232 GNATS OB MOSQUITOES — CHAPTER VIII which is murderous enough in Europe, is clearly no better in India, as it leaves a large surface unprotected just at the time when Mosquitoes are most persistent in their attacks. As regards children, mothers should deny themselves the pleasure of exhibiting their chubby limbs, at any rate in the evening ; but as little boys really look " sweet " in absolutely correct "sailor suits," with nautically cut but long pantaloons, there is no real difficulty in their case. The poor little girls, however, are again in a different case, as long stockings thick enough to be any good would cause unbearable irritation of the skin, and probably afford staphylococci the opportunity to start a most debilitating crop of boils ; and I fear it is no use pointing out that the "pantalettes" portrayed in Leach's drawings, in which their grandmothers disported themseves, would solve the difficulty ; unless indeed we can contrive to initiate a sort of Chippendale reaction for infantile millinery in their favour.
As a rule the Anglo-Indian has no alternative in the selection of his bungalow and must accept that occupied by his predecessor, or camp out. The better class of native gentlemen are beginning to see the superiority of the European plan of villa to such an extent that it is often difficult to find accommodation in what were once purely European quarters. So much is this the case that the provision of quarters built by Government is seriously mooted ; but I should be sorry to serve in India, even if housed in them gratuitously instead of compelled to rent them, as, owing to the high standard of work demanded by the department, the largest proportion of the money allotted for their construction will be required to secure technically perfect masonry, and a cramped heat trap, with no proper plinth or adequate through ventilation, but of beautifully pointed red brick, will necessarily result. There is a rule, perfectly reasonable, were it not rigid, that in such cases the rent must bear a certain proportion to the outlay, and that the former must be no more than a certain percentage of the average income of the occupants ; and probably a sufficiently healthy and commodious building, durable
CONDITIONS INFLUENCINC; PREVALENCE 233 enough for practical purposes, might be built for the sum, but the executive engineer would have no choice than to reject it if tendered him by a contractor.
There can be no doubt, however, that the provision of really healthy quarters for officials, as commodious as the large but ill-planned bungalows now obtainable, would be really a most remunerative investment even if the direct returns fell short of the requirements of the Accountant- General. Every station has its " Fever Hall, " most several, with generally no alternative accommodation ; and in one year I have seen three consecutive officers invalided from a fever trap of this sort, none of whom had the least desire to take leave, while the sum disbursed to them as ineffective pay would have easily rebuilt the pestilential hovel. Where, however, any choice can be exercised, a house with an upper story should be selected, as Mosquitoes never fly high, and even this amount of elevation affords considerable protection.
The writer once built, on the flat concrete roof of the house he occupied, a large grass hut, which was used by himself and family right through the rainy season as a sleeping apartment. Although fitted with punkahs, they were never used, as while our neighbours were sweltering through the night under them in the steamy, but sun-baked houses, we were able to obtain refreshing rest in spite of our Mosquito nets. This was long before the etiology of malaria had been solved, and the fact that we not only escaped fever but were all singularly healthy was a matter of constant wonder to them, as to sleep, in such a situation in the wet weather was looked upon as a certain invitation to fever. As a matter of fact, however, a hut of this sort, or a verandah, if deep enough to shelter from the drift of a shower, is not a bit damper than the inside of a house, and the only reason why to sleep in the latter is so notoriously dangerous is that they swarm with Mosquitoes more thickly than either within the house or in the open. Given adequate protection from the bites of infected Mosquitoes, it is far more healthy to sleep in such situations, and so gain refreshing sleep with comparative coolness and
234 GNATS OR MOSQUITOES — CHAPTER VIII the freest ventilation. Makeshift erections of this sort cost so httle in India that it is well worth making one, even if one can use it during but a short stay ; and I believe that a portable Mosquito room of the sort suggested, sheltered in a hut of this sort built on the roof where this is terraced, is the most practical plan of availing oneself of our new knowledge that I can offer. On several occasions we dined in our airy quarters, but though singularly free from Mosquitoes, the hghts attracted such numbers of other members of the insect tribes as to ill compensate for the gain in coolness. Mosquitoes exhibit a repugnance to almost all strongscented bodies, and almost every country has its own specific for warding off their attacks by their use. I have tried several of these reputed culicifuges and find that the most efficient are bodies such as kerosine and turpentine, which are as objectionable to the human nose as to the gnats. Celli (C. M., p. 207) gives the results of a long series of experiments with bodies of this kind, which clearly show that none of them are sufficiently powerful to be of any practical use for killing Mosquitoes, and I regard their value when employed about the person with the view of keeping them off as so small that it would be waste of space to further consider the question.
Relied on in place of a Mosquito net, they are worse than useless, as while they enable the user to get to sleep, their action is so evanescent that they leave him unprotected as soon as he has fairly landed in the land of dreams. For practical prophylaxis, the only use that can be made of them is to sprinkle them near persons sitting at table, and probably it very little matters what scent is used for the purpose, the ordinary cosmetics being as good as any. A good deal of protection, on the other hand, is undoubtedly afforded by smearing the skin with greasy substances, such as vaseline or oil, and I fancy that most of the culicifuge salves and ointments that are sold owe their value not to the scents, but to the fatty matter they contain. As a remedy for the smarting of gnat bites, I find nothing better than hazeline, and a mixture of eau de Cologne and water also affords considerable relief. As a rule, the direct
CONDITIONS INFLUENCING PREVALENCE 235 effect of the bites are too trifling to require treatment of any kind, but in some people they swell so much and cause irritation for so long a period that it might be worth while to try the use of weak tincture of iodine, which has recently been stated to abort the effects of the bites. One more point requires notice, viz., the suggestion thrown out by Drs. Stephens and Christophers that the European tropical resident should seek immunity from malaria by isolating himself from the native. The proposal to isolate the healthy instead of the sick is a novel one, and I must confess that it is difficult to understand how it is to be carried out, especially as in all such places the climate makes it impossible for the European to undertake his own domestic work, even if he possessed the leisure to do so, which is rarely the case, as his time is generally fully occupied in some occupation of a supervisory character. European and native alike reside in these insalubrious localities for the transaction of the everyday business of life, and it is useless to ask either to subordinate every business and social concern to the avoidance of one only of the numerous tropical risks that he has decided to brave. The native doubtless believes he could spare the company of the European, but the latter is absolutely dependent on the native for every necessity of comfortable existence, and would be in a miserable plight if deprived of his servants for even a few hours in the day. In India there is little to choose in degree of malarial infection between the two races, so that logically most of us would have to throw in our lot with our " Aryan brethren," and few but the last-joined "griffs" would be left to inhabit the sanitary oasis. Apart from this, in India at any rate, the declared acceptance by Government of the duty of bearing what Kipling calls "the White man's burden " would put the adoption of any policy, sanitary or otherwise, intended for the sole benefit of Europeans, entirely out of court, and I cannot beheve that the authorities of any of our other tropical dependencies would care to avow a different policy.
It is impossible to enter into a really exhaustive treat-
236 GNATS OR MOSQUITOES — CHAPTER VIII ment of the prophylaxis of malaria within the limits of a chapter like the present, or to notice all that has been written on the subject, even within the last twelve months, but it is hoped that the above sketch will suffice to give a general idea of the present position of the subject. In bringing it to a close, the writer trusts he may be absolved from the charge of holding extravagant views as to what can or should be done, and to avoid all misconception, would repeat that while he neither thinks it possible to exterminate Mosquitoes, or to do away with all malarial disease, he is convinced that, even with our present knowledge, it would be practicable to enormously diminish the number of cases in any given limited area taken in hand ; and further, though it is of course impossible to ensure safetj^, that anyone who will avail himself of a few by no means onerous precautions may greatly diminish his chances of becoming infected.
Since the above went to press, we have received good accounts of the practical work of the last expedition sent out by the Liverpool School of Tropical Medicine to West Africa ; and I have also received an interesting letter from Dr. Yale Massey, from Portuguese West Africa, in which he attributes a diminution of fever in his station to the filling up of pits left by building operations, and to the liberal use of quinine among the children.
237 CHAPTEE IX.
On the Distribution of the Culicidae.
The Culicidce are a truly cosmopolitan family, and may be found everywhere from the tropics to well within the polar circle. Their commonness indeed depends rather on the state of civilisation of a region than upon its geographical position. In new countries, in regions where the severity of the climate is such that they cannot support a sufficient population to undertake the complete drainage of the area, and amongst people whose civilisation, however old, has not reached the stage of "tidiness" and order, gnats and Mosquitoes will be found to be numerous and troublesome. As examples of this may be mentioned the cases of Lapland and the north-western portions of British America, where, during the short summer, they constitute a veritable pest ; so that, in the former country, the nomadic inhabitants are obliged to frequently change their grazing grounds to enable themselves and their herds to escape from their insect tormentors ; while in Manitoba, it is not uncommon for horses and cattle to be "stampeded" from the unbearable pertinacity of the indigenous species. In tropical countries again, the commonness of Mosquitoes is due far more to the difBculties of securing efficient surface drainage, and to the careless domestic habits of the people, than to any special favourableness of the climate. On the other hand, in countries such as England, Northern France and Germany, where centuries of human inhabitation have perfected drainage, and domestic neatness has reached almost to the position of a religious duty, gnats are so rare that, when they appear in any numbers, thej^ are commonly suspected of being a recent importation. Even in Holland, where the nature of the country appears to be entirely in their favour, they are by no
'238 GNATS OR MOSQUITOES— CHAPTER IX means so common as in many apparently less favourable localities ; for in Holland drainage is a primary necessity of occupation, and the domestic neatness of the people is proverbial.
With the exception of a few rarely visited islands, there are few parts of the world whence the Gulicidm have not been recorded, and indeed their constant association with man makes it almost impossible for any country that is much frequented to long escape their importation, as apart from their being carried in the larval state in ships' tanks, their habit of hybernation, and of harbouring in draperies while in that condition, makes their introduction a very easy matter.
Mr. R. M'Lachlan, in his notes on the insects of Captain Fielden's Arctic Expedition, mentions a species of Cidex, which, he says, may be C. caspius, Pallas, as identified by Curtis in the insects of Ross's Voyage (p. 66). Schiodle identifies the same species with C. nigripes, Zett. The latter, according to Staegel, occurs also in Greenland, and is the same as C. pipiens O. Fabricius, nee Linne {" Fauna Greenland," p. 201).
The late Professor H. N. Moseley, during the "Challenger " Expedition, described a species of " wingless Culex " from Kerguelen's Island (" Proc. Linn. Soc," XII., p. 578), but it is almost needless to say that the identification was a wrong one, as a wingless insect would not be a gnat.
In the beginning of the century, the " Nouveau Dictionnaire d'Histoire Naturelle," Tome VIII. , Paris, 1817, states that only some fifteen species, mostly European, of the family were known, but since then the number has steadily increased.
Schiner, " Reise der Novara," notes that 132 species of the family had been described (up to 1868). Of these 80 are European, 61 American, 21 Asiatic, 10 African, and 9 Australian, with one of unknown origin.
In 1889, Skuse estimated the number of described species at 160, including no less than 21 new Australian forms included in his paper ("S. A. C," p. 1,717); and subsequent
ON THE DISTRIBUTION OF THE CULICID^ 239 additions and the unearthing of many descriptions which had not been accessible to him, brought the number of descriptions collated in the first edition of this handbook to a total of 242 species, of which 18 belong to the genus Megarhina, 30 to Anopheles, 3 to Psorophora, 3 to Sabethes, 160 to Culex, 13 to Mdes, 12 to Corethra, and 3 to Mochlonyx.
Of these 72 were European, out of which 24 were recorded from England ; 20 from continental, and 29 from the islands of Asia ; 41 from North, and 36 from South America ; and 29 Australian. No better illustration of the small attention that had hitherto been devoted to the group can be given than the fact that but one species had been originally described from India, and that but four were recorded as having been found within its limits, putting aside the species and records appearing for the first time. It was obvious on comparing the various original descriptions then brought together for the first time, that on the one hand, many of the descriptions were so inadequate that they might easily correspond in the few particulars mentioned to a whole series of perfectly distinct species, while on the other, it was equally clear that many must be mere synonyms. It is, however, most dangerous to dabble in questions of synonymy unless one can compare the actual types, or at the least has available a large collection of locally-taken specimens, and in reality, no collection of the family worthy of the name existed ; and I therefore, with one or two exceptions, confined myself to a guarded acceptance of the efforts of others in this direction, most of which I may remark, would, it appears, have better been left unnoticed, as they have generally turned out to be wide of the mark, and to have merely added to the existing confusion. While I strongly suspected that many of the names enumerated in the systematic portion of the book were nothing more than redescriptions of species already known, it was equally obvious that the determination of the gnat fauna of vast regions of the globe was practically untouched, and that, as a necessary corollary, a large number of unknown species must remain to be discovered and des-