Handbook of Medical Entomology Part 48

[N] _Nitellia_, usually included in this genus has the apical cell petiolate. _Apollenia_ Bezzi, has recently been separated from _Pollenia_ to contain the species _P. nudiuscula_. Both genera belong to the Eastern hemisphere.

[O] The following three genera are not sufficiently well defined to place in this synopsis. In color and structural characters they are closely related to _Cynomyia_ from which they may be distinguished as follows. _Catapicephala_ Macq., represented by the species _C.

splendens_ from Java, has the setae on the facial ridges rising to the base of the antennae and has median marginal macrochaetae on the abdominal segments two to four: _Blepharicnema_ Macq., represented by _B.

splendens_ from Venezuela has bare genae, oral setae not ascending; tibiae villose; claws short in both s.e.xes; _Sarconesia_ Bigot with the species _S. chlorogaster_ from Chile, setose genae; legs slender, not villose; claws of the male elongate.

[P] _Plinthomyia_ Rdi. and _Hemigymnochaeta_ Corti are related to _Ochromyia_, though too briefly described to place in the key.

APPENDIX

HYDROCYANIC ACID GAS AGAINST HOUSEHOLD INSECTS

The following directions for fumigating with hydrocyanic acid gas are taken from Professor Herrick's circular published by the Cornell Reading Course:

Hydrocyanic acid gas has been used successfully against household insects and will probably be used more and more in the future.

It is particularly effective against bed-bugs, and c.o.c.kroaches, but because _it is such a deadly poison it must be used very carefully_.

The gas is generated from the salt pota.s.sium cyanid, by treating it with sulfuric acid diluted with water. Pota.s.sium cyanid is a most poisonous substance and the gas emanating from it is also deadly to most, if not all, forms of animal life. The greatest care must always be exercised in fumigating houses or rooms in buildings that are occupied. Before fumigation a house should be vacated.

It is not necessary to move furniture or belongings except bra.s.s or nickel objects, which may be somewhat tarnished, and b.u.t.ter, milk, and other larder supplies that are likely to absorb gas. If the nickel and bra.s.s fixtures or objects are carefully covered with blankets they will usually be sufficiently protected.

There may be danger in fumigating one house in a solid row of houses if there is a crack in the walls through which the gas may find its way. It also follows that the fumigation of one room in a house may endanger the occupants of an adjoining room if the walls between the two rooms are not perfectly tight. It is necessary to keep all these points in mind and to do the work deliberately and thoughtfully.

The writer has fumigated a large college dormitory of 253 rooms, once a year for several years, without the slightest accident of any kind. In order to fumigate this building about 340 pounds of cyanid and the same amount of sulfuric acid were used each time.

In addition to this, the writer has fumigated single rooms and smaller houses with the gas. In one instance the generating jars were too small; the liquid boiled over and injured the floors and the rugs.

Such an accident should be avoided by the use of large jars and by placing old rugs or a quant.i.ty of newspapers beneath the jars.

THE PROPORTIONS OF INGREDIENTS

Experiments and experience have shown that the pota.s.sium cyanid should be ninety-eight per cent pure in order to give satisfactory results. The purchaser should insist on the cyanid being of at least that purity, and it should be procurable at not more than forty cents per pound. The crude form of sulfuric acid may be used.

It is a thickish, brown liquid and should not cost more than four or five cents a pound. If a room is made tight, one ounce of cyanid for every one hundred cubic feet of s.p.a.ce has been shown to be sufficient.

It is combined with the acid and water in the following proportions:

Pota.s.sium cyanid 1 ounce Commercial sulfuric acid 1 fluid ounce Water 3 fluid ounces

A SINGLE ROOM AS AN EXAMPLE

Suppose a room to be 12 by 15 by 8 feet. It will contain 12 15 8, or 1440 cubic feet. For convenience the writer always works on the basis of complete hundreds; in this case he would work on the basis of 1500 cubic feet, and thus be sure to have enough. The foregoing room, then, would require 15 ounces of cyanid, 15 ounces of sulfuric acid, and 45 ounces of water. The room should be made as tight as possible by stopping all the larger openings, such as fireplaces and chimney flues, with old rags or blankets. Cracks about windows or in other places should be sealed with narrow strips of newspaper well soaked in water. Strips of newspaper two or three inches wide that have been thoroughly soaked in water may be applied quickly and effectively over the cracks around the window sash and elsewhere. Such strips will stick closely for several hours and may be easily removed at the conclusion of the work.

While the room is being made tight, the ingredients should be measured according to the formula already given. The water should be measured and _poured first_ into a stone jar for holding at least two gallons. The jar should be placed in the middle of the room, with an old rug or several newspapers under it in order to protect the floor.

The required amount of sulfuric acid should then be poured rather slowly into the water. _This process must never be reversed; that is, the acid must never be poured into the jar first._ The cyanid should be weighed and put into a paper bag beside the jar. All hats, coats, or other articles that will be needed before the work is over should be removed from the room. When everything is ready the operator should drop the bag of cyanid gently into the jar, holding his breath, and should walk quickly out of the room. The steam-like gas does not rise immediately under these conditions, and ample time is given for the operator to walk out and shut the door. If preferred, however, the paper bag may be suspended by a string pa.s.sing through a screw eye in the ceiling and then through the keyhole of the door. In this case the bag may be lowered from the outside after the operator has left the room and closed the door.

The writer has most often started the fumigation toward evening and left it going all night, opening the doors in the morning. The work can be done, however, at any time during the day and should extend over a period of five or six hours at least. It is said that better results will be obtained in a temperature of 70 F., or above, than at a lower degree.

At the close of the operation the windows and doors may be opened from the outside. In the course of two or three hours the gas should be dissipated enough to allow a person to enter the room without danger.

The odor of the gas is like that of peach kernels and is easily recognized. The room should not be occupied until the odor has disappeared.

FUMIGATING A LARGE HOUSE

The fumigation of a large house is merely a repet.i.tion, in each room and hall, of the operations already described for a single room. All the rooms should be made tight, and the proper quant.i.ties of water and sulfuric acid should be measured and poured into jars placed in each room with the cyanid in bags besides the jars. When all is ready, the operator should _go to the top floor and work downward_ because the gas is lighter than air and tends to rise.

PRECAUTIONS

The cyanid should be broken up into small pieces not larger than small eggs. This can best be done on a cement or brick pavement. It would be advantageous to wear gloves in order to protect the hands, although the writer has broken many pounds of cyanid without any protection on the hands. Wash the hands thoroughly at frequent intervals in order to remove the cyanid.

The operations of the work must be carried out according to directions.

The work should be done by a calm, thoughtful and careful person--best by one who has had some experience.

Conspicuous notices of what has been done should be placed on the doors, and the doors should be locked so that no one can stray into the rooms.

The gas is lighter than air, therefore one should always begin in the rooms at the top of the house and work down.

After fumigation is over the contents of the jar should be emptied into the sewer or some other safe place. The jars should be washed thoroughly before they are used again.

_It must be remembered that cyanid is a deadly poison_; but it is very efficient against household insects, if carefully used, and is not particularly dangerous when properly handled.

LESIONS PRODUCED BY THE BITE OF THE BLACK-FLY

While this text was in press there came to hand an important paper presenting a phase of the subject of black fly injury so different from others heretofore given that we deem it expedient to reproduce here the author's summary. The paper was published in _The Journal of Cutaneous Diseases_, for November and December, 1914, under the t.i.tle of "A Clinical, Pathological and Experimental Study of the Lesions Produced by the Bite of the Black Fly (_Simulium venustum_)," by Dr. John Hinchman Stokes, of the University of Michigan.

RESUME AND DISCUSSION OF EXPERIMENTAL FINDINGS

The princ.i.p.al positive result of the work has been the experimental reproduction of the lesion produced by the black-fly in characteristic histological detail by the use of preserved flies. The experimental lesions not only reproduced the pathological pictures, but followed a clinical course, which in local symptomatology especially, tallied closely with that of the bite. This the writer interprets as satisfactory evidence that the lesion is not produced by any living infective agent. The experiments performed do not identify the nature of the toxic agent. Tentatively they seem to bring out, however, the following characteristics.

1. The product of alcoholic extraction of flies do not contain the toxic agent.

2. The toxic agent is not inactivated by alcohol.

3. The toxic agent is not destroyed by drying fixed flies.

4. The toxic agent is not affected by glycerin, but is, if anything, more active in pastes made from the ground fly and glycerin, than in the ground flies as such.

5. The toxic agent is rendered inactive or destroyed by hydrochloric acid in a concentration of 0.25%.

6. The toxic agent is most abundant in the region of the anatomical structures connected with the biting and salivary apparatus (head and thorax).

7. The toxic agent is not affected by a 0.5% solution of sodium bicarbonate.

8. The toxic agent is not affected by exposure to dry heat at 100 C.

for two hours.