccharina) (see Fig. 273), which I have found in jars of mezereon bark and Socotrine aloes.

[image:12487 align=left hspace=1]Finally, in jars of gall the pharmacist may find numerous little fourwinged, compact-bodied "flies," which are not, however, attacking his stores, but which are only the insects which produced the galls, now issuing from them. These little insects (see Fig. 274) are Hymenoptera, belonging to the genus Cynips. The pharmacist may find other Hymenoptera (distinguished by having four clear membranous wings with almost no veins in them, see Fig. 274) in his jars and cans; but these insects are his benefactors. They are parasitic on the beetles and other insect pests which are feeding on the drugs, and thus do much good. Their eggs are laid on the body of the grub of the drug-eating beetle, and the young hymenopteron, on hatching, eats its way into the beetle-grub and lives there at the expense of its host.

Remedies

Coming now to the matter of remedies, a reviewing of the notes thus far presented shows that beetles are the most serious and numerous of drug pests, and that practically only insects which have biting mouth parts are injurious. In fighting insects with biting mouth parts the common means employed by entomologists is to cover the substance attacked (usually the green foliage of plants) with a thin coating of arsenic, by means of spraying. In the nature of the case this method is out of the question in fighting drug pests, but, because the drugs are capable of being easily handled and subject to treatment in air-tight vessels, a very convenient, effective, and universally applicable method is possible, namely, treatment with vapor of bisulphide of carbon. The vapor of bisulphide of carbon is deadly to all insects in all stages, except the egg stage. The infested drug should be placed in a tight vessel (after having removed the dust and debris caused by the attacks of the insects) and a quantity of bisulphide of carbon, sufficient to charge the vessel with vapor, introduced. Any insect in the vessel will be killed. The remedy is simple, effective, and is feasible in the case of almost any drug.

Prevention of attack may be accomplished in some degree by the use of tight cases, though often the insects are introduced into the case with the drug, the drug specimens having come from an infested lot. Occasionally inspection of the jars and cans will detect the insects before they have had time to do much damage.

The ease of the detection of the presence of insects, and the ease with which the pests may be killed, makes it certainly worth the while of any druggist to devote a little time required for the effective prevention of insect damage to his stores.


A Manual of Organic Materia Medica and Pharmacognosy, 1917, was written by Lucius E. Sayre, B.S. Ph. M.



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