Capítulo 1903

 

Comboio da São Paulo Railway atravessando a serra onde Lutz

descobriu a malária das bromélias (MN. BR. Fundo Adolpho

Lutz).

São Paulo Railway train crossing the mountains where Lutz

discovered bromeliad malaria (MN. BR. Fundo Adolpho Lutz).

Forest Mosquitoes and Forest

Malaria *

 

The beginning of my work on the subject of malaria and mosquitoes coincided with an epidemic of malaria which began to develop not far from São Paulo under exceptionally interesting circumstances several years ago. At that time, a second railway line was being built from this city to Santos. The most important part of the line, that on the “Serra,” runs from the coastal plain very slightly above sea-level to the top of the slope, the lowest point of which is 900 m high and is flanked by peaks which tower several hundred meters above it.

This chain of mountains divides the coastal strip from the plateau on which the capital of the state, the city of São Paulo, lies at 700 – 800 m of altitude. The railway cuts through a very steep mountain-side, entirely covered by forest and completely uninhabited. When seen from the sea, the range looks very high and sheer. A mountain railway had to be used. Both lines operate by cables. For the new line not only the rails and bed had to be laid but also five sheds for

the machinery and 1 a number of tunnels and viaducts were built. The latter were unavoidable because of the deep gulches and ravines, down which mountain brooks and streams carry off the abundant precipitation of this serra saturated with rain and mist. Owing to the steepness of the slope, small and large water falls are quite

common, but, as easily understood, there are no stagnant 2 waters, in the usual sense of the word.

The initial railway, built more than thirty years before, had aroused great interest among engineers and tourists on account of the cable-pulled trains. It is considerably shorter and consequently much steeper than the new line. Eyewitnesses told me that during its construction intermittent fever broke out among the workmen but that it disappeared completely after the work was finished. For many years, not a single case of malaria had been reported among the few families of workmen living along the line, nor among the large number of passengers, some of whom traveled daily up and down.

When work on the new line was started, several thousand labourers

were engaged and settled in “ranchos,” or sheds, 3 built in the forest,

along 4 newly-broken trails. Before long, a number of cases of

intermittent fever occurred among these workmen. The sheds5 located in the lower and considerably warmer sections were the most affected. However, during the hot months, the epidemic spread to the top of the pass. The number of patients was very high and it often happened that, in a few days, the majority of those living in the same shed were brought down with the fever. Owing to the benign character of the disease and the plentiful use of quinine, the loss of workdays was generally transitory. Relapses were very frequent, even after leaving the place, and occasionally cachectic and anemic conditions supervened; on the other hand, there were hardly any fatal cases.

The engineers, who did not stay overnight in the infected zone, were not affected by the disease, so far as I know.

I had the opportunity to examine a number of the sick workmen and to satisfy myself that the illness really was malaria. Most (though not all) of the cases were of the benign form, confirmed by microscopic examination, which showed large and rather sparse plasmodia. Only

in the lowlands, where the forest abuts on a marshy lowland,6 were there a few cases of tropical (estivoautumnal) fever. In connection with the latter, a species of Anopheles breeding in marsh-water was found. In the sheds or ranchos, the walls of which were not made of wood but of woven fibers, leaving plenty of fairly larger openings, no mosquitoes were found in day-time, although they were very troublesome in the evening and at night. They flow out in the early morning. As I had formerly seen elsewhere, this happens all the

more easily as 7 the twilight mosquitoes also have a swarming period at dawn, which I had already observed, under very interesting conditions, in Anopheles argyritarsis.

In order to gain a clear insight into the conditions of the epidemic, I decided to spend some nights on the spot. For this purpose, I chose a house located about mid-way on the old line, which belonged to an engineer who was a personal friend and whose wife had acquired intermittent fever there. The very first evening, which followed a very warm day, there flew in a large number of blood-sucking insects, while we sat by a lamp. Among them were Simulium pertinax Kollar,

some rather common Culicidae known as occurring there8 and a species, completely strange to me, characterized by the spotted wings and the peculiar, perpendicular, position it assumed while

biting. In spite of its small size and frail9 appearance, it proved to be

an extremely voracious blood-sucker, 10 which settled without

hesitation 11 12 or any preliminary buzzing on the persons present and

also on a little13 dog. Owing to its behaviour and to the fact that its bite was less painful than that of several other species, it is often not felt by some persons, so that this little mosquito, which flies especially at dusk, may easily be overlooked.

I immediately felt14 sure that I had found the mosquito I was looking for, although nothing was known at the time about the characters of the transmitters of malaria. When shortly afterwards it was discovered that they had to be looked for among the Anopheles, I was very pleased to see that the new species was also a member of that genus: It is the kind which was later described as Anopheles lutzii by Theobald and is one of the smallest and most delicate species of the genus. As I discovered subsequently, it has quite a wide distribution, limited, however, to the rain-forest of the maritime

range15 and some adjacent areas, into which it follows the waters

emerging from the mountains.16 I have specimens from a series of places in the zone comprised between Santos and Conceição, and, owing to the kindness of Mr. Schmalz of Joinville, in the state of Santa Catarina, from that region also. On the other hand, up to now,

it has not been found further inland.17

Having found the suspected species (justly so as proved later), it next became necessary to discover its breeding places. I already knew that large numbers of mosquitoes, belonging to species which do not occur elsewhere, swarm in all our damp woods; and also that on these steep slopes ponds and puddles are very rare. Therefore, I felt justified in expecting unusual peculiarities in the mode of life of the larvae. It could hardly be doubted that they were aquatic, like the other culicid larvae, so the problem really consisted in finding the right sort of water deposits. After some pondering on the subject, in the light of former experience, I arrived at the right solution.

I was already aware 18 that some plants are specialized for holding water, which in its turn, is used by other forms of life. While in Hawaii, I had observed that Freycinetia arnottii (Pandanaceae) regularly contained water that served as the constant and sole habitat of a small crustacean (Orchestia), which in form and size resembles Gammarus pulex.

In this country it is especially the epiphytic Bromeliaceae which accumulate water, which is occasionally used for drinking, but more often surprises naturalists, especially orchid-collectors, with unexpected and by no means always clean showers.

I was also aware of the fact that all sorts of small creatures occur 19 in the water of bromeliads and remembered that Fritz Müller had described an interesting Ostracode living in this water. It seemed natural that, if this form could survive and prosper in bromeliad-water, the larvae of mosquitoes should also be able to live in it. And

since20 bromeliads were very abundant in these forests, I set out to examine them, with high hopes.

At first I met with disappointment, 21 being quite unable to collect suitable material.

Although every tree a certain size displayed an impressive number of bromeliads on its large, more or less horizontal branches, even these were some thirty feet above ground and thus entirely out of reach. On the other hand, the water of felled trees had naturally

been spilled. 22 I found some bromeliads growing on exposed rock surfaces but they contained only tadpoles. If the mosquitoes did breed in bromeliads, a fact which was irrefutably proved subsequently, then they must do so well above our heads.

Later on, I was repeatedly successful 23 in finding more accessible bromeliads in the same zone and was able to examine the abundant

water obtained from them. 24 Many kinds of mosquito larvae were found and among them also that of the new species of Anopheles.

Nowadays, after many years of observation, I am able to assort 25 that true forest mosquitoes, almost without exception, breed in bromeliad-water.

Gradually, an appropriate technique for collecting and rearing the larvae was evolved, a short account of which may be useful. I shall begin with a few data on the bromeliads themselves.

The monocotyledonous family Bromeliaceae, the best know member of which is the pineapple, or Ananas, comprises numerous species, almost all of them from tropical America. Many kinds are found in the state of São Paulo, mostly growing as epiphytes. The leaves are sword shaped; in a few species they are as narrow as the blades of grasses, but in many others they are up to 10 cm in width. The length may surpass a meter, but more often it ranges from a few decimeters to half a meter. These leaves are generally disposed in a short and compressed spiral, with their maximum width already at the base. They thus form a central funnel, surrounded by a number of bag-like cavities, in the leaf cup, all of them retaining the water which runs down the trough-like concave inner side of the leaves. This water is preserved for long periods and does not generally dry out entirely except after unusually prolonged drought. Mostly the

heavy dew is enough to prevent total loss.26 It can hardly be doubted that both the water and the abundant humus which forms in it are useful to the plants.

The species that are of special interest to us belong to different genera, such as Vriesia, Billbergia, Nidularium, Aechmea, Bromelia etc.

Although the smaller species may also furnish good material, it is naturally the larger specimens which promise the greatest yield. Owing to their size, the investigation of these is, however, fraught with certain difficulties. By simply overturning the plant, a number of the cavities are emptied simultaneously and the water runs off in every direction. It is better to empty the plant onto a large piece of rubber-cloth but, even so, many of the larvae and nearly all the pupae remain inside, clinging to the leaf-surfaces. The best results are obtained by use of the following method: first of all, the long leaves are clipped with a pair of scissors or a sharp knife, so as to

leave only a stump as long as the span of one's fingers. 27 After that, the plant is carefully detached from its support and the water, which in large specimens may amount to over half a liter, is poured out.

Following this, the stump is rinsed into 28 a suitable container. When the rinse water is added to that poured out, together they contain the whole fauna, which can then be thoroughly worked over.

The water retained by bromeliad often contains many dead leaves, stalks and twigs and large quantities of very fine humus derived from them. Crustaceans (Ostracoda, Copepoda, Lynceides) are found in them, as well as the larvae of Tipulidae, Culicidae, Corethra, Chironomus and other similar nematocerans. Beetle-larvae and tadpoles also occur. Tree-frogs and terrestrial planarian worms like this habitat, which unites the advantages of terrarium and aquarium.

Part of its denizens 29 lives on the humus, which is enriched by the presence of numerous microscopic organisms (Rotifera, Infusoria, Diatomaceae, Desmidiaceae, etc.). Others, like certain aquatic

beetle larvae, prey on small animals. The larvae of Megarhinus30 cause great havoc among the small Culicidae. They must be kept separate and fed on larvae of no value.

The forms 31 obtained can be allowed to continue to develop in bromeliad-water. This should be poured into flat dishes and some green aquatic plants added, otherwise the Schizomycetes will multiply until they predominate and form thick mats. The living bromeliad leaves probably expel tiny bubbles of oxygen and thus keep the water fresh. This is very likely the reason why bromeliad larvae are rarely seen at the surface and prefer to lie at the bottom, on their backs, as if seeking air there, with the respiratory tube turned downwards. The same attitude is also seen among marsh-dwellers, but more seldom.

Most of the mosquito larvae living in bromeliads are of the Culex

type and very much alike, 32 differing mostly by the form of the respiratory tube and not rarely also by the colour. Almost all are distinctly blue, green, red or lilac. These hues, which are sometimes rather pale, seem to be dependent on the fat bodies and connected with the mode of life. If the larvae are put into a different environment they are apt to fade gradually. Similar colours are often observed among swamp-larvae, such as species of Anopheles and Uranotaenia, but they do not constitute specific differences.

A very pronounced red coloration is peculiar to two species of bromeliad-dwelling mosquito larvae, Anopheles lutzii and Megarhinus violaceus Hfmnsg. (purpureus Theob.) both very

different from other species. 33 The first has the Anopheles type, but it is more compact, that is shorter and broader. With increasing age it

becomes a deeper and deeper crimson red.34 The other species has a peculiar, somewhat cylindrical shape and very wide respiratory tube, which serves to differentiate it from Anopheles larvae, as surely

as does the proboscis of the corresponding 35 adults. This larva

attains the unusual size of 12 to 15 mm. The color appears as 36 in dots, whereas the pupa is more diffuse yellowish-red with a dark

coloration of the caudal fins. 37 Besides these two, a vivid red-colored Corethra larva is often seen. Its habits are very similar to those of the Anopheles larvae, but it can readily be distinguished by the shape of

the head. These larvae also may show some fading 38 if their conditions of life are changed.

The number of larvae found in each bromeliad varies from plant to plant, but it is hardly large enough to permit the supposition that the whole clutch of a female was laid in a single one. Large larvae of Megarhinus violaceus are always found rather isolated, but in other

species 39 also there are so few specimens per plant that the eggs must be distributed among several of them. In typical bromeliad-breeders only a few eggs seem to mature at a time, and which might

therefore be somewhat larger than average.40 I have observed Trichoprosopon nivipes lay its eggs on the water, one by one, as do Anopheles and Stegomyia fasciata, and never more than a dozen at a time. In this case, development was very rapid, but in Megarhinus violaceus it may take a long time.

The life span of most forest mosquitoes seems to be rather long since, even after prolonged periods of drought, numerous specimens, some of them very much battered, are found. I have kept Trichoprosopon nivipes alive for two months. If they do not have enough liquid, however, they become very sensitive to dry air, in which they only survive for a few hours. I have also seen them suck dew and pure water but they prefer it sweetened. Honey is an excellent food for these and most other mosquitoes, provided it is offered in such a manner as to avoid their getting stuck to it. For this purpose, a small piece of sponge, or cotton-wool, is soaked in honey and then enclosed in fine wire mesh; this is dried on the outside with blotting paper, so that the mosquitoes can only reach the honey with the tip of the proboscis. Bananas and dates, which I have used with good results for other mosquitoes, according to the process described by Bancroft, are less suitable for forest-forms. Many of them are very blood-thirsty and bothersome, such as Wyeomyia longirostris and luteoventralis, the bite of which is very painful, whereas Sabethes and Trichoprosopon seem somewhat shier; Culex serratus and confirmatus, on the other hand, and also the species of

Janthinosoma 41 are importune blood-suckers, which attack also horses and dogs and can even be set successfully on birds. W. longirostris easily pierces thick fur and on occasion clothes with its long proboscis.

In many forests, if one remains for some time, one is boldly attacked from every side, unless this is prevented, because the forest mosquitoes bite at any hour. This applies to Anopheles lutzii, although, like Culex confirmatus, it decidedly prefers the twilight. In the shade, or when the sky is overcast, the mosquitoes may appear in quite large numbers even during the warmest hours, in many places. Capture [them] by night with lanterns always yielded the same forms. Of the true bromeliad-breeders, I have never seen Megarhinus violaceus or Culex imitator in flight, nor yet the rare Culex ocellatus nov. spec., for which breeding has to be resorted to. If they do bite human beings and larger animals, this can only occur

at night. 42

It is also strange that forest mosquitoes first arrive almost one by one (evidently guided by the sense of smell as they seek out especially perspiring persons and animals), but gradually increase in number, until it would seem that the whole population of the woods had been aroused. This is probably what does happen as the mosquitoes gather even in places where not only the larvae, but even the

bromeliads are scarce. Sight undoubtedly plays no part 43 in this occurrence, but it appears that the buzzing noise can be reciprocally perceived at great distances. Sometimes even the males appear though they do not bite. I have, however, never witnessed mating, which, presumably, takes place only in the twilight.

All the species with bristles on the metathorax have a peculiar habit, similar to that of the Syrphidae, of hovering in the air, in the same spot, for a long time, with the elongate hind legs arched over the back. In good light, the white tarsi of several species, such as Trichoprosopon nivipes, Janthinosoma lutzii and Sabethes remipes, and even the light shimmering parts of the feet of Wyeomyia longirostris are easily distinguished. Other species are recognizable by their blue or green sheen.

While other mosquitoes usually hum around the ears of their victims, for a long while, the forest Anopheles descend swiftly and almost silently and are mostly only noticed after they have already bitten. Their small size and perpendicular position help them to go

unperceived.44

The species of mosquitoes with larvae living exclusively in bromeliads probably constitute about one fifth of the approximately forty species found in this region. If those which occasionally also breed in ponds are added, the proportion should be one third at least. To the first group belong the genera Wyeomyia, Sabethes, Trichoprosopon and perhaps Limatus, besides the species of Megarhinus, Anopheles and Culex indicated above; probably also Stegomyia sylvestris nov. spec., Janthinosoma lutzii Theob. and possibly musica Say. Culex confirmatus breeds often, but not exclusively, in bromeliads and this probably also applies to serratus Theob. and crinifer nov. spec., which are sometimes found among the forest forms and sometimes among the swamp mosquitoes. Several small species, for instance Culex humilis and atratus Theob. and pleuriscriptus nov. spec., are generally collected in marshy places, but they use the water-retaining plants growing there. Bromeliads found on dry soil and on rocks may also contain mosquito larvae, but I have not investigated them thoroughly.

I would like to mention specially that the Eriocaulaceae also include a few mosquito-harboring species. In one of them, growing in marshes and determined as Eriocaulon vaginatum Korn by Edwall, I twice found a fairly large number of larvae of Culex cingulatus Fabr.-

Theob. in association with small Cyclopids.45 The water in which the host plants were growing was absolutely devoid of mosquito larvae.

In this instance the protection afforded by a habitat free from the usual predators is obvious.

The number of individuals belonging to the species of mosquitoes breeding in bromeliads is enormous and in many places must greatly surpass that of those belonging to the other species. The forested areas are also quite extensive. Big lagoons of brackish water, swamps and river-land also favour the plague of mosquitoes, even if they are unsuitable as breeding-sites. The water assembled there stimulates the development of the bromeliads, which clothe the trees in the vicinity and cover the dry soil or marshy ground, in association with other water-retaining plants.

The importance of a thorough understanding of these conditions must not be minimized. The extermination of larvae living in epiphytes by the chemical agents usually recommended for this purpose hardly deserves mention and the possibility of total eradication of the bromeliads is equally remote. Generally speaking, the opening of clearings is the only practicable means available; it does afford a certain measure of protection against forest and river malaria, and has been tested several times in Brazil. In the determination of the malaria conditions of swampy country, the water-retaining plants must never be overlooked.

Circumstances similar to ours must occur elsewhere. I hope that the results of the observations described here will help to shed some light on the conditions which foster endemic malaria, in many places where they still remain obscure.

I shall end with a few remarks on the water-retaining plants which serve as breeding-places for mosquito larvae. The most common forms of reservoirs are those found at the base of broad leaves encircling stems, a morphological feature more common in Monocotyledons. The forest thistle, Dipsacus sylvester, may serve as an example of its occurrence in Dycotyledons. Sometimes it is the bracts that collect water, as in Heliconia. In Nepenthes and Sarracenia, the whole leaf, or its terminal part only, is transformed into a peculiar, pitcher-like receptacle. As for the water it may be derived from atmospheric precipitation, as in the Bromeliaceae, or secreted by the plant itself, as in Nepenthes. In some instances its origin is not readily apparent. At times both processes might

possibly 46 concur. The origin of the water seems, however, rather indifferent, in regard to its suitability as a breeding-site for mosquitoes, even when the fluid secreted is able to digest dead

organisms. 47 It is more important that the water, which need not to be all abundant, should be protected against total evaporation, that enough air and light be admitted and that it contain some sort of nutritive substances. Adaptation of the larvae is also only possible in plants that are not over scarce.

None of the European plants that I know fulfil these requirements, but in America there are at least two families which are suitable, as just shown. The North-American Sarraceniae ought also to be studied from this point of view. In other parts of the world, I would point out the Nepenthaceae and Freycinetia, both of which have a number of species in many islands and on some coasts of the Pacific and the Indian Oceans. On the other hand, the traveler's tree, Ravenala madagascariensis Sonn., so far as I have been able to study it here, is not suitable as a breeding-place for mosquito larvae, despite the very ample reservoirs, which are sometimes used for drinking, located at the base of the leaves. These cavities only communicate with the outside sporadically and, even then, through quite narrow apertures; the water found in them, which is very limpid, was always devoid of macroscopic organisms.

Whenever mosquito larvae are repeatedly found in water-retaining plants, it is also advisable to ascertain whether some of the species present are not exclusively adapted to this habitat.

São Paulo, September 16, 1902.

Illustrations

Fig. 1 – Aechmea tinctoria Mez, one of the most common epiphytic

bromeliads, which frequently contains mosquito larvae. The plant

may become 75 cm high.

From Martius, Flora Brasiliensis.

Fig. 2 – Nidularium ampullaceum E. Morr., a small epiphytic species

which, however, contains abundant water. Average height about 20

cm.

Fig. 3 – Cut through the central part of a large bromeliad, showing

the numerous water retaining cavities. From nature.

Fig. 4 – Eriocaulon vaginatum Körn., a Brazilian plant growing in the

marsh, which harbours mosquito larvae. Maximum length of the

leaves about 30 cm. From nature.

Fig. 5 – Freycinetia Arnottii Gaud., a water-retaining Pandanacea

from the Hawaiian Islands. A blooming branch of this enormous

creeper is shown, greatly reduced here. Length of leaf from 45 to 75

cm. From Sinclair, Indigenous Plants of the Hawaiian Islands.

Fig. 6 – Nepenthes gracilis Korth., an example of a pitcher-plant.

From Engler and Prantl, Die natuerlichen Pflanzenfamilien.

Fig. 7 – Anopheles Lutzii Theob., a true bromeliad-breeding species and transmitter of forest malaria. Length without the proboscis 3,5 to

4 mm, with the proboscis 6 to 6,5 mm. From nature.

 

* Originally published as “Waldmosquitos und Waldmalaria,” Centralblatt für Bakteriologie, Parasitenkunde und Infektionskrankheiten, v.33, n.4, 1903, p.282-92, with 7 illustrations. Written by Lutz when he directed the Instituto Bacteriológico de São Paulo, this article, dated Sept. 16, 1902, was again published on April 30, 1950 in Revista Brasileira de Malariologia, v.II, n.2, in Portuguese (“Mosquitos da floresta e malária silvestre,” p.91-100) and in English (“Forest mosquitoes and Forest Malaria,” p.101-10). The English translation was probably done by Adolpho Lutz's son, Dr. Gualter Adolpho. Fundo Adolpho Lutz (BR. MN., box 23, folder 85 bundle 6) keeps the typed originals of the translation and a copy of Revista Brasileira de Malariologia with several revision notes in pencil, by either Bertha or Gualter, showing the mistakes in the published copy. In the present edition, these corrections have been registered in Editor's Notes. “Waldmosquitos und Waldmalaria” was the topic of many reviews: in Great Britain, a long review (“Forest mosquitoes and Forest Malaria”) was published in Journal of Tropical Medicine, 1903, v.6, p.111-23. Bulletin de l'Institut Pasteur did not give the topic the same amount of attention to this fundamental contribution by Lutz (1903, n.1, p.183); reviews were also published in Archiv für Schiffs- und Tropenhygiene (v.7, p.339-40), Münchener medizinische Wochenschrift [v.50, n.6, p.264], Hygienische Rundschau [v.13, n.18, p.937-8]; Rif. Med. [v.19, n.15, p.418], as well as in Allgemeine Zeitschrift [für Entomologie], v.8, n.18-19, p.377, written by Paul Gustav Eduard Speiser. [E.N.]

1 In Revista Brasileira de Malariologia, the phrase “five sheds for the machinery and” was omitted. [E.N.]

2 In Revista, “standing”. [E.N.]

3 In Revista, “barracks”. [E.N.]

4 In Revista, “on”. [E.N.]

5 In Revista, “ranchos”. [E.N.]

6 In Revista, “plain”. [E.N.]

7 In Revista, the six previous words were omitted. [E.N.].

8 In Revista, “uninteresting Culicidae familiar from the place”. [E.N.]

9 In Revista, “dainty”. [E.N.]

10 In Revista, “greedy sucker of blood”. [E.N.]

11 In Revista, “the slightest hesitation”. [E.N.]

12 In Revista, “humming”. [E.N.]

13 In Revista, “small”. [E.N.]

14 In Revista, “immediately sure”. [E.N.]

15 In Revista, “mountains”. [E.N.]

16 In Revista, “serras”. [E.N.]

17 Durham (Thompson Yates Laboratories Report, v.IV, pt.12, p.534) states that he found Anopheles lutzii in Pará. This may be possible but his description does not tally with the characters of this species. The larvae of his form were looked for, in vain, in puddles. [A.N.]

18 In Revista, “I knew”. [E.N.]

19 In Revista, “little animals are found”. [E.N.]

20 In Revista, omitted phrase. [E.N.]

21 In Revista, “a rebuff”. [E.N.]

22 In Revista “Should I resort to felling a few trees the water would only be spilled”. [E.N.]

23 In Revista “ I succeeded”. [E.N.]

24 During this investigation I was greatly assisted by several friends. I am very grateful to Mr. Aehrigsmann and Professor von Wettstein for supplying me with samples of bromeliad-water, containing mosquito larvae, collected in several localities. Mr. Schmalz, of Joinville, was kind enough to raise a number of mosquito larvae found in bromeliads, which proved to be the same as the forest mosquitoes found here. I am also indebted to Messrs. Loefgren and Edwall, of the Geographical Commission of the State of S. Paulo for help with the botanical literature. [A.N.]

25 In Revista, “in the position to affirm”. [E.N.]

26In Revista, “evaporation”. [E.N.]

27In Revista, “about the breadth of a hand”. [E.N.]

28In Revista, “rised in”. [E.N.]

29In Revista, “ Some of its inhabitants”. [E.N.]

30In Revista, “ Megarhinus violaceus”. [E.N.]

31In Revista, “ species”. [E.N.]

32In Revista, “fairly similar”. [E.N.]

33In Revista, the six previous words were omitted. [E.N.]

34In Revista, “more and more deeply carmine”. [E.N.]

35In Revista, “respective”. [E.N.]

36In Revista, “is disseminated in”. [E.N.]

37In Revista, “diffuse and has a more yellowish tinge, with dark swimming palettes”. [E.N.]

38In Revista, “discoloration”. [E.N.]

39 In Revista, “forms”. [E.N.]

40 In Revista, “ripen at a time, and on average should be slightly larger”. [E.N.]

41 In Revista, “avid blood-suckers”. [E.N.]

42 Nearly forty years later, Professor Lutz and his daughter showed that Culex imitator bites bromeliad-dwelling tree-frogs, especially casque-headed forms from the maritime scrub. Lutz & B. Lutz., Ann. Ac. Bras. Sc., v.XI, n.3, p.250-2, 1939. [T.N.]

43 In Revista, “Vision can evidently not play any part”. [E.N.]

44 In Revista, “almost silently and thus may remain unperceived, owing to its small and perpendicular position. Mostly it is only noticed after it has bitten”. [E.N.]

45 Several parts of the original text were omitted from this sentence in the Revista original copy, where one reads Eriocaulon vaginatum Kernk and only Culex cingulatus. [E.N.]

46 In Revista, “may”. [E.N.]

47 After I had finished these observations, I read that Haberlandt had found living mosquito larvae in Nepenthes ampullaria and Rafflesiana. See Haberlandt, Eine botanische Tropenreise, p.37.