DEPARTMENT OE AGRICULTURE, N.S.W.

THE DOMESTIC RATS.

WITH SUGGESTIONS FOR THEIR CONTROL IN FIELD AND BARN.

The Brown rat (Rattus norvegicus) and the Black rat

(Rattus rattus.)

W. W. FROGGATT, F.L.S., Government Entomologist.

These two rats have been known under different names. The “ brown rat ” is better known under the name of Mm decumanm, and the “ black rat ” under the name of Mm rattm. Latest authorities, however, have changed their scientific names, and they are now defined as members of the genus Rattm, and the specific name of the brown rat, decumanm, gives place to norvegicm.

The popular name of “ brown rat ” is also now somewhat misleading for under domestic conditions it has developed into almost a black variety, which, however, is quite distinct from the true black species, Raitm rattm, though sometimes confused with it. Though closely allied both in structure and habits, they are two well-defined species. The brown rat lives in the basement of houses, frequents sewers, and is more of an offal feeder. It does not climb so well as the black rat, and it is more shy and retiring. The smaller black rat does not vary much in colour, and is considered more as a house rat. In Europe it is found frequenting the ceilings and walls of houses instead of the basements, and it is not fond of water as the brown rat is. The brown rat has been known under several popular names. It was called the “ Norway rat ” because there were so many on the timber ships coming to English ports from Norway and Russia.

In Great Britain, during the eighteenth century, they were often called Hanover rats, a term also applied by the “ royalists ” to King George and his German Court, because they all arrived in London about the same time. Though now widely distributed over the habitable globe, it is not 200 years since the brown rat first appeared in Europe. Previously they had lived happy and contented lives in the far east; some writers say in northwester» China, others place their original home in much more southern latitudes. Changed conditions of life, howpver, led to migration westward t 7W)

in the early part of the eighteenth century. Traversing the eastern steppes, great armies of brown rats from Central Asia crossed the Volga and invaded Russia in 1738. Like the rabbit trek from Victoria northwards, they probably had many ports of entry, because within a very few years they were all .over Europe. It is stated that they landed in Great Britain in 1738, but other authorities give 1750 as the date. All other references to rats in England (and there was a Royal rat-catcher among the Court officials in the days of Henry VIII, who wore a special costume), refer to the smaller and less pugnacious species, the black rat (Rattus rat tun) which is usually considered in popular natural history books to be a native of Britain. Recent investigations have proved that the black rat is also a native of the East. It is said to have accompanied the Crusaders home from Palestine in the middle of the thirteenth century; and it was probably n sponsible .for the outbreak of “black death” that followed the homeward path of the Christian armies.

The absence of indigenous rats in Britain is borne out by the fact that there is no word in the Welsh language for rat, and it is somewhat remarkable that, as far as the writer is aware, the rat is not mentioned in the Old Testament.

Ships are admirably constructed to spread rats all through the ports of the world, and with the spread of commerce even isolated islands soon become overrun with the pests. The recent very serious infestation of Lord Howe Island is a striking example of how rats gain a footing in isolated spots, and of the damage they can do where they have no enemies and where food supplies are unlimited. Until three years ago rats were unknown on Lord Howe Island, but at that date the s.s. “ Makambo ” had the misfortune to run on a reef, and all the cargo, in which some rats were evidently concealed, was stored on shore until she could be refloated. Since then the rats have increased into countless thousands; they are not only destroying all the bird fauna of the island, but they bid fair to destroy all the palm seeds, the collection and export of which is the sole support of the islanders.

There are many other interesting records of such island infestation. In the winter of 1797 a wrecked Norwegian ship drifted ashore at Suderoc, in the Faero Islands ; the rats effected a landing, and overran the group. Cats were impoited in large numbers, but a constant rat diet killed off the cats, and the rats are still in possession.

Early in the settlement of the Bermuda Islands, about 1820, some enterprising rats arrived in a vessel from Europe, and multiplied so rapidly that the whole group was soon infested, the rats swimming from island to island-Large numbers of cats were obtained, and soon after every rat vanished. The cats then became a pest, and some wise inhabitant imported stoats to destroy the cats, but the stoats preferred poultry and other game, and now the wri'er is told that the stoats and cats live in amity.

Rats were introduced into Mauritius. Their presence altered the history, of this island, for the Dutch settlers abandoned their plantations in disgust when the rats swarmed in. The French planters then took possession.

Boyle, in his work on Mauritius, says : “Hats are the bane of the planters; one resident informed me that he killed 40,000 rats annually on his estate, and the yearly damage to sugarcane was, at the lowest estimate, £10,000." St. Pierre says that they often eat all the maize in the fields.

Rats are a very serious menace to commerce and human life—first, on account of the millions of pounds worth of foodstuffs they destroy; and second, on account of their being the active agents in spreading bubonic plague. During the investigations regarding the outbreak in Sydney of

bubonic plague in 1909, all the first cases of plague development were traced to rats that had moved up into the city from the wharves, and to the infected fleas carried by the rats. One*of the difficulties in dealing with rats in a city like Sydney is that the water fronts are constantly being reinfested from the incoming ships. In spite of all precautions, ships are admirably adapted for protecting rats, and few ships are free from them.

The writer remembers the rat-infested coastal steamers of years ago where hungry rats even ate the soft kid and leather of boots left on the cabin floor. Though things are better now, and ships are regularly fumigated, there are

always some rats escaping, and in spite of all rope protections, if not acciden tally landed in open crates in the cargo, they can drop overboard and swim ashore.

The study of the balance of power and of the adaptability of animals to new surroundings or to changed conditions of life is very interesting to the    ^

economic zoologist. This is particularly so when we investigate the rat problem and the habits acquired by the rodents under domestic conditions.

The rat was once a wild woodland animal, at the mercy of its many natural enemies, such as ferrets, stoats, weasels, wild cats, and foxes, not to mention    «

the night-hunting owls and hawks. Living thus under natural conditions it was kept in check. When, however, it adopted man’s environment and made its home, first in barns and stacks, and finally in our houses, it found a comparative absence of enemies and unlimited food. Behind the wainscot of the drawing-room, hunting over the kitchen floor, feasting in the slaughterhouse yard, or swimming across the underground sewer, the rat is equally at home. He can eat through a lead pipe, excavate a passage under a brick foundation, climb along a slender rope, or nibble his way through a stout board without any great exertion, when hunting for food.

The fecundity of the female rat is remarkable. The young female breeds when she is 4 months old and before she is full grown. Though the first family consists of from three to five young ones, as she increases in age, if food is abundant, the more mature animal often gives birth to ten young ones, and there are records of fifteen or sixteen in a litter. The female breeds all the year round, and under normal conditions she has five or six families in the year. It is not, therefore, difficult to understand how, under suitable surroundings, rats increase and multiply until they often outnumber the inhabitants of our large cities, eating and destroying hundreds of thousands    ,

of pounds’ worth of food every year.

So acute had rodent infestation become in Great Britain and Europe during the war, that a Mouse and Rat Act was passed in England at the end of 1919. Denmark and other countries also enacted laws to deal with    <

these pests. Under the British Mouse and Rat Act, powers are given to local authorities to compel occupiers to free all premises within a prescriberl time under a penalty of £5. After twenty-four hours notice the local authorities can enter and take all reasonable action to destroy the rats, and then recover all reasonable expenses thus incurred. This act also applies to shipping, and proceedings are instituted by or with the authority of the Board of Local Authority. Inspectors are appointed, and under their instructions enormous numbers of rats have been destroyed in the different countries by the organisation of “rat weeks”; over a million rats were destroyed in a six months’ campaign. A«cording to Jennison, between August and December, 1904, 100,000 rats were caught in Copenhagen.

When cleaning up the city in 1908, 99;000 rats were destroyed, and after trapping ceased there was still a very large rat population in Copenhagen.

Jennison considers that trapping will only reduce rats to a certain distinct limit because it is only the active males and' young females that are

captured, thus leaving a much larger food supply and fetter conditions for the breeding female rats whose fecundity is increased. He strongly recommends the enforcement of the Rodier system, the capture of all rats alive, the destruction of all females, and the liberation of all males captured. The abnormal increase of the males would cause the remaining females to die out without breeding.

Numerous as rats are under present conditions, it is hardly conceivable how they would multiply if it were not for the fact that rats are cannibals-They not only eat all injured or sick brothers, but the old bucks eat also the young ones in the nests. Nature’s grim law of tooth and claw is what balances the power of reproduction.

Modern writers have estimated that the rat population of Great Britain and Europe is equal to the human beings, and that, taking the cost of their keep at Id. per day, the foodstuffs destroyed would total a value of £15,(XX),000 per annum at pre-war prices, or nearly double that at the present rates.

The damage caused by rats in Sydney, both in warehouses and private dwellings, must run into hundreds of thousands of pounds every year, and similar destruction of food is going on in the same proportion in every country town.

It is not only on account of the direct damage that the rat does in destroying food supplies that the rat should be hunted and destroyed by every means in man’s power. He and his parasitic fleas play a most important part in the spread of that deadly scourge of the East—bubonic plague. Infected by plague germs through his unclean surroundings, he is also infested with several species of fleas. These fleas suck up the germ-laden blood of their host and can carry the infection into the blood of the first human being they bite. When in an unhealthy condition rats seem to be more suitable hosts for fleas than healthy normal ones, but when the rats die the fleas leave their fur and find fresh hosts, often accidentally, in human beings who are working in infested areas. Therefore we have to fight both rats and fleas in times of bubonic plague.

The cleansing of the city of Sydney by the block system is one of the most modern methods of making a clean city, and the propaganda work against dirt, fleas, and rats, if persisted in, should make Sydney a very much moie difficult place for rats to flourish and multiply in. Every warehouse and shop is liable to rat infestation, and the structure of most buildings is admirably adapted for the rats. All new buildings should be constructed in such a manner that they are rat proof, and if the rats gain access from outside, each floor or room should be closed and fumigated and rats should not be able to get under the floors or into the roofs.

Rats are frequently carried into well-built warehouses in open crates, boxes, or bales or bags of skins. It would pay every warehouse owner to have a special quarantine basement room where all such goods could be opened and unpacked before being distributed all over the building. Thus

• in properly constructed warehouses all food supplies would be stored in rat-proof rooms, easily fumigated at a slight cost, and not only the rats accidentally brought in, but those that strayed in through open doors would be destroyed before they had done much damage.

Rats can be destroyed in many ways in our cities, but any crusade against rats must be universal, and all persons should be compelled to get into line with the civic authorities and sanitary officers if they will not do it of their own accord.

Trapping.    *

In the ordinary residence, rats are usually casual visitors, and can be easily caught with a horse-shoe bow or a break-neck trap if properly set and baited. When evidence of a rat’s presence is noticed in a house, all food and all scraps should be-carefully covered, so that no food is obtainable in either the house or the yard. One of the best baits the writer finds is a cube of freshly-roasted steak, fixed into the hook so that the rat cannot drag it off without using force; he has to tug the bait and thus releases the metal ring on the spring. A little grain or pollard scattered round on the floor where the rats come into the room for a night or two before the baited trap is placed in position, attracts the visiting rat to the same place, and, finding no loose food, he comes to the trap. A few drops of aniseed oil sprinkled at the trap, but not on the bait, also attracts the rat.

A number of different traps are on the market, but all will catch rats if properly set and baited, provided the hungry rats cannot get at any other unprotected food.

A hundred years ago, when ratcatchers were numerous, they used to work on a regular system in trapping. When operating in a family mansion, a ratcatcher would feed the rats in the basement in large double-ended traps, fixed so that the rats could run through them and find food and shelter.

When sufficient time had elapsed for all the rats in the neighbourhood to

find out where these free rations were being distributed, all the traps were    ,

set with no food outside, and rats came into the traps, but could not get out.

The catcher went round several times during the night and released the imprisoned rats into a receiving wire rat-trap, constructed for this purpose, and then reset tho double-ended wooden traps, and usually made a clean sweep of the rats in the one night.

The writer has a very old manual written by a professional ratcatcher over a hundred years ago. In this he gives the following formulas that are worth reproducing:—

No. 1 Formula—

20 drops of rhodium.

7 grains of musk. i oz. of oil of aniseed.

Shake the mixture well up, and anoint each end of the trap; dip a piece of paper in the mixture and drop it in the trap.

No. 2 Formula—

1 lb. of flour.

3 oz. of treacle.

6 drops of caraway seed oil.

Mix well up in a bowl, and then add 1 lb. of crumb of bread. (This was scattered about as the free rations for the rats before the traps were set. When baiting the traps the same mixture was used without the addition of the bread.)

Rats in Paddocks and Stacks.

The writer is especially interested, however, in rat and mice plagues in country districts, and those in our stacks of bagged wheat. At irregular intervals we have, in Australia, mice and rat plagues. These rodents appear in the country as if by magic, in armies of countless millions. Usually they start in the western scrub lands, travel eastward, and spread over the cultivated farms. They eat the maize and grain in the paddocks, and swarm into the stacks, granaries, and homesteads. The most notable and widespread mouse plague was that of 1917-18, when all the country railway sidings were covered with great stacks of bagged wheat in north-western Victoria and south-western New South Wales, waiting for transport to the ports. In this great area the mice took possession. They ate and destroyed at the very lowest estimate over £1,000,000 worth of wheat in New South Wales alone, and probably nearly as much in Victoria also. These mice were not counted when destroyed, but it was estimated by weight at Minyip, in Victoria, that 5) tons were captured in water traps in three days. At Berrigan, New South Wales, the ofiicer-in-charge killed over 40,000 every night for a week at the wheat stacks.

The most effective trap used at the wheat stacks was made in the following manner:—Four 9-feet sheets of galvanised iron were placed on edge to form a square, with a stout piece of pointed quartering driven into the ground in each corner to which the iron was securely nailed. Earth was then dug up and thrown against the outer surface until it was level with the top of the iron, sloping backwards and surrounding the square iron-screened pit. Kerosene tins, half full of water, were sunk level in the ground inside the trap at each corner, and a few pounds of wheat, or wheat and pollard, were thrown in the centre of the pit. The mice, looking for food, swarmed over the embankment and fell into the trap, and as they displaced each other they fell into the water tins and were either drowned or smothered as the tin filled up.

Such a trap could be moved and built up in a new area as desired.

In the inland districts from Tamworth in the north to Wagga in the south, mice and rats have appeared this present season. In some places the mice are most numerous; in other places, the rats are the pest. Both species have invaded the maize paddocks in the north, and everything is being

eaten out in some districts. The writer was informed that when other food was short even the young shoots of grass after rain were nibbled off by the countless swarms of mice..

In the country districts, one of the most effective methods of dealing with rat and mice plagues is poisoning with cyanide water, at the rate of 1 oz. of cyanide to 4 gallons of water. The cyanide water is placed in shallow dishes; roof guttering, if soldered up at the ends and placed in position in the ground, makes a handy water trough. All local water should be closed to the rats and mice sheltering in the stacks, outhouses, and fields. The dishes when first placed out should be filled with good clean water to which the rats and mice should have free access; when they have found the new supplies and have come regularly, say in four or five days, the clean water should be thrown out and the poisoned water placed in the troughs and dishes just before the first mice come out in the evening. The action of the cyanide is very quick, and the rodents do not get very far away after drinking. When the poisoning is finished, these dishes and guttering troughs should be very thoroughly cleaned, or, if much corroded, they should be burnt and buried.

Poisoning Rats.

The chief factor in successfully poisoning rats is much the same as that in trapping them. Get them used to coming to a certain place for food, and put out food for them in that place for several days before laying the poison baits. At the same time shut off all other food supplies, and see that no other food is left lying about the place. The more carefully this is done the more effective will be the destruction of the pest. The objection to the use of poison baits, particularly in a house, is that the poisoned rats very often manage to crawl away under floors and to obscure corners where they are very difficult to get at and remove. The smell from dead rats often makes it necessary to take up the floors.

Where rats can be poisoned without much danger of their becoming a nuisance, quite a number of poisons have been used effectively. Those poisons that kill rats most rapidly are the ones most in favour. It must be noted, however, that though the contrary is often stated, there is no poison that will dry up the body of a rat and render it odourless. It is always advisable to place a pan of water in the vicinity of any poison baits. Both rats and mice usually drink after eating, and drinking accelerates the action of the poison, and the aim should be to get a poison that acts rapidly before the rats can reach cover, and to spread it#in an open space so that poisoned rats can be collected and buried or incinerated.

Strychnine is one of the most rapid and deadly poisons for rats and mice in a house, and if the saucer containing the poisoned bait is placed in the centre of the infested room or basement, the victims will not get very far away. In the United States, where field rodents, such as ground squirrels, gophers, and many field rats, as well as domestic rats, are very destructive

on the farms, both dry and moist poison baits are used. The two following formulas are recommended in the United States Department of Agriculture Farmers’ Bulletin 670 :—

Dry Grain Formula—

1 oz. powdered strychnine.

1    „ bicarbonate of soda.

J ,, saccharine.

Mix thoroughly in a paper box and dust it over 50 lb. of crushed wheat ’    or 40 lb. of crushed oats in a metal tub (kerosene tin will do). This tin

should be burnt, and buried when it has been used up.

Wet Grain—

1 oz. strychnine sulphate dissolved in 2 quarts of boiling water.

Dissolve 2 tablespoonfuls of laundry starch in half a pint of cold water.

Add the strychnine solution, and boil for a few minutes until the starch is clear.

A little saccharine may be added, but is not essential.

Pour the hot mixture over 1 bushel of oat« in a metal tub and stir thoroughly. Let the oats stand overnight to absorb the poison.

As this bait is deadly to anything, besides rats and mice, that may eat it, all care must be taken when putting it out on boards, shallow dishes, or tins, that these receptacles are gathered up every morning and locked up when not out for bait.

Barium carbonate is a cheap and safe poison to use against rats and mice. J    Tt is stated to be harmless to stock and man, while most effective against

rodents; but Mr. Wright has pointed out that this is only partly true, and that any rat poison with barium as a component part should be kept out of the reach of children. He says : “ While carbonate of barium is insoluble in water, the acid secretions of the human stomach form soluble and poisonous compounds with this chemical, and hence may lead to fata results.” Barium carbonate is tasteless, and a bait containing from 2 to 2J grammes of it in 12 grains of dough will kill a rat.

The rat inspectors working under the Mouse and Rat Act, 1919, in tha different counties in England, have used the following formulas:—

No. 1 Formula—

6 oz.    barium carbonate.

4 „    dripping.

A „    salt.

16    „    meal.

This makes    1,000 baits    of    6    grains each, spread in pieces as large as a

hazel nut.

No. 2 Formula —

4 oz. barium carbonate.

4    „ biscuit meal or plain meal.

5    drops of oil of aniseed.

Mix with fat or dripping into pellets the same size as in No. 1 Formula.    *

No. 3 Formula—

50 per cent, tallow.

50 ,,    ,, barium carbonate.

Mix with dripping and spread as a paste on bits of bread.

Squills.—Another rat poison that has come into prominence of late years is sold under the name of “syrup of red squills,” of which there are various forms. This is made from the bulbs of Sci'la maritima, a seashore plant.

The powdered bulbs are also used.

The formula given by the English county inspectors, and which they claim has been very effective, is as follows:—

Red Squills Formula—

20 per cent, red powdered squills.

30    ,,    ,,    breadcrumbs.

30    „    „    fat.

20    „    „    syrup.

6    drops of oil of aniseed.

Crumble up the bread and mix the whole into a paste and cut up into    V

baits about the size of a hazel nut.

This bulb is poisonous to rats, but the raw bulb when chopped up soon loses its deadly qualities. Cooking the bait increases its keeping properties.    ,

Powdered bulbs are poisonous; of such powder 1 to 2 grains is the minimum charge for a bait for a full-grown rat.

Dr. Ferguson informs me that the Board of Health has used this poison, but it has been found very variable and unsatisfactory in its results. The present price, as quoted in the Chemist and Druggist, would render its use on, a large scale prohibitive in Australia.

Arsenic is one of the cheapest and most effective poisons in killing out many different pests. It has been largely used in food baits or in poisoned water for the destruction of rats and rabbits. As regards rats it has been found very variable in its action, and if rats recover from a dose they will not take another bait. Powdered white arsenic mixed with any suitable bait, at the rate of 1 oz. of arsenic to 12 of meal or pollard, and made with fat into baits or spread on bread is placed in their runs.

Phosphorus, mixed with pollard and other food baits, under many different names, is one of the chief poisons used with the poison cart for poisoning rabbits by station owners in their paddocks. The Sydney Health Department’s officers state that phosphorus paste is one of the best methods for poisoning rats in the city and suburbs, and in an outbreak of bubonic plague some years ago chip boxes of phosphorus paste were freely distributed to all householders. The present writer's personal experience was that most of his sample was eaten by the large cockroaches that visited his cellar.

All the approved poisons have been noted and described, but at present there seems to be a consensus of opinion that the use of barium carbonate has been so successful and the results so constant that it is the one that can be specially recommended. The fact that it is not poisonous to anything else but ground vermin, such as rats and mice, is also greatly in its favour. There is also a certain amount of danger when careless persons are handling strychnine or arsenic.

Poisoning can be carried out in the country with better results than in the house and store; but (as in the house) the more the food supplies are shut away from the pests, the more easy it is to poison the hungry rodents.

Fumigation for Rats.

A number of fumigants have been used in dealing with rabbits in their burrows in the country, and also in attacking the rats in ships, warehouses, basements, barns, stacks, and outhouses. In all places where gases and poison fumes can be safely used, fumigation is one of the most effective methods of destroying all kinds of pests.

Bisulphide of carbon, a heavy gas which sinks downward, is most effective in burrows in the ground, or in haystacks in the country, where the volatile liquid can be poured upon a piece of bagging and pushed into the burrow', or poked up holes in the stacks and closed up on the outside. The heavy fumes kill all the life that cannot get to the open air. This fumigant is Slso sometimes used by the city authorities to destroy rats in the sewers, and also in rat-infested ships; but on account of its inflammable nature wffien it comes in contact with a naked light, other heavy gases, such as carbon monoxide or sulphur dioxide, are more commonly used.

There is no danger to the operator from inhaling the fumes of bisulphide of carbon in the open, as there is with some other gases; but he must be careful not to allow any matches, pipes, candles, or naked lights to come in contact with the fluid or fumes, for they are very inflammable. A strong “ cabbage-water ” smell will warn the operator of the presence of fumes.

Carbon monoxide is rather dangerous, it gives no notice of its presence, and as the confined fumes are very deadly to human life accidents sometimes happen. It is chiefly used in the holds of rat-infested ships.

Sulphur dioxide, generated from burning sulphur, is the fumigant chiefly used in fumigating sewers and the holds of ships.

Hydrocyanic acid gas is generated by mixing cyanide of potassium with a combination of water and sulphuric acid. It is a very light and volatile gas, with great penetrative power. It is much used by entomologists on account of its power to penetrate through every crack and crevice, clearing houses of cockroaches, bugs, or insects that feed upon stored food products. The writer, while using it in Sydney warehouses, has frequently had practical evidence of its rapid effect on rats, and every rat enclosed in a fairly air-tight room properly charged with hydrocyanic acid gas is killed in a few moments, and usually dies in the open. Of course, the penetrative gas will also kill some in the roof, or those behind wainscots, but most of the dead rats can be easily collected and destroyed.

The writer considers that fumigation with hydrocyanic acid gas, under careful supervision, is one of the most effective, cheap, and rapid methods of destroying rats and mice in houses, and in any places which can be made reasonably air-tight so that the fumes can be confined for a few hours. The method is simple. The formula for every 100 cubic feet of space is as follows :—    "

3 oz. of water.

' 1 ,,    sulphuric acid.

1 „    cyanide of potassium.

Perfectly clean tins or earthenware jars or basins must be used as containers. These containers are placed at intervals in a room which has previously had all openings covered by pasting brown paper over them or plugged with bagging or other material. The operator will go round and measure the exact amount of water required for the charge and put it in the container. The cyanide, which has been broken up into small cubes, is then weighed, and the exact charge for each container is placed in a thin paper bag and placed beside the container. The operator then goes round with his measure and a jar of sulphuric acid, pouring the exact amount of acid into each container, taking care to pour it in slowly so that it shall not splash up on the hands and face, as it burns the skin. If by chance it does splash on the hands, place the hand at once in a tub of water and wash it off. As soon as all the containers are charged with the water and acid solution, the operator drops each package of cyanide into the container near which it is lying, starting at the one furthest from the door. The paper bag retards the development of the gas until he has time to complete the lot, leave the room, and lock the place up. The room must be locked up from the outside and left for the night. Next morning nearly all the fumes will have escaped from the building, and the doors and windows can be opened and the few remaining traces of the gas blown out. It is advisable to leave a window or two unlatched when they are pasted up inside, so that they can be pushed open. There is little or no danger for a careful man in fumigating any ordinary building.

In a cellar or basement where it might be difficult for the operator to get out quickly after the container is charged with acid, the bag containing the cyanide can be hung over the container by a string leading out through a hole in the door; the string can be cut or released as soon as the door is shut and the hole in the door then plugged up.

Cyanide of potassium has also been used like arsenic for making “ poison water baits.” The water to which the rats, mice, or rabbits are accustomed to come is shut off, and a fresh supply is set out near where they congregate. In two or three days they will have become accustomed to the new water supply, and then it can be all changed for cyanide water at the rate of 1 oz. for each gallon of water. This solution will retain its deadly qualities for about two days without deterioration, and be poisonous to a lesser degree for a longer period. The water can be placed in shallow pans or tins fixed in the ground. When available, lengths of tin guttering a few feet in length, soldered up at each end and Bunk in a furrow in the ground to keep them firm, will make ideal containers, and when done with they can be taken up and stored away for further use.

Infective Virus or other Micro-organisms.

It is well known that all rodents from time to time are carried off in large numbers by some virulent disease, particularly when the animals have increased in numbers beyond the normal limit. Micro-organisms that develop in the lungs, liver, or other organs, in the tissue of the body, or on the surface of the skin, such as hydatids, coccidiosis, and favus, all act in this direction. Some of our landholders have suggested that the Government should take this question up, and ask the Director of the Pasteur Institute to send a trained man to Australia to carry out investigations along this line.

The use of bacterial diseases for the destruction of rodents has been carefully studied, and many laboratory and field experiments have been carried out in Europe and America. Dr. Loeffer used Bacillus typhemurium in Thessaly to destroy the field mice in 1892-93, and claimed a certain amount of success, and other experiments were carried out in Russia.

In 1904 Danysz virus was used in France and very satisfactory results were, recorded, but generally speaking the. artificial production and use oi virus for rat and mice extermination has not been an unqualified success.

Hinton, in the British Museum Bulletin on rats and mice (Technical Series No. 8, 1920), says : “ The disease communicated usually propagates itself from rat to rat very slowly, and, what is worse, less than fatal doses render rats immune. The harmlessness claimed for all, towards animals other than rats or mice is, at least in many cases, open to question. Although bacteriology may furnish us any day with an efficient means of destroying rats at will, it cannot be said to have dope so yet. Not one of the many preparations sold can be recommended as a safe and thoroughly reliable means of destruction.”

While pointing out the unreliability of rat viruses as used in the United States, Lantz (House Rats and Mice, United States Farmers’ Bulletin 396) says : “ The chief defects to be overcome before the cultures can be recommended for general use are :—

“ 1. The virulence is not great enough to kill a sufficiently high percentage of rats that eat food containing micro-organisms.

“ 2. The virulence decreases with the age of the cultures. They deteriorate in warm weather and in bright sunlight.

“ 3. The diseases resulting from the micro-organisms are not contagious, and do not spread by contact of diseased with healthy animals.

“ 4. The comparative cost of the cultures is too great for general use. Since they have no advantages over the common poisons, except that they are usually harmless to man and other animals, they should be equally cheap; but their actual cost is much greater. Moreover, considering the skill and care necessary in their preparation, it is doubtful if the cost can be greatly reduced.”

Rat Fleas.

Dr. Ferguson informs me that three fleas are common upon the bodies of those rats captured in the city of Sydney and examined at the Board of Health in connection with the plague precautions :—(1) The common European rat flea (Ceratopsyllus fasciatus, Bose) which has been introduced into Australia from Europe with its host the rat; (2) the tropical or Indian rat flea (Xenopsylla cheopis, Roth) which has come to Australia with rats from the East; and (3) the mouse flea (Chenopsylla musculi) which ranges with its ordinary host, the domestic mouse (Mus musculi), from Europe and Australia, but which is also found upon rats. Other closely allied rat fleas that are not recorded in Australia are the Asiatic rat flea (Ceratopsyllus asinus Roth), which takes the place of our C. fasciatus in Japan and Eastern China, and the Javanese rat flea (Pygiopsylla analce), which chiefly lives upon rats in the plantations and is capable of carrying plague germs. Another African flea has been named Xenopsylla scopulifor; it is allied to X. cheopis, and is found upon rats in Eastern Africa. The chicken flea or sticktight flea (Echid-nopliagagallinaceus, West) is the chicken flea found in many parts of the world; it is very common in the United States where it has been given the popular name of “ sticktight flea,” because it is one of the species that buries its sucking mouth in the skin of the chicken, and, unlike the free roarping fleas, remains attached to its host. The generic name is rather unfortunate, but it was originally created by Skuse for a species found upon the skin of our Echidna, and when the fleas were reclassified the sticktight flea came naturally into this genus. Personally 1 have never seen this flea upon chickens in New South Wales, but Dr. Ferguson has recorded it as common in Western Australia. Another closely allied species (Echidnophaga myrmecobii, Rothsch), identified by Dr. Ferguson, is very common at times in the ears of rabbits.

Bishop says that in the United States the chicken flea attacks wild birds in addition to domestic species, and it has been taken on rats in numbers. It bites man with avidity. Two other species described by Baker (Ceratopsyllus cutus and Hoplopsyllm anomalus) are found upon the ground squirrels in the eastern United States. Bishop says : “ They have been shown capable of transmitting plague, and both feed readily on man, and will feed on rats.”

While rat fleas are true plague fleas, other fleas, such as the common house flea (Pulex irritans), and the cat and dog fleas (Ctenocephalus canis and Ct. felis), which are considered by some authorities to be the same species, are very serious pests in all parts of the world. Sometimes under suitable conditions for their development they appear in enormous numbers. Domestic cats in the house, and dogs which get under a house and sleep in the dry dust in such sheltered places, frequently become the generators of large numbers of fleas. Countless numbers of eggs are dropped in the dust under the house or upon mats of sleeping corners of domestic cats, and these places become ideal breeding grounds for fleas.

The tiny little eggs, like white crystal spheres, produce tiny white legless maggots, with a few scattered stiff hairs on the anal segments. These crawl into dusty cracks and crevices in the floors; they live upon dust, excrement, and dried blood. When full grown they form a regular cocoon in which they pupate, and from this cocoon the adult flea emerges.

Fleas are picked up in all sorts of public places—trams, trains, warehouses, churches, and in the streets—and are thence easily carried into perfectly clean and well-kept houses. When they obtain a footing in a neglected house where dust is allowed to accumulate or where cats and dogs can wander about, they may become a very serious pest.

Troubled with rats in a public building near the water front, the writer allowed the attendant to introduce two cats, and they were permanently located upon the same floor. When the warm weather came fleas appeared in all the rooms in thousands. They were traced to one room where there were carpets and mats upon the floor, and where the cats had taken up their abode in their leisure hours. The cats were got rid of, and a vigorous campaign was carried out against the fleas with kerosene sprays. Within a fortnight the building was clear of fleas once more.

Sydney: John Spe»oe, Acting Government Printer—1022.

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