Bulletin No. 25— New Series.

U. S. DEPARTMENT OF AGRICULTURE.

p. sjfi 7

DIVISION OF ENTOMOLOGY.

N O T E 8

ON

THE MOSQUITOES OF THE UNITED STATES:

GIVING SOME ACCOUNT OF THEIR STRUCTURE AND BIOLOGY,
WITH REMARKS ON REMEDIES.

BY

L. (). HOWARD. Ph. I).,

Entomologist.

WASHINGTON:
government printing office.
1900.

Bulletin No. 25— New Series.

U. S. DEPARTMENT OF AGRICULTURE.

DIVISION OF ENTOMOLOGY.

NOTES

ON

GIVING SOME ACCOUNT OF THEIR STRUCTURE AND BIOLOGY,
WITH REMARKS ON REMEDIES.

BY

L. O. HOWARD, Ph. D.,

Entomologist.

WASHINGTON:

GOVERNMENT PRINTING OFFICE.
1900.

DIVISION OF ENTOMOLOGY.

Entomologist: L. 0. Howard.

First Assistant Entomologist: C. L. Marlatt.

Assistant Entomologists: Th. Pergande, F. H. Chittenden, Frank Benton.
Investigators: E. A. Schwarz, D. W. Coquillett.

Assistants: It. S. Clifton, Nathan Banks, F. C. Pratt, Aug. Busck, Otto Heidemann,
A. N. Caudell, J. Kotinsky.

Artist: Miss L. Sullivan.

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LETTER OF TRANSMITTAL

U. S. Department of Agriculture,

Division of Entomology,
Washington , 1). C. , July 1000.

Sir: I have the honor to transmit herewith manuscript of a bulletin
on the mosquitoes of the United States, which gives some account of
their structure and biology and indicates the differences in all stages
of existence between the kinds of mosquitoes which have been shown
to transmit malaria and those which do not. It also treats of the sub-
ject of remedies in considerable detail. It has been written mainly
from the popular standpoint, although scientific details of structure
and classification have been inserted for the use of physicians engaged
in studying malaria. I recommend that it be published as Bulletin No.
25, New Series.

Respectfully, L. O. Howard,

Entomologist.

Hon. James Wilson,

Secretary of Agriculture.

INTRODUCTION.

A number of articles and notes concerning mosquitoes have been
published in different bulletins of this Division. The most extensive
was the leading article in Bulletin No. 4, New Series (“The Principal
Household Insects of the United States”), and constituted the larger
part of chapter 1, on “Mosquitoes and Fleas.” In this treatment of
mosquitoes the complete life history of Oulex pungens was given, based
upon original observations made in the summer of 1895, and some gen-
eral remarks on the subject of other species were brought together.
Four pages were devoted to the subject of remedies, and the mosquitoes
of the country at large were tabulated, with such notes on geographical
distribution as could lie brought together. The earlier notes pub-
lished by the Division, including those extracts from correspondence
and general notes which had been published in the seven volumes of
Insect Life, and the writer’s two articles on the use of kerosene against
mosquito larva?, were all digested in this bulletin, which was published
in the summer of 1896. Subsequent brief notes on remedies have been
published by the writer in miscellaneous bulletins of the Division and
in the Scientific American, and the life history of Anopheles quadrima-
culatus was described, in comparison with that of Oulex pungens, in a
short illustrated article in the Scientific American for July 7, 1900.

The writer first became interested in mosquitoes thirty years or
more ago, when as a bojr he fished and collected insects in the marshes
at the head of Cayuga Lake, New York, and as early as 1867 had
experimented with the kerosene remedy against mosquito larva? in a
horse trough at Ithaca. In 1881 he discussed with Dr. A. F. A. King and
the late C. Y. Riley the bearings of the theory, which Dr. King was
the first to bring forward in the United States, of the probable rela-
tion between mosquitoes and malaria, both Dr. Riley and the writer
contending, it must be confessed, that the arguments brought forward
by Dr. King in conversation were based upon coincidental observations,
and afforded no good proof of cause and effect.

The writer’s practical demonstration in 1894 of the value of the
kerosene treatment as a practical large-scale remedy attracted consid-
erable attention to the subject of remedies for mosquitoes, and many
large-scale experiments were made, some of them being successful to
a marked degree, as will be pointed out later in the section on rem-
edies. The services of the members of this office force were called

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into requisition on a number of occasions to determine actual breeding
points in mosquito-infested regions, and interest in the subject grad-
ually increased until, during the past two or three years, the researches
of those medical men, whose names have since become so well known
in this connection, showed by exact methods that Dr. King’s theory
must no longer be considered a theory but a demonstrated fact. It
has resulted that the attention of the entire civilized world has been
drawn with vivid interest toward the whole mosquito question. Every
fact concerning mosquitoes becomes now of great potential importance.
The correspondence of this office on mosquitoes, owing largely to its
publications, lias become greatly increased. The writer has been
invited to address scientific bodies and citizens’ improvement associa-
tions on the subject of mosquito extermination, and in the spring of
the present year lectured before the annual meeting of the Royal
Society of Canada and before the section on theory and practice of
medicine of the American Medical Association on the subject of the
biology of the mosquitoes of the genus Anopheles as contrasted with
that of the mosquitoes of the genus Culex. The demand for the pub-
lications of this Division on mosquito subjects has been so great that
it has been deemed desirable to bring together the published and
unpublished articles and notes in convenient reference form from the
standpoint of the United States only, and this has been done in the
present bulletin.

The writer is indebted to his assistants, Mr. D. W. Coquillett, for
determinations of the different mosquitoes discussed; Mr. F. C. Pratt,
for untiring efforts in the collection of material; Mr. August Busck,
Mr. R. S. Clifton, and Mr. J. Kotinsky, for assistance in laboratory
experiments, and Miss L. Sullivan, for the preparation of the illustra-
tions. Information and specimens derived from many correspondents
are acknowledged in the pages of the bulletin.

L. O. H.

CONTENTS.

Page.

On mosquitoes in general 9

Abundance of mosquitoes 9

Alaskan and other far-northern mosquitoes - 10

Length of life of the adult mosquito 11

Life history of mosquitoes in general 12

Food of adult mosquitoes 12

How far will mosquitoes fly? 13

Carriage of mosquitoes by railway trains 14

How long can the lame live out of water? 15

The number of species of mosquitoes 17

Mosquitoes and malaria 17

Synoptic tables of the North American mosquitoes 18

Generic synopsis 19

Genus Culex 19

(a) Recognized species 19

(b) Unrecognized species 20

Genus Anopheles 21

(a) Recognized species 21

(b) Unrecognized species 21

Genus Psorophora 22

Genus Megarhinus 22

Genus Aedes 22

The biology of Culex, with remarks on some of the species 22

Life history of Culex pungens 22

Remarks on other species of Culex 28

The distribution of the species of Culex in the United States 29

The biology of Anopheles, with general remarks 31

Life history of Anopheles quadrimaculatnx 32

The adult 32

Resting position 33

Note of female 34

The eggs 35

The larva 36

The pupa 40

Natural breeding places of Anopheles 41

Other species of Anopheles 43

Distribution of the species of Anopheles in the United States 44

The genus Psorophora 45

The genus Megarhinus 47

The genus Aedes 47

The natural enemies of mosquitoes 48

Remedies against mosquitoes 49

Remedies in houses and prevention of bites 49

Remedies for bites 51

7

8-

__ # age.

Destruction of larvae and abolition of breeding places 5]

Kerosene on breeding pools 51

Drainage 53

Practical use of fish 54

Artificial agitation of the water 54

Later use of kerosene 55 ,

Other larvicides 57

Permanganate of potash 57

Proprietary mixtures 58

Experiments of Celli and Casagrandi 58

Tar and its compounds 60

Eucalyptus trees 62

Drainage and community work 63

Appendix ' 66

ILLUSTRATIONS.

Page.

Fig. 1. Culex pungens: Eggs and young larvae 23

2. Culex pungens: Head and mouth parts of larva 24

3. Culex pungens: Full-grown larva and pupa 26

4. Culex pungens: Adults, male and female, with structural details 27

5. Culex tseniorhynchus: Female _ 28

6. Anopheles quadrimaculatus: Adult male and female 32

7. Resting positions of Culex and Anopheles compared 33

8. Resting positions of Anopheles on vertical and horizontal walls 34

9. Resting positions of Anopheles and Culex, after Waterhouse 34

10. Anopheles quadrimaculatus: Egg mass 35

11. Anopheles quadrimaculatus: Isolated eggs from above and below 35

12. Anopheles quadrimaculatus: Newly hatched lame 36

13. Half-grown larvie of Anopheles quadrimaculatus contrasted with same

stage of Culex pungens 37

14. Feeding position of larva of Anopheles quadrimaculatus contrasted

with that of Culex pungens 38

15. Anopheles quadrimaculatus: Full-grown larva, showing head from

above and below 39

16. Anopheles quadrimaculatus: Eupa contrasted with that of Culex

pungens 40

17. Anopheles punctipennis: Head of full-grown larva from above 41

18. Anopheles punctipennis: Adult female 43

19. Anopheles crucians: Adult female 44

20. Psorophora ciliata: Adult female 45

21. Megarhinus rutilus: Adult female 46

22. Aedes sapphirinus: Adult female 47

NOTES ON THE MOSQUITOES OF THE UNITED

STATES.

ON MOSQUITOES IN GENERAL.

Abundance of mosquitoes. — The literature of popular entomology is
full of instances of the enormous numbers in which mosquitoes occa-
sionally occur. Persons interested in this line of curious reading
should consult Kirby and Spence’s An Introduction to Entomology,
Volume 1, pages 112-120, and Frank Cowan’s Curious Facts in the
History of Insects, pages 278-286. Referring to their occurrence in
the far northern regions, Kirby and Spence, for example, say: “In Lap-
land their numbers are so prodigious as to be compared to a flight of
snow when the flakes fall thickest or to the dust of the earth. The
natives can not take a mouthful of food or lie down to sleep in their
cabins unless they be fumigated almost to suffocation. In the air you
can not draw your breath without having your mouth and nostrils
tilled with them, and unguents of tar, fish grease, or cream, or nets
steeped in fetid birch oil are scarcely sufficient to protect even the case-
hardened cuticle of the Laplander from their bite.” Elsewhere the
same authorities say: “In the neighborhood of the Crimea the Russian
soldiers are obliged to sleep in sacks to defend themselves from the
mosquitoes, and even this is not a sufficient security, for several of
them die in consequence of mortification produced by the bites of these
furious bloodsuckers.” Elsewhere: “And Captain Stedman, in Amer-
ica, as a proof of the dreadful state to which he and his soldiers were
reduced by them, mentions that they were forced to sleep with their
heads thrust into holes made in the earth with their bayonets and
their necks wrapped round with their hammocks.” Humboldt says:
“Between the little harbor of Iliguerote and the mouth of the Rio
Unare the wretched inhabitants are accustomed to stretch themselves
on the ground and pass the nights buried in the sand 3 or 4 inches
deej), leaving out the head only, which they cover with a handker-
chief.” Theodorctus says that Sapor, King of Persia, was compelled
to raise the siege of Nisibis by a plague of gnats, which attacked his
elephants and beasts of burden and so caused the rout of his army.

In modern times nearly every hunter and fisherman in this country
has had experience with mosquitoes which renders easy of belief all
of the old-time stories. The instance mentioned in Bulletin No. 4, of

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the observations by Mr. Schwarz, of this office, at Corpus Christi,
Tex., could be practically duplicated by many persons. He showed
that when the wind blows from any other direction than south “ hun-
dreds of thousands of millions” of mosquitoes blow in upon the town.
Great herds of hundreds of horses run before the mosquitoes in order
to got to the water. With a change of wind, however, the mosquitoes
blow away. Many regions, especially along the seacoast, have been
actually rendered uninhabitable by the abundance of mosquitoes, and
they have been a serious drawback to the settlement of many other-
wise advantageous and fertile localities.

Dr. Otto Lugger reports, on pages 216,217 of his annual report for
1896 as entomologist to the Minnesota State Agricultural Experiment
Station, an interesting series of observations to determine the number
of mosquitoes which may be bred in an ordinary rain barrel. The
observations were made at St. Anthony Park, Minnesota. On July 6,
1896, the water in one barrel was filtered and was found to contain
17,259 eggs, larvae, and pupae. On July 22, 1896, by a similar proc-
ess, 19,110 mosquitoes were counted. When we consider that at
least twelve generations may breed in a summer it is obvious, from
Dr. Lugger’s account, that a neighborhood may be well supplied
from one neglected rain-water barrel.

Alaskan and other fa/r northern mosquitoes. — Since the opening up
of the gold fields in Alaska and the great influx of miners and traders,
knowledge of the abundance and ferocity of the Alaskan mosquitoes
has become widespread, and surveying parties from the United States
Coast and Geodetic Survey and the United States Geological Survey
in starting for Alaska for their summer’s work are in the habit of con-
sulting this office for the best remedies for mosquito bites. Those
who were in Alaska the preceding year always state that they never
experienced or even imagined anything in the mosquito line quite equal
to those found in our northern territory. Mr. W. C. Henderson, of
Philadelphia, who spent some time in Alaska recently, writes : “They
existed in countless millions, driving us to the verge of suicide or
insanity.” Nothing has as yet been published regarding the exact
species found in Alaska, but Mr. Coquillett has determined Culex con-
sobrinus and Culex impiger from specimens collected by Prof. Trevor
Kincaid on the Harriman expedition of 1899. C. consobrinus was
collected at Sitka June 16, and Yakutat June 21; and C. invpigei' was
taken at Sitka June 16, Yakutat June 21, Virgins Bay June 26, and
Popoff Island July 8-16.

That the knowledge of the existence of mosquitoes in boreal regions
is not new is shown by the quotation just made from Kirby and Spence,
and in Bulletin No. 1 the writer mentioned some of the instances of
record by arctic explorers, citing, for example, the narrative of C. F.
Hall’s second arctic expedition, in which the statement is made that

11

mosquitoes appeared on the 7th of July, 1869, in extraordinary
abundance, and of Dr. E. Sterling, of Cleveland, Ohio, who sent us an
account of the appearance of mosquitoes by thousands in March, 1844,
when he was on a snowshoe trip from Mackinaw to Sault Ste. Marie.
Their extraordinary appearance at that season of the year was remark-
able as indicating a most plentiful hibernation. Mr. H. Stewart, of
North Carolina, was also quoted as noticing, on the north shore of
Lake Superior, in 1866, in the warm days of March, when the snow was
several feet deep and the ice on the lake 5 feet in thickness, that mos-
quitoes appeared in swarms, “literally blackening the banks of snow
in the sheltered places.” Dr. Otto Lugger was also quoted as stating
that Oidex eonsobrinvm made its appearance in April, 1896, at St.
Anthony Park, Minnesota, in a genuine swarm with a heavy snow-
storm, at a time when all the lakes were covered with ice.

Dr. Lugger has also called the writer’s attention to the fact that Dr.
Emile Bessels, of the Polaris expedition, was obliged to interrupt his
work in Davis Straits (latitude 72° N.) on account of the multitude of
these insects.

Length of life of the adult mosquito. — A curious and as yet unex-
plained point in regard to a phase of mosquito existence is their extra-
ordinary abundance at certain times upon dry prairies miles from water,
which has led to the very generally accepted idea among far Western-
ers that all mosquitoes do not need pools of stagnant water in which to
breed, but that certain of them mast have some other breeding habit.
This supposition still appears incredible to the writer, who is much
more inclined to attribute this abundance in dry regions to a greater
longevity on the part of the adult mosquitoes of certain species than
has been proven, thus enabling these great swarms to live from one
rainy spell to another, no matter how widely separated. The gravid
females of most insects seem to be able to live until they have oppor-
tunity for appropriate oviposition. The writer is frequently asked as
to the duration of the adult stage of mosquitoes, but beyond the
statement that although adults hibernate, living in this condition from
November until April or May in the latitude of Washington, he is
obliged to state that they die rather quickly in confinement in the
summer. He has had living specimens of Anopheles quadnmacidatus
confined in breeding jars for eight days, all dying, however, at the
expiration of that time. Dr. Woldert has kept adults for fifteen days
in a wide-mouthed bottle in which was placed a small slice of banana,
the gauze with which the bottle was covered being sprinkled every
day. Other specimens were kept from fifty to sixty days, but this
was in the late fall, and many of them would probably have hiber-
nated. Dr. Manson states that they may be kept for weeks in a glass
vessel containing a piece of ripe banana, the banana being renewed
every three or four days.

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Life history of mosquitoes in general— In general terms the biology
of the CulicidfB — the family to which the true mosquitoes belong—
may briefly be summed up. All general statements heretofore have
been based upon the life history of one or two species of the genus
Culex, yet it is certain that such remarks will not only not hold for
the whole family, but that, except in a general wa}r, they will not hold
for all the species of Culex. So far as is definitely known, the larvae
of all mosquitoes are aquatic, although they are true air breathers;
that is to say, they must come to the surface of the water to breathe.
They are rapid breeders and pass the pupal condition also in water,
but floating normally at the surface. They pass through several gen-
erations in the course of a year and hibernate as adults. Hibernating
mosquitoes may frequently be found during the winter months in
barns and in the cellars and cold garrets of houses. Dr. W. S.
Thayer, of Baltimore, informs the writer that he found Anopheles
crucians and A. quadrimaculatus hibernating in enormous numbers in
barns near New Orleans, clustering under the roofs and on the walls.
In the extreme Southern States many mosquitoes are active all through
the winter, and mosquito bars are almost as necessary at Christmas
time as during the summer.

Food of adult mosquitoes. — It is a well-known fact that the adult *
male mosquito does not necessarily take nourishment and that the
adult female does not necessarily rely on the blood of warm-blooded
animals. The mouth parts of the male are so different from those of
the female that it is probable that if it feeds at all it obtains its
food in a quite different manner from the female. They are often
observed sipping at drops of water, and in one instance a fondness
for molasses has been recorded.

The writer has already placed on record the instance in which his
colleague, Mr. E. A. Schwarz, observed a male mosquito sipping beer,
but the most interesting instance of alcoholism of the male mosquito
which has come to his notice was described in a letter received last
spring from Dr. St. George Gray, of Castries, St. Lucia, British
West Indies. Dr. Gray wrote:

“The males, especially C. pipiens, are very fond of wine, and almost every day I
can catch one or two — always males — on the neck of the decanter or in a wineglass
that has just been used. I put a few mosquitoes under a hell jar one day in order to
watch them. I put a single drop of port wine under the jar, as I had heard that
mosquitoes could be kept alive for a long time on wine. When I went to look at
them a few hours later I found them all apparently dead, so I put them in a dry
bottle, intending to pin them later. When I went to pin them shortly afterwards
they were all staggering about in the most ridiculous manner — they were drunk!”

The female mosquitoes are normally without much doubt plant
feeders. Why they should draw blood at all is a question which has
not been solved. It has been surmised that a supply of highly nutri-

13

tive fluid is necessary for the formation of the eggs, but this supposi-
tion is at once emphatically negatived by the fact that mosquitoes
abound in regions into which warm-blooded animals never penetrate.
The statement which the writer has elsewhere made, that not one in a
million ever gets the opportunity to taste the blood of a warm-blooded
animal, is unquestionably an underestimate. There are in this country
enormous tracts of marshy land into which warm-blooded animals
never find their way and in which mosquitoes are breeding in count-
less numbers, and when we get within the Arctic Circle and other
uninhabited regions the point is emphasized. Scattered through the
seven volumes of Insect Life arc records of the observation of the
vegetarian habit, one writer stating that he has seen mosquitoes with
their beaks inserted in boiled potatoes and another that he has seen
watermelon rinds with many mosquitoes settled upon them busily
engaged in sucking the juice. That they may and occasionally do
feed upon other than warm-blooded animals, however, is evidenced
by an observation by the late Dr. H. A. Hagen, who mentions taking
a species of mosquito in the Northwest which was engaged in feeding
upon the chrysalis of a butterfly, while there are several instances on
record where they have been observed puncturing the heads of young
* fish and killing them.

ll<rw far will mosquitoes fly? — The question is often asked: “How
far will mosquitoes fly from their breeding places, or how far can they
be driven by the wind?” In some instances this becomes a matter of
practical importance, since, if mosquitoes fly great distances, extermi-
nativc work on the breeding places near a house or community will be
of comparatively slight avail. There exists on this point a difference
of opinion. In a discussion at the meeting of the Association of Eco-
nomic Entomologists at Boston, in August, 1898, Dr. John B. Smith
stated, in referring to the possibility of mosquitoes being carried by
strong winds to considerable distances, that ho had noticed that they
would not rise or take flight when a brisk breeze was blowing, and
that even a comparatively slight breeze will keep them from upper
stories in houses. He, therefore, doubted the wide distribution of
mosquitoes by high winds. Dr. H. T. Fernald stated that at Cold
Spring Harbor, Long Island, with a north breeze there arc no mos-
quitoes. With a south breeze, on the other hand, they are often very
troublesome, especially after a prolonged gentle wind of live or more
hours’ duration. There are no pools in the center of the island, and
the mosquitoes are supposed to have been carried from the south shore,
a distance of some 15 miles. This question became a very practical
one to the members of the Richmond County Country Club on Staten
Island, in their operations against the breeding places of mosquitoes
on the island, since, if a new supply could be carried over by the
winds from the New Jersey coast near by, a largo portion of their

14

labor would be wasted. Mr. W. C. Kerr, the originator of the mos-
quito work at that place, and an excellent observer, is decidedly of
the opinion that mosquitoes are not brought over from New Jersey.

Almost everyone must have noticed the habit of mosquitoes of
clinging to branches of trees and grasses during a high wind, swarm-
ing out in flight as the wind subsides, but there must be instances
when they are greatly aided in spreading by such gentle winds as
those mentioned above by Dr. Fernald.

In this connection an observation made by Mr. R. M. Reese in
Baltimore is significant. He found that by treating the privy vault
in his backyard with kerosene, the supply of mosquitoes to the house
was greatly reduced, although there were many other breeding places
only a little farther removed.

Another significant instance was mentioned by Prof. Herbert
Osborn at the Boston meeting of the Association of Economic Ento-
mologists. He said that in dry seasons the small pools within a quar-
ter to a half a mile from the college buildings at Ames, Iowa, dry up
and the mosquitoes disappear, in spite of the fact that within about a
mile there are large pools which never become dry.

On this point Mrs. C. B. Aaron writes very sensibly as' follows
(Dragon Elies vs. Mosquitoes — The Lamborn Essays, Appleton & Co.,
1890, pp. 35-36):

The migration of mosquitoes has been the source of much misapprehension on the
part of the public. The idea prevalent at our seaside resorts that a land breeze brings
the swarms of mosquitoes from far inland is based on the supposition that it is capable
of long-sustained flight and a certain amount of battling against the wind. This is an
error. Mosquitoes are frail of wing ; a light puff of breath will illustrate this by hurling
the helpless creature away, and it will not venture on the wing again for some time after
finding a safe harbor. The prevalence of mosquitoes during a land breeze is easily
explained. It is usually only during the lulls in the wind at such times that Culex can
fly. Generally on our coast a sea breeze means a stiff breeze, and during these even the
Odonata, and often the robust and ventursome Tabanidas, will be found hovering on
the leeward side of the houses, sand dunes, and thick foliage. In the meadows south
of Atlantic City, N. J., large swarms of Culex are sheltered in the dense grass or
wind-battered tree tops on the off side of the sand dunes. Here, in common with all
localities so exposed to searching wind, the trees and large bushes are much stunted
in growth and battered down to a flat top and common level by the wind. In these
matted branches, dense with the close-clustered foliage, the mosquitoes may be dis-
covered in such numbers as to bring despair to the heart of the student who is plot-
ting their final extermination. While the strong breezes last Culex will stick close
to these friendly shelters, though a cluster of houses may be but a few rods off, filled
with unsuspecting mortals who imagine their tormentors are far inland over the stilt
meadows. But if the wind dies down, as it usually does when veering, out come
swarms upon swarms of the females intent upon satisfying their depraved taste for
blood. This explains why they appear on the field of action almost immediately
after the cessation in the strong breeze; on the supposition that they were blown far
inland, this sudden reappearance would be unaccountable.

Carriage of mosquitoes by railway trains. — The State of New Jersey
has an unfortunate reputation in connection with mosquitoes. While

15

it is undoubtedly true that mosquitoes are very abundant inmost parts
of the State, that fact does not mean to the writer that in the greater
part of the State there are any more breeding spaces or that mosqui-
toes are any more prolific within the State borders than elsewhere.
It does, however, seem to him that there is constant carriage inland
from the marshy seacoast of very many mosquitoes, but by this he
does not intend to convey the idea that they are carried by wind or
that they fly to any great distance inland. There are other means of
conveyance, and of these railway trains seem to be very important.
All through the summer evenings many trains are started inland from
Weehawken, Hoboken, Jersey City, South Amboy, Long Branch,
Atlantic City, Ocean City, and Cape May, N. J. Many of the cars, as
the writer knows from experience, contain mosquitoes by the hun-
dreds. In this way unlimited quantities of mosquitoes are carried
unlimited distances, and, emerging from the cars, will start to breed
even in localities where mosquitoes are ordinarily rare, or would be
rare under ordinary conditions. In this way even mountain resorts
will get their supply of lowland mosquitoes, and with the improve-
ment of railway service and the increase in number of through cars
the danger is constantly increasing. The writer knows of one instance
in the Catskill Mountains in New York where the infestation of a pre-
viously uninfested place could have been brought about in no other
way. Through parlor and through baggage cars now run from Jersey
City and Weehawken into the heart of the Catskills and through trains
from Boston into the White Mountains.

In the same way through cars run from Baltimore into the Blue
Ridge, and thus a constant source of supply may be, and undoubtedly
is, kept up.

Sow long can the lai'vce live out of water? — At the meeting of the
Association of Economic Entomologists above referred to, Dr. Smith
asked if it were possible for mosquitoes to breed in mud, and sug-
gested that there was no reason to believe that the actual presence of
water was necessary for all mosquito species. The writer has seen a
statement from some Californian, which he is unable to place at the
present time, to the effect, that there is a prevalent belief in some parts
of the United States that when a surface pool dries up half-grown
larva? may exist in the drying mud for some time, reviving with a
fresh rain. Mr. C. A. Sperry, of Chicago, wrote us early in 1899
and advanced the same theory. He said that experiments made in
small vessels had always been very unsatisfactory to him, and that he
abandoned that method and sought the natural breeding places for
investigation and experiment. Early in July he found a wet-weather
pond with mosquito larva? in it, the pond being nearly dry. In a few
days the water was all gone. He examined closely and discovered no
dead larvae. In about a week it rained, and as soon as the rain

16

stopped he went to the place and found the mosquito larva? all through
the water as lively as ever, and they began to issue as adults about a
week from that time. Again lie discovered a place where the water
had nearly dried up, and hundreds of mosquito larva? were seen by
him on the wet ground. Three days later it rained, and he found the
larvae in the water as lively as ever. In the same way Mr. Benjamin
S. Paschall, of Newfield, N. J., has communicated to us observations
of his own which indicate to him a possibility that mosquitoes may
breed in grass or moist earth.

Experiments made at this office on a small scale in glass vessels
have shown that the larva? of Culex will exist for some little time in
wet mud, and some of them will successfully transform after water
has been added. In no case, however, were we able to revive larvae
in mud from which the water had been drawn off for more than forty-
eight hours, and after twenty-four hours only a small proportion of
the larvae revived. An interesting pool has been under observation
during the present month. The pool contained a surface area of about
21 square feet, and was fed entirely by rain water and surface drain-
age, reaching a depth when full of about 1 foot. All through the sum-
mer this pool is well stocked with mosquito larva?. After a somewhat
long drought the water was observed on July 18 to have evaporated
almost entirely, a small puddle in the center of the cavity, containing
only 3 or 1 cubic inches of water, remaining. It was dark in color,
owing to the drainage from a manure pile near by; and to the casual
observer showed no signs of life. The water in this little puddle was
very shallow. On dipping in a coffee strainer, however, it was found
to be literally massed with nearly full-grown mosquito larvae, many
hundreds of which had been brought together into this restricted
place. The drying continued until there was almost no water left.
On the night of the 20th came a heavy rain, followed with a still
heavier one on the morning of the 22d. On the 23d the pool was
found to be entirely full of water and to contain its usual stock of
mosquito larvae.

This may be safely said to indicate the usual habit of mosquito
larva? in evaporating pools. As the water gradually recedes toward
the deepest portion of the excavation, the larva? recede with it, con-
centrating themselves at the deepest point, i. e., at the point where
the moisture remains longest. Knowing as we do, then, that even
in the absence of any free water the larva? will remain alive in moist
mud for from twenty-four to forty-eight hours, it is evident that
such a pool as the one described gradually drying would give the
appearance of having been practically dried up for some days before
the last cubic inch of free water has entirely disappeared. The con-
centration of many larva? at this point in the manner which has been
described could not fail to give rise to the belief that mosquito larva?

17

will exist in the absence of free water for a much longer period than
is really the case. In the opinion of the writer, where the mud dries
up entirely the mosquito larva? are necessarily killed, but that they
may exist in very wet mud for a longer or shorter time is true.

An interesting observation bearing upon this point has been made
by Dr. St. George Gray, of Castries, St. Lucia, British West Indies,
and reported in the Journal of Tropical Medicine, London, May 15,
1900. He says that on February 7, 1900, he examined a spot where he
had obtained larvae of Anopheles a few months before. The pool had
been dry for three weeks, hardly any rain having fallen during that
time. The surface of the mud at the bottom was cracked and dry,
although soft enough under the crust. He put the mud into a clean
pickle bottle and put about 3 inches of filtered water over it, but there
was no result. He also took some grass from the sides of the pool and
put that grass into another pickle bottle, adding 3 inches of filtered
water. On the following morning ho found a few minute larvae
wriggling about in this bottle. These rapidly grow in size, and he
soon had a half dozen healthy looking larvae in his bottle. On the 21st,
a fortnight after he had taken the grass from the sides of the pool, ho
reared the imago of Gulex tc&niatm. F rom this observation he argues
that some species of Culcx, at any rate, do not always lay their eggs
on the surface of the water, but where they will bo washed into the
pool b}r the first heavy rain. Other similar experiments were failures.
This record is a very interesting one, but, like all isolated observations,
needs verification.1 It may here be mentioned that Drs. J. W. W.
Stephens and S. 11. Christophers, in their article on “The distribution
of Anopheles in Sierra Leone,” published in the reports of the malarial
committee to the Royal Society (London, July 6, 1900), stated that
they were unable to hatch the eggs of Anopheles after desiccation on
blotting paper for more than forty -eight hours, although they hatched
after twenty-four and forty -eight hours’ drying, respectively.

The number of species of mosquitoes. — As regards the different kinds
of mosquitoes, about 250 species arc known, of which only about 30
have been found in the United States. These are divided into 5 differ-
ent genera, each of which will receive consideration in the following
pages. Of the malarial genus Anopheles, Mr. F. V. Theobald writes
us there are 27 species in the British Museum collection.

MOSQUITOES AND MALARIA.

'This is not the place to discuss at length the history of the discover-
ies which have brought about the very perfect proof that mosquitoes
may and do transfer the malaria germ from a malaria patient and

lDr. Walter Reed, U. S. A., tells me that Dr. Lazear has just made a similar
observation in Cuba.

3949 2

18

deposit it in the blood ot a healthy person. Those interested are
referred to the admirable paper entitled “On the role of insects,
Arachnids and Myriapods, as carriers in the spread of bacterial and
parasitic diseases of man and animals; a critical arid historical study,”
by George TI. Nut tall, M. D., Ph. D., published in Volume VIII of
the Johns Hopkins Hospital Reports, and to later American summaries,
among which may be mentioned that by Dr. W. N. Berkeley in the
New York Medical Record for December 23, 1899, by Dr. Albert
Woldert in the Journal of the American Medical Association for Feb-
ruary 10, 1900, 1 and by Dr. William Britt Burns in the Memphis Medi-
cal Monthly for March, 1900. One of the most thorough of the recent
reviews will be found in Nature for March 29, 1900, pages 522-527,
entitled “Malaria and mosquitoes,” a lecture delivered at the Royal
Institution of Great Britain on March 2, by Maj. Ronald Ross, D. P. H.,
M. R. C. S., lecturer in tropical medicine, University College, Liver-
pool, himself one of the workers whose results contributed most
materially to the establishment of definite proof. Another recent
account will be found in the Popular Science Monthly for July, 1900,
by Dr. Patrick Manson, entitled “Malaria and the malarial parasite.”
It should be stated here, however, that only the mosquitoes of the
genus Anopheles have been found to contain the human blood para-
sites, although it does not appear from the published accounts which
have met the writer’s eye that any other genera than Anopheles and
Culex have been studied in this connection.

The Italian observers have found that all three species of the human
Hsemamoebidse are cultivable in Anopheles claviger and not only in
this but in other Italian species of Anopheles, while they, together
with Ross and other observers, have failed to cultivate the parasites
in Culex. The same fact is upheld by the extended observations made
in West Africa and in this country so far as observations have been
made as yet. The writer, however, wishes to emphasize the point
which he made before the American Medical Association on June 6,
1900, that American physicians, especially those in the Southern States,
should not delay the investigation of the very large mosquitoes of the
genus Psorophora and Megarhinus f.'om the malarial standpoint. Both
of these genera have been figured and described in succeeding pages.

SYNOPTIC TABLES OF THE NORTH AMERICAN MOSQUITOES.

In order to enable the ready determination of our different mos-
quitoes the writer published in Circular 40, second series, of this office,
in February of the present year, a series of tables, drawn up at his
request by Mr. D. W. Coquillett, of the office force, comprising (1) a

1 Dr. Woldert’ s article contains a good account of the internal anatomy of mosqui-
toes and describes his methods of dissection.

19

synopsis of the five genera under which the long-beaked, blood-suck-
ing species known to occur in North America were divided; (2) a
synoptic consideration of the species of the genus Culex, divided into
(a) table of the recognized species, specimens of which occur in the
National Museum collection, and (b) an account of the unrecognized
species, which are known only from the literature; (3) a synoptic con-
sideration of the species of the genus Anopheles, divided into (a)
recognized forms, and (b) unrecognized forms; (4) a brief description
of the only valid known species of the genus Psorophora; (5) a synop-
tic table of the three known species of the genus Megarhinus; and (6)
a synoptic consideration of the two known species of the genus Aedes.

Mr. Coquillett’s tables are here reprinted with slight changes:

I. — Generic Synopsis.

The following table contains all the genera of the long-beaked mosquitoes known
to occur in North America. The males are readily recognized by the an ten me being
densely covered with long hairs; in the females the hairs of the an ten me are short
and very sparse:

1. Palpi in the male at least nearly as long as the proboscis; in the female less than

one-half as long 2.

Palpi in both sexes at least almost as long as the proboscis Anopheles.

Palpi in both sexes less than one half as long as the proboscis Aedes.

2. Proboscis straight or nearly so, colors of body brown and yellowish 3.

Proboscis strongly curving downward toward the tip, colors bluish or greenish.

Megarhinus.

3. Legs bearing many nearly erect scales Psorophora.

Legs destitute of such scales Culex.

II. — Genus Culex.

(«) RECOGNIZED SPECIES.

Males.

1.

2.

3.

4.

5.

Front tarsal claws bearing a distinct tooth near the middle of the underside of
each 3.

Front tarsal claws bearing two teeth on the underside of one claw, and one on
underside of the other, proboscis destitute of a whitish band near the mid-
dle 2.

Front tarsal claws with one tooth on underside of one of the claws, none on the
other, bases of tarsal joints white, proboscis destitute of a whitish band near

the middle fascialus Fabr.

Tarsi distinctly white at bases of the joints exciians Walk.

Tarsi not white at bases of the joints consobrinus Desv.

Proboscis destitute of a whitish ring near the middle 4.

Proboscis with such a ring, ends of tarsal joints white tarsalis Coq.

Bases of tarsal joints not white 5.

Bases of tarsal joints white stimulans Walk.

Petiole of submarginal cell less than one-third of the length of that cell.

pungens Wied.

Petiole of submarginal cell at least one-half of the length of that cell.

impiger Walk.

Females.

1. Front tarsal claws bearing a distinct tooth near middle of underside of each.. 2.
Front tarsal claws destitute of teeth 7.

20

2. Proboscis destitute of a white ring near the middle 3.

Proboscis marked with such a ring, bases of tarsal joints white.

txniorhynchus Wied.

3. Bases of tarsal joints distinctly white 4.

Bases of tarsal joints never white 5.

4. Mesonotum marked with four stripes of silvery scales fasciatus Fabr.

Mesonotum destitute of such stripes:

Fifth joint of hind tarsi white tscniatm Wied.

Fifth joint, except its extreme base, dark brown slimuluns Walk.

5. Last two joints of hind tarsi never white 6.

Last two joints of hind tarsi snow white posticalus Wied.

6. Abdomen marked with a cross band of whitish scales at base of each segment.

impiger Walk.

Abdomen never marked in this manner, but with a cluster of whitish scales at
front angles of some of the segments triserialm Say.

7. Proboscis marked with a distinct whitish ring near the middle, tarsi white at

sutures of the joints 8.

Proboscis destitute of a whitish ring near the middle 9.

8. Tarsal joints white at bases only perturbans Walk.1

Tarsal joints white at both end's tarsalis Ooq.

9. Tarsi white at bases of joints 10.

Tarsi never white at bases of the joints 12.

10. Mesonotum never marked with stripes of silvery scales 11.

Mesonotum marked with four stripes of silvery scales, first tarsal joint never

marked with a whitish ring near the middle : signifer Coq.

11. First tarsal joint marked with a whitish ring near middle of each.

excrucians Walk.

First tarsal joint destitute of such a ring excitans Walk.

12. Petiole of submarginal cell less than one-third of the length of that cell.

pungens Wied.

Petiole of submarginal cell at least almost one-half of the length of that cell.

consobrinus Desv.

(6) UNRECOGNIZED SPECIES.

annulatus Schrank. This European species was credited to our fauna by Osten
Sacken. The description agrees fairly well with specimens which I have identified
as excitans, Walker, except that in the latter there is no white ring on the femora
toward their apices.

boscii Desv. Probably a rubbed specimen of pungens.

nigripes Zett. Black, the legs of the male dark yellow, hairs of pleura of female
gray, a band of white scales at base of each segment of her abdomen.

rubidus Desv. The description was apparently foimded on a rubbed specimen of
Psorophora ciliata.

lestaems v. d. Wulp. Is probably a somewhat injured example of consobrinus.

incidens Thomson. Is evidently a synonym of impiger Walker.

bigoti Bellardi. According to the figure and description, the bands of black scales
are at the bases of the abdominal segments; in the recognized species these bands are
always at the apices of the segments. In other respects this species must greatly
resemble pungens.

cubens'is Bigot. Apparently founded on a badly rubbed specimen of pungens.

frater Desv. This name was proposed for the Culex fasciatus of Wiedemann, under
the impression that this is not the same species as the one described by Fabricius
under the same name. It seems quite certain, however, that the word “proboscis
in Fabricius’ description was simply a lapsus for “palpi,” and with this emendation
the two descriptions agree very well.

mexicana Bellardi. Is evidently a synonym of posticalus. .

provocans Walker. Is probably a synonym of stimulans. In some specimens ot
this species the light color at the bases of the tarsal joints is very indistinct.

terrilans Walker. Is apparently a synonym of pungens.

’Mr. F. V. Theobald, after studying Walker’s type of perturbans, writes us that it
has toothed claws in the female.

21

Our recognized species of Culex and their synonyms may be listed as follows, the
synonyms indented:

consobrinus Desv.

? annulimanus v. d. Wulp (Ano-
pheles).

impatien s Walker.
inornatus Williston.
pinguis Walker.
punctor Kirby.

? testaceus v. d. Wulp.
excitant Walker.

? annulatus Osten Sacken (nec
Meigen, etc.).
excnicians Walker.
fasciatus Fabr.
f rater Desv.
mosquito Desv.
laeniaius Wied.
impiger Walker.

implacabilis Walker.
incident Thomson.

? quinquefusciatm Say.

III. — Genus Anopheles.

(a) RECOGNIZED SPECIES.

1. With a yellowish white spot near three-fourths of the length of the front margin
of the wing; scales of last vein white, those at each end black . punclipmnis Say.

Without such a spot 2.

2. Scales of last vein wholly black, palpi wholly black quadrimaculatm Say.

Scales of last vein white, marked with three black spots, palpi marked with white
at bases of last four joints crucians Wied.

(b) UNRECOGNIZED SPECIES.

perturbans Walker.
poslicaius Wied.

? mexicanus Bellardi.
musicus Say.
jmngens Wied.

? boscii Desv.

? cubensis Bigot.

? territans Walker.
signifer Coquillett.
stimulant Walker.

? provocans Walker.
taeniorhynchus Wied.
damnosus Say.
sollicitans Walker.
tarsalis Coquillett.
Iristriatus Say.

The following species which have been credited to our country have not been
recognized with certainty; some of them probably do not belong to the present
genus, while a few were evidently founded on badly rubbed specimens in which the
distinctive characters were therefore wanting:

annvliman m v. d. Wulp. I strongly suspect that this does not belong to the present
genus; the description applies fairly well to the male of Culex comobnnus Desv.

ferruginosus Wied. This author proposes this name for the species previously
described by Say under the name of Culex quinquefasciatus, but the description which
he gives differs so decidedly from the one published by Say as to give the impression
that it is founded on a different species. I strongly suspect that the type of ferru-
ginosus is a rubbed example of Anopheles crucians, which was described from the same
locality. Say’s description of his Culex quinquefasciatus agrees very well with the
species which I have identified as Culex impujer Walker.

maculipennis Meigen. I strongly suspect that this European form is identical with
our Anopheles quadrimaculatm Say, but this point can not be settled definitely at
present, owing to the lack of any European specimens for comparison with ours.

nigripes Staeger. This European species should be readily recognized by its
unspotted wings.

albimanus Wied. Differs from our other species by the snow-white apices of the
tarsi.

Anopheles pictus Loew is evidently a synonym of A. crucians Wied.

Our recognized species of Anopheles and their synonyms may therefore be listed
as follows, the synonyms indented:

crucians Wied.
pictus Loew.

V ferruginosus Wied.

punclipennis Say.

hiemcdis Fitch.
quadrimacidatm Say.

? maculipennis Meigen.

22

IV. — Genus Psorophora.

Our single species is of a yellowish color, usually varied with brown, the bases of
the tarsal joints white. It is considerably larger than any of our other species of
yellowish or brown mosquitoes:

tiliatus Fabr.
conterrens Walker.
molestus Wied.

? rubidus Desv.

V. — Genus Megarhinus.

Our three species are among the largest in this family, and are not known to occur
north of the District of Columbia. They may be separated as follows:

All tarsi marked with white rutilus Coq.

Hind tarsi alone marked with white povtoTicensis Foeder.

None of the tarsi marked with white hxm orrho idu lis Fabr.

VI. — Genus Aedes.

Our two species are among the smallest of our mosquitoes, and have a pale
brownish ground color. They may be distinguished as follows:

Thorax marked with a median violet blue stripe sapphirinus 0. S.

Thorax destitute of such a stripe fmcm 0. S.

THE BIOLOGY OF CULEX, WITH REMARKS UPON SOME OF THE SPECIES.

It is tolerably certain that the life round of all of the species of the
genus Culex is practically the same. They will differ more or less in
the character of the water in which they preferably breed, and differ-
ing in this respect, they will differ also in some degree in their pre-
ferred food, which consists of all sorts of aquatic micro-organisms.
Down to the time when the writer published his account of Oulex
pungens, in Bulletin No. 4, New Series, of this office, there was not
in any published work a thoroughly satisfactory figure of a well-
determined species of mosquito from the United States, or of its
earlier stages. The statements quoted in the text-books and manuals
dated back in general to the time of Reaumur — more than one hun-
dred and fifty years ago. Reaumur’s observations were made in the
month of May upon a species {Oulex pipiens) which does not occur in
North America, and the observations were all made at Paris, so that
statements as to the duration of the insect in any stage would be
incorrect even for the same species in a warmer or colder locality.
The following account of the life history of Culex pungens (fig. 1) is
quoted from the writer’s bulletin above cited:

Life history of Culex pungens. — The operation of egg laying was
not observed, but it probably takes place in the very earl}' morning
hours. The eggs are laid in the usual boat-shaped mass, just as those
of Culex gripiens, as described by Reaumur. We say boat-shaped mass,
because that is the ordinary expression. As a matter of fact, however,
the egg masses are of all sorts of shapes. The most common one is

the pointed ellipse, convex below and concave above, all the eggs per-
pendicular, in 6 to 13 longitudinal rows, with from 3 or 4 to 40 eggs in
a row. The number of eggs in each batch varies from 200 to 400. As
.seen from above the egg mass is gray brown; from below, silvery
white, the latter appearance being due to the air film. It seems
impossible to wet these egg masses. They may be pushed under
water, but bob up apparently as dry as ever. The egg mass separates
rather regularly, and the eggs are not stuck together very firmly.
After the}' have hatched the mass will disintegrate in a few days, even
in perfectly still water.

The individual eggs are 0.7 mm. in length and 0.16 mm. in diameter
at the base. They are slender, broader and blunt at bottom, slenderer
and somewhat pointed at tip. The tip is always dark grayish brown in

(original) .

color, while the rest of the egg is dirty white. Repeated observations
show that the eggs hatch, under advantageous conditions, certainly
as soon as sixteen hours. Water buckets containing no egg masses,
placed out at night, were found to contain egg masses at 8 o’clock in
the morning, which, as above stated, were probably laid in the early
morning, before daylight. These eggs, the third week in May, began
to hatch cpiite regularly at 2 o’clock in the afternoon of the same day
on warm days. In cooler weather they sometimes remained unhatched
until the second day. If we apply the evidence of European observers
to this species, the period of the egg state may be under twelve hours;
but there is a possibility that they arc laid earlier in the night, which
accounts for the fact that sixteen hours is the shortest period which wo
can definitely mention.

24

The larvae issue from the underside of the egg masses, and are
extiemely active at birth. When first observed it is easy to fall into
an error regarding the length of time which they can remain under
water, or rather without coming to the surface to breathe, since, in
striving to come to the surface for air, many of them will strike the
underside of the egg mass and remain there for many minntes. It is
altogether likely, however, that they get air at this point through the
eygs 01 through the air film by which the egg mass is surrounded, and
that they are as readily drowned by continuous immersion as are the
older ones, as will be shown later.

One of the fiist peculiarities whicii strikes one on observing these
newly-hatched larvae under the lens is that the tufts of filaments which
are conspicuous at the mouth are in absolutely constant vibration. This
peculiarity, and the wriggling of the larvae through the water, and

Fig. 2. — C’ulcx pungens: Head of larva from below at left; same from above at right — greatly enlarged

(original).

their great activity, render them interesting objects of study. In gen-
eral the larvae, passing through apparently three different stages, reach
maturity and transform to pupae in a minimum of seven days. When
nearly full grown, their movements were studied with more care, as
they were easier to observe than when newly hatched. At this time
the larva remains near the surface of the water, with its respiratory
siphon at the exact surface and its mouth filaments in constant vibra-
tion, directing food into the mouth cavity. Occasionally the larva
descends to the bottom, but, though repeatedly timed, a healthy indi-
vidual was never seen to remain voluntarily below the surface more
than a minute. In ascending it comes up with an effort, with a series
of jerks and wrigglings with its tail. It descends without effort, but
ascends with difficulty; in other words, its specific gravity seems to be
greater than that of the water. As soon, however, as the respiratory

25

siphon reaches the surface, fresh air flows into its tracheae, and the phys-
ical properties of the so-called surface film of the water assist it in
maintaining its position.

The respiratory tube takes its origin from the tip of the eighth ab-
dominal segment, and the very large tracheae can be seen extending to
its extremity, where they have a double orifice. The ninth segment of
the abdomen is armed at the tip with four flaps and six hairs, as shown
in fig. 3. These flaps are gill-like in appearance, though they are prob-
ably simply loeomotory in function. With so remarkably developed an
apparatus for direct air breathing there is no necessity for gill struct-
ures. Raschke1 and Hurst2 consider that the larva breathes both by
the anus arid by these gill flaps, as well as by the large tracheae which
open at the tip of the respiratory tube. Raschke considers that these
trachea; are so unnecessarily large that they possess a hydrostatic
function. The writer is inclined to believe that the gill flaps may be
functional as branchial structures in the young larva, but that they
largely lose this office in later life.

After seven or eight days, at a minimum, as just stated, the larva
transforms to pupa. The pupa, as has been repeatedly pointed out
with other species, differs most pronouncedly from the larva in the
great swelling of the thoracic segments. In this stage the insect is
lighter than water. It remains motionless at the surface, and when
disturbed does not sink without effort, as does the larva, but is only
able to descend by a violent muscular action. It wriggles and swims
as actively as does the larva, and soon reaches the bottom of the jar
or breeding place. As soon as it ceases to exert itself, however, it
floats gradually up to the surface of the water again. The fact, how-
ever, that the larva, after it is once below the surface of the water, sinks
rather than rises, accounts for the death of many individuals. If they
become sick or weak, or for any reason are unable to exert sufficient
muscular force to wriggle to the surface at frequent intervals, they will
actually drown, and the writer has seen many of them die in this way.
It seems almost like a contradiction in terms to speak of an aquatic
insect drowning, but this is a frequent cause of mortality among wrig-
glers. This fact also explains the efficacy of the remedial treatment
which causes the surface of the water to become covered with a film of
oil of any kind. Aside from the actual insecticide effect of the oil, the
larvae drown from not being able to reach the air. The structure of the
pupa differs in no material respect from that of corresponding stages
of European species, as so admirably figured and described by the older
writers, notably Reaumur and Swammerdam3, and needs no description

1 Raschke, Die Larve von Culex nemorosus, Berlin, 1887.

2 Hurst, the Pupal Stage of Culex, Manchester, 1890.

3 Even Bonanni, in 1691, gave very fair figures of the larva and pupa of a European
species. Micrographia Curiosa, Rome, MDCXCI, Pars. II, Tab. I.

26

in view of the care with which the figures accompanying this article
have been drawn. The air tubes no longer open at the anal end of the
body, but through two trumpet-shaped sclerites on the thorax, from
which it results that the pupa remains upright at the surface, instead
of with the head downward. There is a very apparent object in this
reversal of the position of the body, since the adult insect issues from
the thorax and needs the floating skin to support itself while its wings
are expanding.

In general, the adult insects issue from the pupae that are two days

Fig. 3. — Culcx pungens : Full-grown larva at left, pupa at right— enlarged (original).

old. This gives what is probably the minimum generation for this
species as ten days, namely, sixteen to twenty-four hours for the egg,
seven days for the larva, and two days for the pupa. The individuals
emerging on the first day were invariably males. On the second day
the great majority were males, but there were also a few females. The
preponderance of males continued to hold for three days; later the
females were in the majority. In confinement the males died quickly;
several lived for four days, but none for more than that period. The
females, however, lived for a much longer time. Some were kept alive

27

without food, in a confined space of not more than 4 inches deep by 6
across, for three weeks. But one egg mass was deposited in confine-
ment. This was deposited on the morning of June 30 by a female which
issued from the pupa June 27. No further observations were made
upon the time elapsing between the emergence of the female and the
laying of the eggs, but in no case, probably, does it exceed a few days.

The length of time which elapses for a generation, which we have
just mentioned, is almost indefinitely enlarged if the weather be cool.
As a matter of fact, a long spell of cool weather followed the issuing

Fig. i.—Culex pungent ; Female above, male below— enlarged (original).

of the adults just mentioned. Larvre were watched for twenty days,
during which time they did not reach full growth.

The extreme shortness of this June generation is significant. It
accounts for the fact that swarms of mosquitoes may develop upon
occasion in surface pools of rain water, which may dry up entirely in
the course of two weeks, or in a chance bucket of water left undis-
turbed for that length of time. Further, the shortness of this genera-
tion was, while not unexpected, not at all in accordance with any

28

published statements as to the length of life of any immature mos-
quito of any species. But these published statements, as previously
shown, were nearly all based! upon observations made in a colder
climate and in the month of May.

Remarks on other species of Culex.— m. he writer is inclined to believe
thftt Oulex toeniorlvynchus (fig. 5) is more or less specifically the sea-
coast mosquito of the Atlantic seaboard; that is to say, it is the
mosquito in this part of the country which is able to breed and prefers
to breed in the brackish swamps which arc occasionally overflowed at
high tide. It has been found by Mr. C. W. Johnson at Avalon,
Anglesea, and Atlantic City, N. J. ; by the writer at Far Rockaway,
Amergansett, and on the beach at Staten Island, New York ; by Mr!

Pig. 5. — Oulex tfeiuorliynchus: Female, showing the short palpi which
distinguish Culex from Anopheles; toothed front tarsal claw at right —
enlarged (original).

Barber at Chesapeake Beach, Md., and again by Mr. Johnson at St.
Augustine and Charlotte Harbor, Fla. Other species, like Culex pun-
gens, are seen at seaside resorts, but it is probable that these breed
back of the coast in fresh water. This difference in breeding habit is
very marked on the east coast of Staten Island. The people there
distinguish between the brown-legged mosquitoes and the ring-legged
mosquitoes, the former being C. pungens , which breeds in the hilly
ponds and swamps back of the bluffs, and the latter being C. tcenio-
rhyncus , which breeds in the brackish marshes below the bluffs. Dr.
A. D. Hopkins states (Bulletin IT, new series, Div. Entom., Dept.
Agric.) that what is probably this species apparently breeds in West

29

Virginia in pools and small streams fed from coal-mine drainage, the
water of which contains a large percentage of sulphate of iron.

Culex i/mpiger has been found by Mr. Pratt, of this office, breeding
in privy vaults in Alexandria, Va., and this species is likely to be the
one found usually in such places where the water is fouled with decom-
posing or excreted animal matter.

Culex taeniatus is said by Dr. Veazie, of New Orleans, to be the
so-called “day mosquito” of New Orleans; that is, the form which
Hies and bites in the daytime. This statement is corroborated to a
certain extent by Dr. St. George Gray, of St. Lucia, British West
Indies, who writes, under date of August 12 last:

I have made some observations on the hours at which the different species are
most industrious, and find that most mosquitoes have regular feeding times. For
instance, C. ixniatws is very vigorous and troublesome in the early afternoon ( bet ween
noon and 3 p. m). Then she usually takes a rest, and renews her attacks at 9 or
10 p. m. During the morning it can he found resting on walls and clothing, particu-
larly dark-colored clothing, and is easily caught.

Tlie. distribution of the) species of Culex in the United, States. — In

preparing Bulletin No. 4 the writer was at pains to borrow all of the
mosquitoes from the collections of such entomologists as he supposed
had saved specimens in this family and placed them in the hands of
Mr. Coquillett for study. The material received was not large, since
mosquitoes are difficult to preserve satisfactorily in a collection, and it is
an inexplicable fact that as a rule collectors do not save such extremely
common things as mosquitoes. Yet he was able from Mr. Coquillett’ s
work on the specimens received and on those already contained in the
national collection at Washington to show several interesting points.
As is the case with many other species of Diptera, most of the differ-
ent forms were found to be very widespread. The whole group has
little or no faunistic value; that is to say, different climatic conditions
and other environmental factors do not limit the range of the species
as they do with those of other groups. It was thus found that some
of the commoner forms, like C. consobrinns, C. excitans , C. perturbans,
and C. posticatus, and C. pwngens , were found almost all over the
country, from New England to Texas and even to southern California,
so that in almost any given locality in the United States one would lie
able to find all of these common species of Culex, with two or three
species of other genera and possibly two or three other species of
Culex. Since the publication of the bulletin (No. 4), other localities
of distribution have been ascertained, and the following list indicates
such actual localities as have come to our notice. Persons interested
will observe several points worth noticing in the list which follows.
Certain species seem to be rare, while others are very common, in
addition to being widespread. It seems from the list that Culex con-
sobrinus is a more northern form; that is, it comes nearer being
restricted to a boreal habitat than any of the other species. It is one

30

of the two , species which we have from Alaska. The other Alaskan
form which has been determined, namely, C. vm/piger , extends south
to Now Mexico, Georgia, and the island of Jamaica.

Culex tceniatus, according to Mr. Theobald, has a wide tropical and
subtropical distribution, occurring in West Africa, India, Soutii
Europe, and East and West Indies, but never in the north or south
cold temperate zones.

Culex consobrinus Desv.

Habitat: White Mountains, N. II.; Beverly, Mass., September 28 (Nat. Mus.);
Catskill Mountains, Greene County, N. Y., 2,500 feet (Howard); Illinois,
March 21, April 29, May 6, October 16 (Nason); St. Anthony Park, Minn.,
April, May, on snow (Lugger) ; Saskatchewan River, British America; South
Dakota (Nat. Mus.); Lincoln, Nebr., May, September (Bruner); Colorado
(Nat. Mus.); Los Angeles, Cal., February (Coquillett); Argus Mountains,
Cal., April (Nat. Mus.); Santa F6, N. Mex., July (Cockerell); New Orleans,
La., November (Thayer); Ottawa, Canada, May (Howard); Summit, N. J.
(Holmes); Trenton, Ontario, May 24 (Fletcher).

Culex excitans Walk.

Habitat: New Bedford, Mass. (Johnson); Lincoln, Nebr., May (Bruner); Santa
Fe, N. Mex., July (Cockerell); Laggan, British Columbia (Wickham).

Culex excrucians Walk. ,

Habitat: Ithaca, N. Y., July 14 (Comstock).

Culex fasciatus Fabr.

Habitat: Georgia, August (Coquillett); Natchitoches, La., October 6 (Johnson);
Isle of Pines, West Indies (Scudder); Kingston, Jamaica, July 13 (Johnson);
New Orleans, La., November (Thayer); eastern Texas (Woldert); Cuba
(Lazear).

Culex ihpiger Walk.

Habitat: White Mountains, N. IT.; Beverly, Mass., May 24, June 2 (Nat. Mus. );
Ithaca, N. Y., July 9 and 17, August28; Wihnuth, N. Y., June 10 (Comstock);
Saskatchewan River, British America (Nat. Mus. ); Minnesota (Lugger) ; Loudoun
Comity, Va., August 26 (Pratt): Tyrone, Ky., July 14 (Garman); Georgia
(Nat. Mus. ) ; Mesilla, N. Mex. (Cockerell); Isle of Pines, West Indies (Scudder);
Portland, Jamaica (Johnson); District of Columbia, September 12 (Barber);
Alexandria, Va. (Pratt); Ogdensburg, N. Y., June 3 (Ploward); Middletown,
Conn., Jvme (Davis); Ottawa, Canada, May 31 (Howard); Chats Rapids, Que-
bec, May 24 (Fletcher); Buckeye, Wash. (Nat. Mus.); Stikine River, British
Columbia (Wickham).

Culex perturbans Walk.

Habitat: Lakeland, Md., August 8 (Pratt); Virginia, August 17 (Pergande); Tick
Island, Fla., May 12 (Johnson); Texas (Nat. Mus.); Bayamon, Porto Rico
January (Busck); Districtof Columbia, September 1-5 (Barber); St. Elmo, Va.’
June, July (Pratt); Cuba (Lazear).

Culex posticatus Wied.

Habitat: Montgomery County, Pa., July 17 (Johnson); Texas (Nat. Mus.);
Loudoun County, Va., August (Pratt); Roanoke, Va., October (Thayer); Dis-
trict of Columbia, June 10 (Barber).

Culex tungens Wied.

Habitat: White Mountains, N. II.; Beverly, Mass., Sep em er 5; Cambridge,
Mass., September 16 to November 5; Boston, Mass.; Baltimore, Md., Novem-
bers (Nat. Mus. ), November 26 (Lugger); Charlton Heights, Md., December 1
(Pratt); District of Columbia, January 30, March 5, May 6 and 15, June 28,
July 11, August, October 10, 15, 25, and 31, November 4, 8, 13, 16, and 23,

31

December 23 (Pergande); Ithaca, X. Y., May 29, July 17, August 28 (Coin-
stock); Illinois (Nason); Minnesota (Lugger); Lincoln, Nebr., September 20
(Bruner); Lexington, Ky., November 10 (Garman); New Orleans, La., Decem-
ber 17 (Howard); San Antonio, Tex., May 5 (Marlatt); Georgia, August
(Coquillett) ; Portland, Jamaica, .(Johnson); Mexico City (Barrett); District
of Columbia, August 22, 28, September 1 (Barber); Jackson, Va., October
(Thayer); Woodstock, Va., June (Pratt); Newport News, Va., Octolicr
(Thayer); Stillwater, Okla., June (Bogue); Philadelphia, Pa., (Woldert); New
Orleans, La., June (Veazie); eastern Texas (Woldert); Summit, N. J., May
' (La Rue Holmes) ; Middletown, Conn., June (Davis); Cuba (Lazear).

CULEX SIGNIFER Coq.

Habitat: District of Columbia, June (Coquillett), May, August (Barber); St.
Elmo, Va., June 4 (Pratt).

CULEX STIMULANS Walk.

Habitat: White Mountains, N. II.; Beverly, Mass.-, June 2, July 9; Cambridge,
Mass., May; Jamaica Plain, Mass., August 25 (Nat. Mus.); Baltimore, Md.
(Lugger); Illinois, August 1, September 15, October 5 (Nason); Agricultural
College, Mich. (Gillette); Saskatchewan River, British America (Nat. Mus.);
Lincoln, Nebr. (Bruner); Colorado (Nat. Mus.); Ithaca, N. Y., June 13, IS, 29,
July 14, August 28; Wilmuth, N. Y., June 10 (Comstock); Georgia (Nat. Mus. ) ;
Bladensburg, Md., May 27 (Barber); St. Elmo, Va., June 5 (Pratt); District of
Columbia, September (Barber), June 10 (Miss L. Sullivan); Ottawa, Canada,
June 1 (Howard); Ogdensburg, N. Y., June 3 (Howard); Rochester, N. Y.
June (Ewers); Summit, N. J., May (La Rue Holmes); Middletown, Conn.,
June (Davis); Mesilla, N. Mex., October 26 (Cockerell); Tacna, Ariz., April 13
(Hubbard); Juarez, Mexico, May 12 (Cockerell); Summit, N. J. (Holmes).
Culex t.eniatus Wied.

Habitat: New Orleans, July (Veazie); Cuba (Lazear).

Culex t.eniorfiynchus Wied.

(Not the Culex Umiorhynchm Wied. of Arribalzaga.)

Habitat: Maine, August; Beverly, Mass., June, September 15 (Nat. Mus.);
Avalon, Anglesea, and Atlantic City, N. J., July 10 to 29 (Johnson); Far
Rocka way, Long Island, N. Y., August 30 (Howard); District of Columbia
(Pergande); Georgia (Nat. Mus.); St. Augustine and Charlotte Harbor, Fla.,
July; Portland, Jamaica (Johnson); Chesapeake Beach, Md. (Barber); Balti-
more, Md. (Thayer); Plymouth, N. C. (Thayer); Galapagos Islands, February
1—1 (Snodgrass).

Culex tarsalis Coq.

Habitat: Argus Mountains, Cal. , April ; Folsom, Cal., July 3 (Nat. Mus.).

Culex triseriatus Say.

Habitat: White Mountains, N. II. (Nat. Mus.); Delaware County, Pa., June 12
(Johnson); Washington, D. C., May 5 and June 10; Loudoun County, Va.
(Pratt); Near Baltimore, Md. (Thayer); Roanoke, Va., October (Thayer);
Middletown, Conn., June (Davis); New Jersey (Woldert).

THE BIOLOGY OF ANOPHELES, WITH GENERAL REMARKS.

So far as the writer can ascertain, no detailed illustrated account of
the early stages of any species of Anopheles had been published before
his paper in the Scientific American, above referred to.1 He con-
ceived it to be nearly as important that the malarial-bearing mosquitoes
should be readily recognized in their early stages as in their adult con-
dition. He was very fortunate in April of the present year in being

1 See appendix.

32

ablo to secure a large number of gravid females of Anopheles quadri-
maculatus Say through the abundance of this species near the home of
one of his assistants, Mr. Pratt, in Virginia, a few miles from Wash-
ing-ton. Mr. Pratt was enthusiastic and assiduous in collecting living
adults, and these were kept in confinement and their offspring reared
in large water jars during April and May, 1900. It may be mentioned
here that this species is without doubt identical with the European
Anopheles macidipemnis Meigen, a fact which Mr. Coquillett has always
strongly suspected, although he had no European material with which
to compare our American specimens. Dr. W . S. Thayer saw A. macu-
Upennis in Grassi’s laboratory in Italy, and on his return to this coun-

Fig. 0. — Anopheles quadrimaculalus: Adult; male at left, female at right— enlarged (original).

try told the writer that he thought the two forms identical. The
question has now been definitely settled by Mr. F. V. Theobald, of
England, who is monographing the mosquitoes of the world for the
British Museum, and who writes us under date of May 28, 1900, that
he has studied a large series of A. qiiadrimaculatus received from
Canada and that “they exactly tally with A. maculdpennis.”

LIFE HISTORY OF ANOPHELES QUADRIMACULATUS.

The adult. — The accompanying illustrations (figs. 6, 7, 8) will show
very well the general appearance of the adult insect. It is a rather

33

Large mosquito and is very blood-thirsty. It is attracted to the house
in numbers. The differences between the males and females are well
brought out in the illustrations, and the striking feathery antennae and
palpi of the male render it very conspicuous. The wing markings and
the color of the palpi differentiate this species from our other species of
Anopheles, and the long palpi of the female at once distinguish it from
all species of Culex.

Fio. 7.— Resting positions of Culex (nt left) and Anopheles (at right), enlarged (redrawn from a rough
sketch published in the British Medical Journal).

Hesting position. — Owing to the publication of a field sketch made
at Sierra Leone by a member of the Ross expedition, and which is
here reproduced, the writer has been much interested in watching the
resting positions of the adult insects. He finds that when resting upon
a horizontal surface — such as the ceiling of a room or the covering of
the breeding jars — the insect clings with its four anterior legs in a
nearly perpendicular position, its beak thrust forward toward the sur-
face to which it clings. The hind legs are frequently in motion, but
as a rule hang downward with more or less of a bend at the knee joint
(femero-tibial articulation). When resting upon a perpendicular sur-
face, however — such as the side wall of a room or the side of a breeding
jar — the body is held only at a comparatively slight angle from the
surface. Sometimes it is nearly parallel with the surface. At other
times it assumes an angle of 10° to 20° (occasionally even as great
an angle as 30° to 40°), the proboscis being held nearly in a line with
the body. Here again the insect supports itself by the four anterior
legs, the hind legs dangling down with more or less of a bend at the

3949 3

34

knee. This position is common to both males and females, and is illus-
trated at tig'. 8. When the body is held parallel it will generally be
found that one of the middle or hind legs has been broken otf. They
are very delicate and readily break.

Fig. 8. — Actual resting positions of A. quadrimaculatus on a horizontal ceiling and on a side wall.

drawn from life — enlarged (original).

The writer has taken the liberty of having fig. 9 engraved from a
drawing sent him by Mr. C. O. Waterhouse of the British Museum.
Mr. Waterhouse made the drawing himself and wrote: “Whatever

...... ■■vwvffPWMM/m

Fig. 9.— Anopheles at left, Culex at right— enlarged (drawn by C. 0. Waterhouse).

may be the attitude of Anopheles, it is all in one line. Culex is angu-
lar, humpbacked.”

Note of female. — The peculiar hum of the mosquito is well-known.
There is a distinct difference between the hum of Anoplieles quadrima-

35

culatus and that of the common species of Culex in that the former is
noticeably lower in tone. The note of Culex as it approaches the ear

Fig. 10 .—Anopheles quadrimaculatus : Group of 44 eggs deposited by a single female as
they appear resting naturally on the surface of the water — enlarged (original).

is high in pitch ; that of Anopheles is certainly several tones lower
and of not so clear a character. In quality it is something between the
buzzing of a house fly and the note of Culex. Mr. Pratt states that he
can at once distinguish the two genera in
this way as he is sitting reading in the
house, and the writer feels quite sure after
listening to them in breeding jars that the
statement is correct.

These observations have been made with
an abundance of material, nearly 100 adults
having been under observation.

The eggs. — The well-known and often-
mentioned boat-shaped masses of eggs of
Culex are not even remotely resembled by
the Anopheles ovipositions, and the indi-
vidual eggs are equally dissimilar. In the
accompanying illustration (fig. 10) the egg-
mass of Anopheles is illustrated for com-
parison with fig. 1. In Culex from 200 to
400 eggs are laid in a mass ordinarily shaped like a pointed ellipse, con-
vex below and concave above, all the eggs perpendicular, and stuck

Fig. 11. — Anopheles quadrimaculatus:
Egg from below at left, from above
at right — greatly enlarged (origi-
nal).

36

closely together at the sides l>y some gummy secretion, and arranged
in rows. I he mass with Anopheles, however, is laid loosely upon the
surface of the water, each egg lying upon its side instead of being
placed upon its end as in the egg mass of Culcx. They are not attached
together except that they naturally float close to each other and there
are from 40 to 100 eggs in each lot. In Oulex jpungens the individual

egg

is 0.7 mm. long and 0.16 mm. in diameter at the base. It is

slender, broader, and blunt at the bottom, slenderer and more pointed
at the tip. The tip is always dark grayish brown in color, while the
rest is dirty white. The egg of Anopheles when seen from above is
of a rather regular elliptical outline, the two ends having practically
the same shape; seen from the side, it is stronglj" convex below and
nearly plane above; seen from below, it is dark in color and when
examined with a high power is seen to be covered with a reticulate
hexagonal sculpturing. At the sides, in the middle, there appears a
clasping membrane with many strong transverse wrinkles. Seen from
above, the egg is black except for a clasping membrane which nearly

Fig. 12 .—Anopheles quadrimaculalus: Newly hatched larva— greatly enlarged (original).

meets on the middle line in the middle third of the bod}", but retires to
the extreme sides for the anterior and posterior thirds. At each end
the color is lighter, with a group of from 5 to 7 minute dark circular
spots. It is 0.57 mm. long. Eggs laid April 26 hatched April 30.
Others laid May 13 and 14 hatched May 16 and 17.

The larva. — The larva is quite as unlike that of Oulex punqens as
is the egg. It differs in structure, in its food habits, and in its cus-
tomary position so markedly that it can at once be distinguished with
the utmost ease. The larva of Culex, it will be remembered, comes
to the surface of the water to breathe, thrusting its breathing tube
through the surface layer and holding its body at an angle of about
45 degrees with the surface of the water. While in this position its
mouth parts are in motion and it is taking into its alimentary canal
such minute particles as may be in the water at that depth, but these
are naturally few in number and the larva descends at frequent inter-
vals toward the bottom to feed. The want of oxygen, however, causes
it to wriggle up again to the surface at very frequent intervals. Its

37

specific gravity seems greater than that of water, so that it reaches the
surface only by an effort, and the writer has already pointed out in the
case of C. pungens that when the larva becomes enfeebled and is not
strong enough to wriggle up to the surface it drowns. Feeding as it
does at the bottom upon the heavier particles which sink, its specific
gravity is explained. The larva of Anopheles guadrimaculatus , how-
ever, habitually remains at the surface of the water. Its breathing
tube is very much shorter than that of Culex and its body is held not
at an angle at the surface, but practically parallel with the surface and
immediately below the surface film, so that portions of its head, as
well as its breathing tube, are practically out of the water. Its head
rotates upon its neck in a most extraordinary way, so that the larva

Fig. 13. — Anopheles quadrimaculatus and Culex pungens: Half-grown larva at left and in center, in
comparison with half-grown larva of Culex pungens at right (figure at left has been cleared) —
greatly enlarged (original).

can turn it completely around with the utmost ease and feeds habitu-
ally with the under side of the head toward the surface of the water,
whereas the upper side of the body is toward the surface. In this cus-
tomary resting position the mouth parts are working violently, the
long fringes of the mouth parts causing a constant current toward the
mouth of particles floating on the surface of the water in the neigh-
borhood, which thus gradually converge to this miniature maelstrom
and enter the alimentary canal. The spores of algie, bits of dust,
minute sticks, bits of cast larval skins, everything in fact which floats,
follow this course, and, watching the larva under the microscope, they
can plainly be seen to pass through the head into the thorax until they

38

arc obscured by the dark color of the insect’s back. Occasionally too
large a fragment to be swallowed with ease clogs the mouth. Some-
times it enters the mouth and sticks. In such cases the head of the
larva revolves with lightning-like rapidity and the fragment is nearly
always disgorged, although sometimes it is swallowed with an evident
effort. Since the Anopheles larva feeds only upon these light floating
particles, its specific gravity is nearly that of the water itself and it
supports this horizontal position just beneath the surface film with

comparative ease, and in fact without effort, the tension of the surface
— film itself being

hardly needed to
hold it. It requires
an effort in fact for
the Anopheles larva
to descend (which it
apparen tly never
docs up to the period
of the final larval
stage, except when
alarmed), while it
requires an effort
for the Culex larva
to ascend.

Structurally the
differences between
the h a 1 f - g r o w n
larvae of Culex and
Anopheles are well
shown at figs. 13, 14,
and 15. The great
size of the head of
Culex, as contrasted
with the small head
of Anopheles is a

Fro. 14.— Figure at top, half grown larva of Anopheles in feeding posi-
tion, just beneath surfaee film. Figure at bottom, half grown larva
of Culex in breathing position — greatly enlarged (original).

most striking differ-

ence. The very
long r espi rato ry

siphon (as Miall calls it) of Culex contrasts markedly with the short
one of Anopheles. The arrangement of the hairs is entirely different,
the branching of the hairs of Anopheles, as contrasted with the simple
hairs of Culex and the little paired star-shaped (apparently branchial)
tufts on the dorsum of Anopheles are entirely absent with Culex. The
flaps at the tail end of the body are similar in number, but are held in
a somewhat different position.

39

Tho larvae first studied — those which hatched from the eggs on
April 30 — grew very slowly for a number of days. This was partly
owing to cool weather in the early part of May, and partly, I believe,
to the absence of proper food. They were reared in glass jars of water,
with sand at the bottom and a willow twig rooting in the sand. As
above noted, they
swallowed every
small particle floating
on the surface of the
water, and the dark
coloration shown in
fig. 14 Avas largeh'
due to the fact that
most of these food
particles Averc dark
colored. About the
10th of May, the
larvae having passed
through tAY'o molts,
a small quantity of
the green algae grow-
ing on the lily ponds
on the Department
grounds was placed
in the jar. 1 The larvae
commence to thrive
much better, greAV
rapidly, and the gen-
eral color of the body
changed to green.

The description of
the habits given
aboAre held Avell until
after the last molt
preceding the change
to pupae. In this final
larval staige, as shoAvn

in tig. 15, tne diameter Fiu. 15. — Anopheles qaadrinuwulalus: Full grown larva in feeding
of the thorax became position, seen from above (head reversed, in feeding position);
, , . dorsal side of head above at right— greatly enlarged (original).

much greater in com-

parison Avith the rest of the body. The larva was less marked, more
inconspicuous, and altered its feeding habits to some extent. After

'These algaj were studied by Mr. A. F. Woods, of t lie Division of Vegetable Phys-
iology and Pathology, who informed me that the larger part belong to a species of
the genus CEdogonium, but that there was also quite a large amount of a species of
Cladophora, with some Spirogyra. There was also some of the blue green Oscilaria.

40

remaining at the surface of the water, feeding, as before, upon floating
particles for some time, it would wriggle violently and descend to the
bottom, where it would remain frequently as long as two minutes
before reascending to the top. Its appetite was. evidently so great
that it was not satisfied with the floating particles, and when it descended
to the bottom it mouthed the particles of sand, evidently swallowing
the slime on the little stones and frequently even picking up quite a
a large sand pebble and then dropping it again. In this stage the indi-
vidual which grew most rapidly remained only four days, and trans-
formed to pupa on the morning of the 17th, after a larval existence of
sixteen days. The accompanying figures of the larvae have been drawn
with such care that detailed description will be unnecessary. They
were drawn from life under the compound microscope. Some of the
structures are puzzling, notably the organs occuring on the dorsum of
the abdominal segments, shown most plainly in fig. 15, and which look
as though they might be spiracles until they are examined under a high
power in the cast skin. The writer does not care to risk an expression
of opinion as to their function, although possibly it is known, and they
possibly occur in other aquatic dipterous larvas. In the early stages of
the larvas they resemble minute branchial tufts, but no tracheal con-
nection has been found.

The pupa.— The accompanying figure (fig. 16) well represents the

Fig. 16.— Pupa of Culex pungens at left; pupa of Anopheles quadrimacuktlus at right — greatly enlarged

(original).

differences between the pupa of Culex and that of Anopheles. In this
stage the insects of the two genera are not so markedly different as in
the larval stage. Structural differences need not be described, as they
are sufficiently shown in the illustration. The eye will at once be
caught by the difference in position, the pupa of Culex resting in a
more perpendicular attitude than that of Anopheles, and the marked
difference in shape between the respiratory siphons, which issue from
the thorax instead of from the anal end of the abdomen, will at once

41

be noticed. The pupa of Anopheles is quite as active, when disturbed,
as is that of Culex. If one touches the near-by surface of the water
with the finger the pupa at once wriggles violently away, returning
shortly to the surface for air.

The duration of the pupal stage in Anopheles varies according to the
weather. Five days was the minimum observed during J une, although
several specimens remained in this stage for ten days. The adults issue
as do those of Culex.

The entire life round, therefore, of Anopheles quadrimaculafais in
the generation studied by the writer is as follows: Egg stage, three
days; larval stage, sixteen days; pupal stage, five days; making a total
period in the early stages of twenty-four days. It should be stated,
however, that during the early larval existence toward the end of May
there occurred nearly a week of cool weather, so that it is certain that
in the hot season in July and August the growth and transformations
will be more rapid. It wTill be remembered that the writer traced
Culex pungens through an entire generation in the latter part of June,
1895, in ten days.

NATURAL BREEDING PLACES OF ANOPHELES.

Having accomplished the preliminary work of studying different
stages of growth of Anopheles by breeding from captured females, we
were enabled to become familiar with the larvae and pupae so as to
recognize them readily and it was then not difficult to find the natural
breeding places. The first breeding place discovered was in Maryland,
and the larva? found there were those of what is probably A. puncti-
pennis. They closely resemble the corresponding stage of A. quad-
rimaculatus except in the maeulation of the head. A figure of the
head of this form is shown here (fig. 17) in order that it
may be compared with the corresponding figure of A.
quad/rim aculatus shown in fig. 15. This first breeding
place of Anopheles was a small permanent stream run-
ning through the woods which had here and there broad-
ened out into little shallows, and in these shallows the
Anopheles larva? were found resting at the surface of fig. n.— Anopheles
the water, and occasionally darting from one spot to vuncUpcn «£>.•
another. All of these little pools 'were abundantly sup- grown larva from
plied with alga?, and from specimens brought in Mr. above— enlarged
A. F. Woods has found that they belong to the genus
Mougeotia. There were also many Diatoms present. The next natural
breeding place found was in pools about a disused spring in Virginia.
At the sides of the spring were several more or less permanent pools
of considerable depth (8 to 10 inches). Here the larvae of A. quad-
rimacidatus were found. Alga? also occurred here and Mr. Woods has
determined them as belonging to the same genus Mougeotia. The

42

temperature of this water was 18° C. The third locality was an okl
canal bed so nearly dried out after a season of drought that the water
lay in rather small puddles. In this case the water was very foul and
algae of the genus Lyngbya were present. The temperature of this
water was 25° C., and the conditions were those of extreme stagnation.
The first locality was discovered by the writer in company with Mr.
Pratt and the second and third were found by Mr. Pratt. Later, the
writer in company with Mr. Busck and Hospital Steward Smith, found
empty pupa skins of A. quad/rimaculatus in a dried up surface pool at
the Washington Barracks, at a time when malaria was very prevalent
among the troops. I am informed by Dr. Thayer, of Baltimore, that
Dr. Lazear found A. punctipennis breeding in a stone quarry near
Baltimore, in the summer of 1899. Ross found in India that while the
species of Culcx generally bred in vessels of water around the houses,
the species of the genus Anopheles bred in small pools of water on
the ground. This point was made the subject of a special investiga-
tion by the expedition of the Liverpool School of Tropical Medicine
to Sierra Leone. While Culex larvae were to be seen in almost every
vessel of water or empty gourd or flowerpot in which a little rain
water had collected, in onl}r one case were Anopheles larvae found in
such receptacles. On the other hand, they occurred in about 100
small puddles scattered throughout the city of Freetown — puddles
mostly of a fairly permanent description, kept filled by the rain, and
not liable to washing out during heavy showers. It was noticed also
that the larvae seemed chiefly to feed on green water weed.

In the interesting and important paper by Dr. J. W. W. Stephens
and Mr. S. R. Christophers entitled “The distribution of Anopheles
in Sierra Leone,” published in the report of the malarial committee of
the Royal Society, July 6, 1900, it is stated that" at Freetown not
only do the larvae of Anopheles exist in the small pools in the rocks,
but also in the pools by the sides of streams and in certain small
drains, and that in the dry season, in the absence of the rock pools,
Anopheles breeds freely in streams and drains; also, in the dry season,
the adults exist in most parts of the town in dwellings, especially in
overcrowded native huts and native quarters, ready to lay their eggs
when pools appear. It is interesting to note, from this latter obser-
vation, that the authors of the paper recommend the destruction of
dirty huts and the prevention of excessive overcrowding. Outside of
the city, in the “bush,” Anopheles larvae were present throughout the
whole district. In the mountain streams, wherever there were suitable
pools, multitudes of larvae existed. In tracing the mountain streams,
occasionally for a half mile or so, they found no larvae, but then a
rock pool occurred, and there they were again found in numbers. At
Son go and Mabang they were able to detect Anopheles larvae in the
swamps. They were not present in the main swamp water on account

43

of the innumerable small fish, but were occasionally observed in small,
isolated pools on the mud, and were still more common in small pools
at the edges of swamps. It is a noteworthy fact that they did not
occur in swamp pools in such numbers as in the streams and rock
pools among the hills of Sierra Leone. “These rock pools would
appear to be the most suitable conditions for the breeding of
Anopheles.”

The avidity with which Anopheles larvse under observation in
Washington fed upon alga; spores of the genera previously mentioned,
and the character of the breeding pools found here, indicate that with-
out doubt similar conditions will prevail generally in this country, and
Anopheles will always be found to breed most abundantly in fairly
permanent stagnant pools of water uninhabited by fish, but more or
less covered with green scum.

OTHER SPECIES OK ANOPHELES.

As appears from the synoptic table on previous pages, we have in
the United States, so far as ascertained, three recognized species of

Fig. 18. — Anopheles punctipcnnis: Female, with male antenna at
right, and wing tip showing venation at left— enlarged (original).

this genus. A. quad/nmaculatus has just been figured in all its stages,
and the accompanying illustration (fig. 18) shows very well the beautiful

44

species known as A. punctipennia Say.
be rarer than the other two and has been

A. crucians (tig-. 19) seems to
taken only in a few instances.

Fig. 19. — Anopheles crucians: Female — enlarged (original)

DISTRIBUTION OF THE SPECIES OF ANOPHELES IN THE UNITED STATES.

Anopheles crucians Wied.

Habitat: District of Columbia, April 27 (Pergande); Georgia (Nat. Mus.); New
Orleans, La., June 28 (Veazie), November (Thayer); Richmond, Va. (Slosson).

Anopheles punctipennis Say.

(Considered by Wiedemann to be the same species as his Anopheles crucians, but
the two are certainly distinct. )

Habitat: Castleton, Yt. , February 1 (temperature 6° F.); Beverly, Mass., Sep-
tember 19, October 2; Cambridge, Mass., June 16, September 30, October 20
(Nat. Mus.); Charlton Heights, Md., March 31, November 17 (Pratt); District
of Columbia, June 6 and 7, October 15, 25, and 31 (Pergande); Philadelphia, Pa.,
October 12 (Johnson); Ithaca, N. Y., April 17, August 28 (Comstock); Illinois,
October 16 (Nason); Texas (Nat. Mus.); Mesilla, N. Mex. (Cockerell); Port-
land, Jamaica (Johnson) ; Middletown, Conn. (Davis) ; Summit, N. J., April 26
(Howard); Roanoke, Va., October (Thayer); St. Elmo, Va., May, June (Pratt);
Brazos River, Tex. (Woldert); Baltimore (Thayer and Lazear); Walbrook,
Md. (Thayer and Lazear); Onaga, Kans. (Creveeoeur).

Anopheles quadrimaculatus Say.

Habitat: Berlin Falls, N. H., August (Nat. Mus.); Ithaca, N. Y., January, July
31, November 28 (Comstock) ; Lakeland, Md., Augusts; Charlton Heights, Md.,

45

Novembe 24 (Pratt) ; District of Columbia, July, October 15, November 2 and
14 (Pergande); Illinois, September 10, October 10 (Nason); St. Anthony Park,
Minn., December 11 (Lugger); Tick Island, Fla., May 12 (Johnson); Texas
(Nat. Mus. ) ; Oneco, Fla., May 26 (Gossard) ; Roanoke, Va., October (Thayer) ;
Newport News, Va., October (Thayer); St. Elmo, Va., April, May, June, July
(Pratt); New Orleans (Thayer); Sparrows Point, Md.,and vicinity (Thayer
and Lazear); Middletown, Conn. (Davis).

THE GENUS PSOROPHORA.

But one species, P. ciliata, of the genus Psorophora is known in
the United States. This is well illustrated in the accompanying
figure (fig. 20). Although this insect, as indicated in the synoptic

tables, is really yellowish in color, yet the general effect when one
glances at it, or sees it flying, is that it is very dark, almost black.
The wings are not really spotted or infuscated, but the very numerous
dark scales on the main veins make the wings appear dark. They are
also when seen in certain lights prismatic in color effect. The palpi
of the female are nearly half as long as the beak, and the beak itself

46

is very stout. The most striking feature of this insect, however, is
the curious series of erect close-set hairs or scales on the legs, which
distinguishes it at once from other mosquitoes. This mosquito is
widespread in the United States, and we have specimens from Dorches-
ter, Mass. (Nat. Mus.); Washington, D. C. (Chittenden); Westfield,
N. J., July 2 (Johnson); Illinois (Nason); Brooklyn Bridge, Ky., June
23 (Carman); Lincoln, Nebr., July and August (Bruner); Los Angeles,
Cal. (Coquillett) ; San Diego, Tex., May 15 (Schwarz); Florida, July
(Nat. Mus.); Hastings, Fla., July (Dept. Agric.); New Orleans,
August, (Veazic). A rather large series was captured in June of the

•Pig. 21 . — Megarhinus rutilus: Pemale — enlarged (original),

present year at St. Elmo, Va., by Mr. Pratt. The writer felt certain
that he would be able to follow out the life history of this species from
the living material captured by Mr. Pratt. Females were placed alive
in breeding jars under conditions which had repeatedly been successful
with Culex and Anopheles, but no eggs were obtained. The breeding
habits, therefore, may be different from those of the other two genera,
and the biology of this form is an interesting and important point for
future investigation. As elsewhere stated, the possible relations
between Psorophora and the HfematamGebfe deserve early investigation.

47

THE GENUS MEGARHINUS.

This is the other genus (tig. 21), the species of which are more or
less abundant in the South, which should be investigated by Southern
observers in regard to its possible connection with malaria. As indi-
cated in the synoptic table, the mosquitoes of this genus are readily
distinguished by the curved beak, which is also well shown in the draw-
ing. They are especially distinguished also by their metallic greenish
or bluish coloration. Nothing is known of the life history of the mos-
quitoes of this genus, and the species known to occur in this country
are distributed as follows, so far as our records go:

Megarhinus ferox Wied.

Habitat: District of Colombia, August 22 (Pergande); (Georgia according to
Walker’s list).

Megarhinus hjemorrhoidalis Fabr.

Habitat: (Cayenne and Cuba according to Osten Sacken’s catalogue).
Megarhinus portoricensis Roeder.

Habitat: Benoit, Miss., July 18 (Hine).

Megarhinus rutilus Coq.

Habitat: North Carolina; Georgiana, Fla- (Nat. Mus.).

TnE GENUS AfiDES.

The mosquitoes of this genus (fig. 22) are minute forms, insignificant
in color, and the only one of which we possess specimens, viz., A. sap-
pldrirma, is shown in the accompanying figure. We have received it

48

only from Ithaca, N. Y., through the kindness of Prof. J. H. Corn-
stock. Another species, A. fwcus , is said by Osten Sacken to occur
at Cambridge, Mass.

THE NATURAE ENEMIES OF MOSQUITOES.

The late Dr. Robert H. Lamborn, of New York and Philadelphia,
while engaged a number of years ago in building the Lake Superior
and Mississippi Railroad, fell in with a great many mosquitoes. He
often, “with a sentiment of gratitude,” as he expressed it, looked
through his mosquito veil at the dragon flies which collected in the
open spaces among the pine trees. 4 ‘ They darted from side to side,
like swallows in a meadow, but with amazing rapidity, and at every
turn a mosquito ‘ceased from troubling.5” This gave Dr. Lamborn
the idea that perhaps dragon flies might be domesticated and utilized
to destroy mosquitoes along the New Jersey coast and elsewhere; and
so he offered prizes for the three best essays regarding methods of
destroying the mosquito and the house fly, especially designating the
dragon fly for careful investigation. The successful essays — by Mrs.
C. B. Aaron, Mr. A. C. Weeks, and Mr. William Beutenmiiller — were
published by Dr. Lamborn in a volume entitled “ Dragon-Flies vs.
Mosquitoes. The Lamborn prize essays.” The essays were all excel-
lent. Here, however, they are mentioned, by the way, in connection
with the group of the best-known natural enemies of mosquitoes,
namely, the dragon flies. It is needless to say that none of the essays
were able to solve the problem of a practical breeding, on a large
scale, of dragon flies for mosquito extermination, and, in fact, the
whole subject of the natural enemies of the mosquito is of little
practical importance. It is sirnpty a matter of general interest.
Dragon flies, as adults, feed upon adult mosquitoes, just as they will
upon all other insects which they are able to capture and devour.
Dragon flies, as larvae, feed upon the larvae and pupae of mosquitoes,
although other and larger and less active aquatic insects and small flsh
form the bulk of their food.

The extreme activity of both larvae and pupae of mosquitoes is a
necessary factor in their struggle for existence, since stagnant pools
of water fairly swarm with predatory animal life. The larva of one
of the water beetles of the family Hydrophilidae eats hundreds of
other insects in the course of its existence, and the larvae of mosquitoes
do not escape entirely, although by their extreme activity they stand
a better chance than do other more sluggish species. A small pool of
water on the Department grounds at Washington is situated near a
manure pile, and the water is colored dark brown by the drainage
from the manure. The pool is kept by Mr. Saunders, the superin-
tendent of the grounds, for the purpose of securing manure water
for some of his plants. It is, at all times through the summer,

49

swarming with the larvse of Oulex pungens , C. stimulcms , and f7.
turbans / also with the larva of an Ephydrid — Brachydeutera a/rgentata
Walk. — and with the larva of an Ephemerid of the genus Csenis, and
other aquatic species. A number of specimens of Hydrophilid larvse
were found by the writer in this pool. They fed upon the other
aquatic insects with avidity, and three of them were placed in a large
battery jar with about a half gallon of this water, teeming with insect
life and containing apparently some hundreds of the mosquito larvse
and many of the others just mentioned. These three Hydrophilid
larvse, in the course of a week, practically devoured all of the other
animal life in the jar. Only two male mosquitoes and one female suc-
ceeded in reaching the adult stage.

No one can realize the intensity of the struggle for existence which
is going on in a stagnant pool until he forces himself to the seemingly
rather unpleasant occupation of lying down by its side and watching
with a large hand lens the various forms of life with which the water
is swarming. Aside from the larvse of the dragon flies and the preda-
tory larvae of the three great families of aquatic beetles, namely, the
Dytiscidie, the Hydrophilidae, and the Gyrinidae, there are aquatic
neuropteroid insects which are predatory and which feed upon
mosquito larvse as well sis others, like those of the genus Hydro-
psyche; and there are aquatic Heteroptera which are silso predatory.

Aside from insects, there are many other natural enemies of mosqui-
toes. Many fish eat their larvae and pupae, and such night-flying birds
as nighthawks and whip-poor-wills, and bats as well, destroy the adults.
Harvey (American Naturalist, 1880, p. 896), quoted by Mrs. Aaron,
found 600 mosquitoes in the crop of a nighthawk.

REMEDIES AGAINST MOSQUITOES.

Remedies m houses and the prevention of bites. — Of the remedies in
use in houses the burning of pyrethrum powder and the catching of
mosquitoes on the Avails in kerosene cups are probably the best, next
to a thorough screening and mosquito bars about the bed. In burning
pyrethrum powder it is well to moisten the powder sufficiently with
water so that it can be molded roughly into little cones about the size
of a chocolate drop. These cones are placed on a pan and dried in
the oven. If ignited at the apex the cones smolder slowly, giving off
an odor not unlike that of the prepared punk which boys in this
country use to light firecrackers. Two or three of these cones burned
in a room in the evening Avill give relief by stupefying the mosquitoes.
This smoke appears to be perfectly innocuous to human beings. The
writer has breathed it evening after evening without the slightest per-
ceptible ill effect. The, method of catching mosquitoes on the Avails
Avith kerosene in cups is iioav in frequent use in different parts of the
3949 4

50

country. No one seems to know who invented it, but the writer first
saw it in operation some years ago in New Jersey, and was struck with
its simplicity and efficacy. The top of a tin baking-powder box is
inverted and nailed to the end of a stick of sufficient length to reach
to the ceiling. A small quantity of kerosene is put into this impro-
vised cup and the apparatus is pushed up under resting mosquitoes,
which fall into the kerosene and are destroyed. It is the custom in
certain houses to systematically hunt for mosquitoes in the bedrooms
with such an apparatus every night before retiring. .

Camphor rubbed on the face and hands or a few drops upon the
pillow at night will keep mosquitoes away for a time, and this is also
a well-known property of oil of pennyroyal. The use of oil of pepper-
mint, lemon juice, and vinegar have all been recommended as pro-
tectors against mosquitoes, while oil of tar as used against the black
fly in Canada is also used in bad mosquito localities. Strongly cam
phorated vaseline, although recommended, has been found by Dr.
Nuttall to be of scarcely any use in Canada.

One of the London papers, the Daily Telegraph, invited its readers
to send in mosquito remedies of this kind during the summer of 1899,'
and some of the substances recommended were as follows:

Eucalyptol on the skin, with a handkerchief saturated with it placed on the pillow
at night — the result of South African experience. (Arthur E. Edwards.) ^

Carbolated vaseline. (Dr. George Mackern.) ^

One drop of oil of lavender on pillow, and one on the head at night. (A. E. S. )

Tincture of Ledum palustrse. (M. Fisher.)

Piece, of cotton wool soaked in oil of cloves on each side of the bed curtains.
(W. B.)

Anoint skin with 3 parts refined paraffin and 1 part crushed camphor. (W. T.
Catleugh. )

To heal the bites, a drop of liquid ammonia. (P. G. L.)

Eucalyptus oil. ( X. )

Same substance. (Dr. George Cohen.)

Oil of eucalyptus and creosote, each 5 drops, to be thoroughly mixed with 1 ounce
of glycerin. (R. R. P. S. Bowker.)

Place a fine, juicy, uncooked beefsteak near the bed on retiring. (M. M. M.)

A substance with which the writer is not familiar, but which is
spoken of very highly in the interesting paper by the Italians Celli
and Casagrandi in a paper to which we shall have occasion to refer
later in speaking of remedies against the larva, is a yellow aniline color,
referred to in the work of the Italians as Larycith III. They state
that a little of this substance burned will kill the adult mosquitoes
and that this method constitutes the most efficacious means of destroy-
ing them. The Chinese use pine or juniper sawdust, mixed with a
small quantity of brimstone and 1 ounce of arsenic, run into slender
bags in a dry state. Each bag is coiled like a snake, and tied with
thread. The outer end is lighted. Two coils are said to be sufficient
for an ordinary room, and 100 coils sell for 0 cents.

51

Remedies for bites.- — Dr. E. O. Peck, of Morristown, N. J., wrote
to this office last summer stating that he had found glycerin a sover-
eign cure for the bites. Touch the bite with glycerin, and in a few
minutes the pain is gone. According to Dr. Peck it also took the
pain from bee stings. Dr. Charles A. Nash, of New York City, has
recently informed the writer, by correspondence, that whenever a
mosquito bites him he rubs the spot and marks it with a lump of
indigo. This, he says, “ instantaneously renders the bite absolutely
of no account,” whether the application is made immediately, the next
day, or the day after. He has used it since 1878, and lives in a New
Jersey town where, he writes, “mosquitoes are a pest every year.”
He finds the same application to give relief from the stings of the
yellow jacket. Household ammonia has been found by many persons
to give relief.

DESTRUCTION OF LARVAE ANI) ABOLITION OF BREEDING PLACES.

The following paragraphs are quoted from the writer’s article in
Bulletin No. 1:

“Altogether the most satisfactory ways of fighting mosquitoes are
those which result in the destruction of the larva? or the abolition of
their breeding places. In not every locality. are these measures feasi-
ble, but in many places there is absolutely no necessity for the
mosquito annoyance. The three main preventive measures are the
draining of breeding places, the introduction of small fish into fishless
breeding places, and the treatment of such pools with kerosene.
These are three alternatives, any one of which will be efficacious, and
any one of which may be used where there are reasons against the
trial of the others.

“ Kerosene on breeding pools. — In 18!>2 the writer published the first
account of extensive out-of-doors experiments to determine the actual
effect upon the mosquitoes of a thin layer of kerosene upon the sur-
face of water in breeding pools and the relative amount to be used.
He showed the quantity of kerosene necessary for a given water sur-
face, and demonstrated further that not only are the larva? and pupa?
thereby destroyed almost immediately, but that the female mosquitoes
are not deterred from attempting to oviposit upon the surface of the
water, and that they are thus destroyed in large numbers befrre their
eggs are laid. He also showed approximately the length of time for
which one such treatment would remain operative. No originality
was claimed for the suggestion, but only for the more or less exact
experimentation. The writer, himself, as earl}' as 18117, had found
that kerosene would kill mosquito larva?, and the same knowledge was
probably put in practice, although without publicity, in other parts of
the country. In fact, Mr. Id. E. Weed states (Insect Life, Vol. VII,

52

p. 212) that in the French quarter of New Orleans it has been a com-
mon practice for many years to place kerosene in the water tanks to
lessen the numbers of mosquitoes in a given locality, although he knew
nothing that had been written to show that such was the case, and he
says: ‘In this age of advancement we can no longer go by hearsay evi-
dence. 1 Suggestions as to the use of kerosene, and even experiments on
a water surface 10 inches square, showing that the larvae could be killed
by kerosene, were recorded by Mrs. C. B. Aaron in her Lamborn
prize essay and published in the work entitled ‘ Dragon Flies versus
Mosquitoes’ (D. Appleton & Co., 1890). Mr. W. Beutenmuller, also
in the same work, made the same suggestion.

“The quantity of kerosene to be practically used, as shown by the
writer’s experiments, is approximately 1 ounce to 15 square feet of
water surface, and ordinarily the application need not be renewed for
one month. Since 1892 several demonstrations, on both a large and a
small scale, have been made. Two localities were rid of the mosquito
plague under the supervision of the writer by the use of kerosene
alone. Mr. Weed, in the article above mentioned, states that he rid
the college campus of the Mississippi Agricultural College of mos-
quitoes by the treatment with kerosene of eleven large water tanks.
Dr. John B. Smith has recorded, though without details, success with
this remedy in two cases on Long Island (Insect Life, Vol. VI, p. 91).
Prof. J. H. Comstock tells the writer that a similar series of experi-
ments, with perfectly satisfactory results, was carried out by Mr. Ver-
non L. Kellogg on the campus of Stanford' University, at Palo Alto,
Cal. In this case post holes filled with surface water were treated,
with the result that the mosquito plague was almost immediately
alleviated.

“Additional experiments on a somewhat larger scale have been made
by Rev. John D. Long at Oak Island Beach, Long Island Sound, and
by Mr. W. R. Hopson, near Bridgeport, Conn., also on the shores of
Long Island Sound, the experiments in both cases indicating the effi-
cacy of the remedy when applied intelligently. I have not been able
to learn the details of Mr. Hopson’s operations, but am told that the}7
included extensive draining as well as the use of kerosene.

“It is not, however, the great sea marshes along the coast, where
mosquitoes breed in countless numbers, which we can expect to treat
by this method, but the inland places, where the mosquito supply is
derived from comparatively small swamps and circumscribed pools.
In most localities people endure the torment or direct their remedies
against the adult insect only, without the slightest attempt to investi-
gate the source of the supply, when the very first step should be the
undertaking of such an investigation. In ‘Gleanings in Bee Culture’
(October 1, 1895) we notice the statement in the California column
that in some California towns the pit or vault behind water-closets is

53

subject to flushing with water during the irrigation of the land near by.
A period of several weeks elapses before more water is turned in, and
in the meantime the water becomes stagnant and the breeding place of
millions of mosquitoes. Then, as the correspondent says, £ people go
around wondering where all the mosquitoes come from, put up screens,
burn buhach, and make a great fuss.’ Nothing could be easier than to
pour an ounce of kerosene into each of these pits, and all danger from
mosquitoes will have passed.

“In many houses in Baltimore, Md., the sewage drains first into
wells or sinks in the back yard, and thence in some cases into sewers,
and in other cases is pumped out periodically . These wells invariably
have open privies built over them, and the mosquitoes, which breed in
the stagnant contents of the sinks, have free egress into the open air
back of the houses. Hence parts of Baltimore much farther removed
from either running or stagnant water than certain parts of Washing-
ton, where no mosquitoes are found, are terribly mosquito ridden, and
sleep without mosquito bars is, from May to December, almost impos-
sible. Specimens of Culex jpungens captured November 5 in such a
privy as described have been brought to the writer from Baltimore by
one of his assistants, Mr. R. M. Reese.

“Kerosene has been tried by Mr. Reese in one case in Baltimore,
and two treatments of a privy made about May 1 and June 1, respec-
tively, seemed to diminish the numbers of the pest in that particular
house; but without concerted action of all the householders in a given
block (all the houses, be it remembered, being exactly alike in the
method of sewage disposal) no great amount of good could be accom-
plished. With such concerted action, however, there seems to be no
reason why the mosquito plague could not be greatly diminished in
many, if not most, parts of Baltimore at a very small expense. Usually
one well serves two houses, the privies being built in pairs, so that one
treatment woidd suffice for two dwellings.

On ponds of any size the quickest and most perfect method of form-
ing a film of kerosene will be to spray the oil over the surface of the
water.

'‘‘Drainage.— The remedy which depends upon draining breeding
places needs no extended discussion. Naturally the draining off of the
water of pools will prevent mosquitoes from breeding there, and the
possibility of such draining and the means by which it may be done will
vary with each individual case. The writer is informed that an elabo-
rate bit of work which has been done at Virginia Beach bears on this
method. Behind the hotels at this place, the hotels themselves front-
ing upon the beach, was a large fresh-water lake, which, with its
adjoining swamps, was a source of mosquito supply, and it was further
feared that it made the neighborhood malarious. Two canals were cut
from the lake to the ocean, and by means of machinery the water of the

54

lake was changed from a body of fresh to a body of salt water. Water
that is somewhat brackish will support mosquitoes, but water which
is purely salt will destroy them.

“ Practical use of fish. — The introduction of fish into fishless breeding
places is another matter. It may be undesirable to treat certain
breeding places with kerosene, as, for instance, water which is intended
for drinking, although this has been done without harm in tanks
where, as is customary, the drinking supply is drawn from the bottom
of the tank. An interesting case noted in Insect Life (Vol. IV,
p. 223), in which a pair of carp was placed in each of several tanks,
in the Riviera, is a case in point. The value of most small fishes for
the purpose of destroying mosquito larvae was well indicated by an
experience described to us by Mr. C. II. Russell, of Bridgeport, Conn.
In this case a very high tide broke away a dike and Hooded the salt
meadows of Stratford, a small town a few miles from Bridgeport.
The receding tide left two small lakes, nearly side by side and of the
same size. In one lake the tide left a dozen or more small fishes,
while the other was fishless. An examination by Mr. Russell in the
summer of 1891 showed that while the fishless lake contained tens of
thousands of mosquito larvae, that containing the fish had no larvae.

“ The use of carp for this purpose has been mentioned in the preceding
paragraph, but most small fish will answer as well. The writer knows
of none that Avill be better than either of the common little stickle-
backs ( (t aster osteus aculeatus or Pygosteus pungitius). They are small,
but very active and very voracious. Mr. F. W. Urich, of Trinidad,
has written us that there is a little cyprinoid common in that island
which answers admirably for this purpose. This fish has not been
specifically determined, but we hope to make an effort to introduce it
into our Southern States, if it proves to be new to our fauna. At Bee-
ville, Tex., a little fish is used for this purpose, which is there called a
perch, although we have not been able to find out just what the species
is. They soon eat up the mosquito larvae, however, and in order to
keep them alive the people adopt an ingenious flytrap, which they keep
in their houses and in which about a quart of flies a day is caught.
These flies are then fed to the fish. This makes a little circle which
strikes us as particularly ingenious and pleasant. The flytraps catch
the flies and rid the house of that pest. The flies are fed to the fish in
the water tanks and keep them alive in order that they may feed on
the mosquito larvae, thus keeping the houses free of mosquitoes.

“ Artificial agitation of the water. — Where kerosene is considered
objectionable, and where fish can not be readily obtained, there is
another course left open. It is the constant artificial agitation of the
water, since mosquitoes will oviposit only in still water. At San
Diego, Tex., in the summer there are no streams for many miles, but
plenty of mosquitoes breed in the water tanks. Some enterprising

55

individuals kept their tanks free by putting in a little wheel, which is
turned by the windmill, and keeps the water almost constantly
agitated.”

Later use oflcerosme. — Since the publication of the recommendations
just quoted, a great deal of experimental work has been carried on in
different parts of the country, both on a small scale and on large
scales. An unfortunate editorial note published in the American
Naturalist in 1895 states that the writer discovered the kerosene treat-
ment against mosquito larvae, whereas in his first article on the sub-
ject (Insect Life, Yol. Y, pp. 12 to 11) he began with the words: “One
of the most reasonable of the recommendations which have been made
from time to time * * * is the application of kerosene to restricted
and fishless breeding ponds.” The note in the Naturalist was the text,
however, for a sarcastic note in the Revue Scientifique, 1895, Volume
IV, page 729, by a writer named Delbceuf, aimed not only against the
writer, but against Americans in general. He stated that he had used
kerosene as a remedy for fully fifty years, and that its use is referred
to in the Journal Pittoresque for 1847, page 80, where it is spoken of
as something already well known. Since the writer made no claims
to any originality, but simply announced exact experimentation upon
a somewhat large scale, the matter may rest very comfortably where
it is. But it is interesting to note here that as long ago as 1812, in a
work published in London under the title “Omniana or Horai Otio-
siores,” a collection of odds and ends of all kinds, the following sugges-
tion is made:

The mosquito, which is of all the race of flies the most noxious, breeds in the
water. Might it not be possible at the seasons when they emerge and when they
deposit their eggs upon the surface to diminish their numbers by pouring oil upon
great standing water and large rivers in those places which are most infested by
them?

The writer is indebted to Mr. D. C. Clark, of Baltimore, for this
interesting reference.

During the past few years kerosene has been rather extensively used
at many places in an effort to limit the mosquito supply. As already
pointed out, there are many places where the source of mosquito sup-
ply is definitely limited and easy of treatment, and in such cases on
account of the cheapness of kerosene it will be the best means of erad-
ication. In other places where communities are surrounded with
swamp land or in the case of extensive sea marshes kerosene can be
practically used in connection with other and more elaborate measures,
,, comprehending, as a rule, dyking and draining. At a relatively slight
expense, however, a country club on Staten Island has during one sea-
son practically stopped the breeding of Culex pun gens in ponds and
marshes in the vicinity by the use of kerosene alone. This substance
has also been used with good effect by the Town Improvement Society

56

at Summit, N. J., in woodland pools and swamp land, and its use on a
large scale is being attempted the present year in the vicinity of a arge
town on Long Island. Dr. A. D. Hopkins, of Morgantown, W. Va.r
tells the writer that about ten years ago an extensive pumping station
was located near the river bank where the oil pipe line crosses a mile
above Morgantown and that the oil frequently escapes out over the
river. Since that time the city has been almost exempt from
mosquitoes.

In 1897, Mr. M. J. Wightman, while interested in developing a new
lesoit known as Midland Beach, had 4 barrels of crude petroleum
scattered over the marshes surrounding the beach. For three weeks
previously the mosquitoes had been unbearable. The employees at
the beach went about with their heads covered with netting, and of
course this had a very discouraging influence upon visitors. The
oiled district covered a radius of half a mile, and Mr. Wightman, writ-
ing in 1899, stated that within three days after the oil was distributed
mosquitoes were rare along the beach. This condition lasted through-
out the season. Recently, owing to a change of management, the
writer is informed that nothing has been done and that mosquitoes
have become plentiful again.

Dr. St. George Gray, of St. Lucia, British West Indies, writes, after
reading Bulletin 4 of this office, that he has tried kerosene in his well
and in the water jars in his yard with the result that one species has
disappeared from his house and that the other mosquitoes give him
very little trouble.

The remedial experiments against mosquito larvae tried by Doctors
Stephens and Christopher at Sierra Leone are given in the reports to
the malaria committee of the Royal Society, London, July 6, 1900.
They selected as the most practical larvicides kerosene (paraffin oil)
and salt. The salt, requiring a very strong solution, was not experi-
mented with extensively. A few handfuls thrown into pools contain-
ing not more than 3 or 4 pints of water produced no effect in three
days. With kerosene the rock pools and small runnells of water were
treated: “The larvicidal effect in the pools was very striking, most of
the larvae being killed in fifteen minutes or less. In many cases again,
besides the larvicidal effect, adult females were found next day killed
by the paraffin on the surface of the pool where they had come to lay
their eggs.” Thus the writer’s 1893 observation on the non-deterrent
effect of the kerosene film on adult mosquitoes and their resultant
destruction before the eggs are laid is confirmed. This has always
seemed to bo a point of great practical value in the use of kerosene.
The final result by the English observers, however, was found to be the
immediate return of the insects on the cessation of the application of
petroleum. An interesting test experiment was made by them upon a
surface drain arising from a spring and running for 300 yards when it

57

entered a brook. The spring was free from larvae, but the drain teemed
with them throughout its entire length. Over this drain kerosene oil
was sprinkled by means of a watering pot. About 4 gallons sufficed to
cover the drain thickly with oil. “The larvicidal effect was imme-
diate, and on the following day no living larvae were seen. Four days
later traces of oil were still present in places. Eight days later small
larvae were present along the whole drain. * * * A weekly appli-

cation of paraffin then would effectually prevent the formation of the
perfect insect in these situations.”

The rapid disappearance of the kerosene covering in this last experi-
ment is quite contrary to the results of our applications made to still
pools of water. This may have been due in part to the fact that there
was more or less of a current in the drain, and may also have been
due to the use of an especially volatile kerosene. The writer is now
advising the use of the grade known as lubricating oil as the result of
the extensive experiments made on Staten Island. It is much more
persistent than the ordinary illuminating oils.

An interesting plan, suggested to the writer by Mr. W. C. Kerr,
of New York, in conversation, to disseminate oil over salt marshes,
was that of putting barrels of oil in the marshes in winter when the
ground is frozen and piercing the barrels with small holes so that the
oil will escape slowly through the following breeding season. The best
method of distributing oil on the surface of water is a practical ques-
tion which each experimenter is apt to settle for himself. The writer
has adopted the plan of simply pouring the requisite quantity of oil
upon the water and allowing it to spread by itself, which it does in the
course of time. The Staten Island and Summit, N. J., people use a
spray pump, but in some ways this seems to the writer not perfectly
satisfactory. A great deal of kerosene is apt to be wasted and the
continuous layer of oil which is desirable is frequently not brought
about. The Liverpool School of Tropical Diseases advises as the
result of the Sierra Leone work that the oil can lie best applied by
smearing the pool with a rag fixed to the end of a stick and dipped in
a pot of oil. “ In this manner a number of pools can be dealt with in
five minutes at the expense of very little oil.”

OTHEK LAKVICIDES.

Pcmnangwriate of potash. — Other substances have been experimented
with. Two years ago many newspapers contained an item concerning
the use of permanganate of potash. As this item was credited to the
Public Health Journal it gained a great deal of credence, and was
afterwards mentioned in an interesting article by Mr. A. C. Weeks,
in the Scientific American. The published note read as follows:

Two and one-half hours are required for a mosquito to develop from its first stage,
a speck resembling cholera bacteria, to its active and venomous maturity. The

58

insect m all its phases may be instantly killed by contact with minute quantities of
permanganate of potash. It is claimed that 1 part of this substance in 1,500 of
solution distributed in mosquito marshes will render the development of lame
impossible; that a handful of permanganate will oxidize a 10-acre swamp kill its
embryo insects, and keep it free from organic matter for thirty days, at a cost of 25
cents; that with care a whole State may be kept free of insect pests at a small cost.
An efhcacious method is to scatter a few crystals widely apart. A single pinch of
permanganate has killed all the germs in a 1,000-gallon tank.

I ho item is so obviously ridiculous upon its face that it would hardly
seem worth while to make any attempt to refute its statements. Nev-
ertheless, it has been so widely read that definite experimentation
seems necessary to set the matter at rest. The unknown author’s
ignorance of the life history of mosquitoes in the opening sentence
need not necessarily imply that ho would not know a good "remedy if
he found one. Careful experiments were undertaken by the writer
m July, 1898, with various strengths of permanganate of potash in
water containing mosquito larvae from one to six days old. It was
found that small amounts of the chemical had no effect whatever upon
the larvae, which were, however, killed by using amounts so large that,
instead of using a ‘'handful to a 10-acre swamp,” at least a wagon
load would have to be used to accomplish any result. Moreover, after
the use of this large amount and after the larvae were killed, the same
water twenty-four hours later, sustained freshly-hatched mosquito
larvae perfectly, so that even were a person to go to the prohibitive
expense of killing mosquito larvae in the swamp with permanganate
of potash, the same task would have to be done over again two days
later.

The same conclusion was subsequently reached, after careful experi-
ment, by Dr. Lederle, of the New York health office, and by the Ital-
ians Cell! and Casagrandi.

Proprietary mixtures. — A number of proprietary and secret mix-
tures recommended for mosquito-breeding pools and which have been
put on the market since the wide-spread interest in the mosquito ques-
tion has sprung up have been tested by the writer, but none have been
found more satisfactory than the cheapest petroleum oil.

Experiments of CelUand Casagrandi. — The most extensive series of
experiments with culicidal mixtures which has been made was con-
ducted by the Italians Celh and Casagrandi, above referred to. They
have tabulated in the “Annali d’ Igiene Sperimentale, Home (Vol. IX,
Fasc. Ill, 1899, pp. 317-358), the results of experiments with many
substances. Referring to petroleum, they say that apart from the
question of the expense, Avhich outside of America is worthy of note,
the action of petroleum in destroying mosquito larva} is not always to
be put in the front rank. Their conclusions are practically as follows:

(1) Of the whole period of the cycle of development of mosquitoes the stages in
which they are most easily destroyed are those of larva; and of the aerial mosquito,
and larva} are most easily killed the younger they are.

59

(2) To kill the larvae, among numerous substances experimented with, there will
have, in decreasing order, culicidal action: (a) Mineral: sulphurous oxide, perman-
ganate of potash with hydrochloric acid, common salt, potash, ammonia, carburet of
lime, corrosive sublimate, chloride of lime, the bisulphites, sulphate of iron or cop-
per, lime, bichromate of potash, and sodium sulphite, (b) Organic: powders of the
unexpanded flowers of chrysanthemum, tobacco, petroleum and oils, formalin,
cresol, certain aniline colors (gallot, green malachite), coal tar. Taking into account,
however, the dose necessary to kill the larvae, the practicability and the price, all of
the mineral and some of the organic substances are excluded, and there remain as
available the vegetable powders, petroleum, and the aniline colors.

(3) To kill aerial mosquitoes, we have odors, fumes, or gases. Among the odors
are turpentine, iodoform, menthol, nutmeg, camphor, garlic. Among the fumes
are tobacco, chrysanthemum powder, fresh leaves of eucalyptus, quassia wood,
pyrethrum powder. Among the gases, sulphuric oxide. It is, however, to be noted
that for these odors, fumes, or gases to exercise their culicidal action they must fill
or saturate the whole ambient; otherwise they produce only apparent death, or at
most only a culicifugal action, which sometimes in houses may be useful in protect-
ing man from being bitten by mosquitoes, and preventing the latter infecting him
when they have sucked the blood of malarious persons.

(4) The problem of the destruction of mosquitoes is experimentally soluble, but
practically it will only be so when economic interests desire it. In this latter sense
it is remarkable that the old larvicidal use of petroleum 1ms not become much diffused
in those places where it is very cheap. The chrysanthemum plants might be grown
on a large scale, this making the malarial place itself produce that substance which
frees it of the mosquitoes that infest it.

(5) The opportune season for killing the larva: is in the winter, when they are in
least numbers in the waters and new generations are not born; this also is the season
for their destruction in houses, for they come here for a warmer abode. Their habits
and places of nesting should be studied to this end. This may not be accomplished
on a large scale as easily as some boast; nevertheless, after the treasures spent by
nations and individuals for preserving vines and vegetation from the oidiiun, the
peronospora, and the phylloxera, we may hope that something may be done for
protecting the life of man from the mosquitoes of malaria.

It will be noticed that they really exclude from further consideration
all substances except vegetable powders, petroleum, and the aniline
colors. By vegetable powders they refer to the powders from the
flowers of plants of the genus Pyrethrum, and their experiments upon
the aniline colors practically center upon the recommendation of the
substance already referred to as the yellow aniline dye which the}' call

Larycith III/’ This color has the property of other aniline colors in
that it is soluble and diffusible in water. The practice recommended
is to make a concentrated solution, which is poured into the pool or
pond to be treated. It is said by the authors that it will destroy all
insect life and fishes, but is harmless to warm-blooded animals; tnus
domestic animals may, without danger, drink from pools being treated.

Just what “Larycith III” will prove to be and whether it will be
available for use in this country unfortunately can not be ascertained
at the present moment. Correspondence has been entered into with
large dye firms in New York who have sent abroad for information.

Dr. Ross, in his article in Nature of March 29, previously referred

00

to, says: “On the whole, the most promising method which suggests
itself is the employment of some cheap solid material or powder which
dissolves slowly, which kills the larvae without injuring higher animals,
and which renders small pools uninhabitable for the larvae for some
months. If, for instance, a cartload of such material would suffice
to extirpate the larvae over a square mile of a malarious town, the
result would be a large gain to its healthfulness. Dr. Fielding-Ould
has lately reported favorably on tar.”

Tar and its compounds. — Again, in the report of the Liverpool
School of Tropical Diseases the following words occur: “Perhaps more
permanent oil than kerosene would be more permanently effective.
Fresh tar dropped in a puddle makes a film like that of oil and has
been favorably reported on. Quicklime has been suggested, and all
these should certainly be tried.”

The writer is rather at a loss to know exactly what is meant by the
expressions “fresh tar” and “tar” in the above paragraphs. He has
conducted an experiment, however, with a substance known to the
trade as “coal tar,” a thick viscid liquid. A few large drops of this
substance were dropped into a glass vessel containing approximately
2 quarts of water in which were more than 100 full-grown larvae of
Culex. All the drops but one sank at once to the bottom, the last one
floating upon the surface for some time. No surface film seemed to
form from the tar, but after the expiration of forty-eight hours the
water was found to be more or less impregnated by the tar, having
turned somewhat darker in color, while the odor of the tar was per-
ceptible. At the expiration of five days nearly all the Culex larvae
were dead; 1 had succeeded in transforming to pupa, and 5 or 6 remained
at the surface enfeebled and dying. Thus more than 95 per cent had
been killed. In the meantime, however, twenty-four hours after the
experiment began, 3 egg masses were laid on the surface of the water
by outside females of Culex. These had hatched in forty-eight hours
more, and on the fifth day, although the original full-grown larvee
were practically exterminated, many young larvee were swarming
actively about in the tar water. They continued to grow and to
remain apparently perfect^ active and healthy, although the odor of
the tar was distinctly perceptible and the color of the water was dark,
and even a thin oily film remained over a portion of the surface.

From this experiment it was plain that the killing effect of the tar
in the preparation used is comparatively fugitive, and it was next
decided to test some of the coal-tar products. The object of this line
of experimentation was not onty to test the suggestions of the English
observers, but also on account of the fact that as almost every com-
munity manufactures its own illuminating gas it was considered an
easy and probably econominal way of securing a mosquito larvicide, if
it should prove to be effective. Coal tar is distilled into various grades

61

of oil, and two of the heavier of these grades were used in the suc-
ceeding experiments. One of these was called “creosote oil,” and was
a rather light oil of a specific gravity of 1.035 at 60° F., and the other,
bearing no name, was somewhat heavier. The experiments were nec-
essarily on a somewhat small scale. Eighty nearly full-grown larvae
of Culex stiinulam and C. perturbans were placed in 3 quarts of water
and one-fourth ounce of creosote oil was poured in at 4.15 p. m. At
5.45 17 pupae and 3 larvae were left alive. The next morning at 9
o’clock it was found that 8 adults had issued over night, but all had
been killed by the creosote. At 3 p. m. of the same day, twenty-three
hours after the introduction of the insecticide, all larvae and pupae were
dead. With the slightly heavier oil, 150 larvae of the same species,
all full grown or nearly so, were placed in 2 quarts of water and three-
sixteenths ounce of the oil was added at 4.15 p. m. At 5.45 all were
dead except 28 pupae and about 30 larvae. The next morning at 9
o’clock it was discovered that 10 adults had issued over night, but had
been killed before flight by the oil. At 4.30 p. m. of the same day all
the larva} were dead, but 10 pupae were still active. On the following
morning, at 9 o’clock, forty-two hours after the application, all larvae
were dead and the adults had issued from the remaining pupae, but
had been caught by the oily film in the act of issuing and had died
upon the surface of the water.

Still another experiment was tried with pupae only. Two hundred
and fifty pupae of the same Culices were placed in 3 quarts of water
and one-fourth ounce of creosote oil was added. Twenty hours later
many of the pupae were still living, but thirty -six hours from the time
of application all were dead, no adults having issued. A check experi-
ment with kerosene was carried on parallel with this last experiment
with creosote, and it was noticed that the action of the kerosene upon
the pupae was much quicker, all dying within forty-five minutes. A
few young larvae, however, in the same jar lived for several hours.

An interesting effect of the application of the creosote in the first
two of these experiments was that it seemed without doubt to hasten
the transformation of the insect. When at 4.15 the creosote was
poured in jars 1 and 2, no pupae were observed, but all larvae were
full grown or nearly so. After fifteen minutes 10 pupae were observed
in jar 2 and 5 in jar 1. Ten minutes later 15 were counted in jar 2
and 13 in jar 1. Twenty minutes later there were 19 in jar 2 and 22
in jar 1. Fifteen minutes later still there were 19 in jar 2 and 22 in
jar 1. Thirty minutes later there were 17 in jar 2 (2 having died in
the interval) and 28 in jar 1. As above stated, over night a number
of adults issued, 10 in jar 1 and 8 in jar 2, and twenty-four hours later
10 more adults issued in jar 1. It must be remarked that the full-
grown larvte struggled violently on perceiving the uncomfortable
presence of the creosote, and as they were just ready to transform this

62

violent struggling evidently assisted in the breaking of the larval skin
leaving the pupa bare. This transformation from larva to pupa is
hardly as interesting as the rapid development of adults, 18 of which
issued within fifteen hours after transformation to pupa, whereas
previously the shortest duration of the pupal state which we had
observed was forty-eight hours. It looks like an effort of nature to
perpetuate the species in the presence of a unique emergency.

On the whole, the result of the experiments with tar and tar oils was
rather unsatisfactory as compared with the heavier grades of kerosene.
The effect of the tar was not permanent, and the effect of the creosote
oils was not as rapid as that of kerosene, and the writer is inclined to
the opinion that the heavier grades of kerosene oils are, on the whole,
preferable, although the effect of the creosote oils is very good, and
the}r can be used to advantage. He is inclined to think that they may
prove to be more permanent, although not quite so rapid in their
effect, than the lighter illuminating oils.

EUCALYPTUS TREES.

In addition to the use of eucalyptus oil on the skin to keep mosquitoes
from biting, the growth of eucalyptus trees is said by certain persons
to drive mosquitoes away, and trees of the genus Eucalyptus have
been especially recommended for planting in malarial regions. Mr.
Alvah A. Eaton, of California, wrote us in 1893 that in portions of
California where the blue gum occurs no other remedy need be sought
for. Further than that, he stated that no matter how plentiful the mos-
quitoes, a few twigs or leaves laid on the pillow at night would secure
perfect immunity. The same year Mr. W. A. Sanders, of California,
sent the following interesting account of the value of eucalyptus trees
in answer to our published request in Insect Life:

I have the largest and oldest grove of trees of Eucalyptus globulus in this part of
California, and have had fifteen years of opportunity to study these trees as insect
repellants, and deem it my duty to respond to your request on page 268 of Insect
Life.

Thirty-three years ago I spent a portion of one summer with a Dr. McConnell, who
had just returned from some years of residence among the Eucalyptus forests of Aus-
tralia. We were in the Sequoia ( Sequoia sempervirens) forest of the coast region of
our State. The mosquitoes were so had that it was nearly impossible to work during
days when there was no wind. The doctor assured me that our common mosquito
was never found in the Australian Eucalyptus forests and swamps, but added, There’s
a ‘ ‘spotted mosquito’ ’ nearly as bad there in some places. He, not being an entomolo-
gist, was unable to tell me whether the “spotted mosquito” was a species of the
genus Culex, or of some allied genus.

The doctor being a reliable, close observer, I determined to test the antimosquito
qualities of the Eucalyptus; so when I began to improve my house here nineteen
years ago, one of the first things I did was to get a lot of eucalyptus seed from Aus-
tralia and plant out a grove oi the trees. The tallest of them are now over 140 feet
tall, and can be seen for 20 miles around. My house stands in the midst of these

63

trees. My irrigating ditch, a dozen feet wide, of sluggish current, runs through the
grove beside the house. There has never a single mosquito larva been seen in the
ditch from where it enters the first shade of these trees to where it emerges from them
200 yards away, while above and below mosquito larva) are plentiful — not imme-
diately below, but some hundreds of yards away,' where the water stands in pools
and becomes stagnant among a growth of black walnuts and cottonwoods.

My live stock pasture in this timber, going into the walnuts and back again under
the eucalyptus shade at pleasure. Frequently when the cows come up at night they
bring a swarm of mosquitoes; occasionally some of them get into the house, but
cause us so little annoyance that we scarcely notice them. Before this ditch reaches
the Eucalypti it runs through a jungle of “fence bamboo” (Arundo vuicrophylla),
where the mosquitoes are so bad that we avoid working there except on the windiest
days. And, though the ditch has more current there, the larva) of mosquitoes are
plentiful in the water till it reaches the Eucalyptus trees, below which point none
are found till it has become stagnant away below them.

People who have camped along the willows of Kings Kiver, only a few miles
away, have come here with faces so blotched and swollen from mosquito bites as to
be hardly recognizable, and have camped in the shade of “Sanders’s gum trees,” as
my grove is popularly allied, for weeks, and declare that they never even heard a
mosquito sing during that time.

To the non-botanical reader I may say that this species of Eucalyptus is very tender
to frost. The coldest weather ever known here, 19° F. above zero, killed thousands
of them.

Dr. NuttaU points out that the planting of eucalyptus trees is not a
sovereign remedy, from the fact that malaria still prevails at Tre
Fontane, outside of Rome, in spite of Eucalyptus plantings. The
mere planting of trees, however, is undoubtedly of use in malarial
districts, since it will modify the condition of drainage of the soil.
In view of Mr. Sanders’s strong evidence it really appears that plant-
ing of eucalyptus trees will be worth while in certain locations, not
entirely (on account of the conflicting and not thoroughly satisfactory
evidence) for mosquito protection, but incidentally for this use as well
as other purposes.

DRAINAGE AND COMMUNITY WORK.

After all, the best of the means which may be adopted against mos-
quitoes will always consist in the abolition of their breeding places.
Small pooLs with stagnant water can be treated, but it is a great deal
better to drain them or to All them up. Swamp areas must sooner or
later be drained. It is perfectly obvious that the sooner this is done
the better from every point of view, not only from that of human
health but from the increased value of real estate in the neighborhood
and from the practical value of the reclaimed land itself. The time is
coining, and rapidly, when this drainage of large swamps will not
remain a matter which concerns the individual owner of the land, but
one for town or county action, and even for States. The report of
T. J. Gardner on the policy of the State respecting drainage of large
swamps, published in the Report of the Board of Health for New York,

64

Albany, 1885, although antedating the recent important mosquito dis-
coveries, is well worth reading by all public-minded persons, and the
annual reports of the State geologist of New Jersey for 1897 and 1898,
in which the reclamation of the great Hackensack Meadows, near J ersey
City, Newark, and Elizabeth, N. J., makes interesting reading along
this line. Work on these marshes has actually been begun. The
solution of this case is taking the form of separate action by cities and
their municipalities, each improving the territory within its corporate
limits. The city of Newark has a tract of 4,600 acres of marsh within
its limits; Jersey City has within its limits 2,086 acres of tide marsh,
and Elizabeth has 2,658 acres. The three cities, therefore, have about
8,700 acres of the 27,000 acres lying between Elizabeth and Hacken-
sack. The sanitary importance of reclaiming these lands is of the
greatest, but the capabilities of the improvement plans are attracting
attention on the part of capitalists and business men, who see in these
tide lands valuable sites for manufacturing, industrial, and commercial
activity.

Even to individual land owners of a community, the drainage of
swamps and the consequent abolition of mosquitoes will in many cases
become well worth while. The writer knows of a town in New Jersey,
with a good elevation, within easy distance of New York, and admirably
adapted for summer residences of New Yorkers, where the mosquitoes
are so abundant as to prevent the rise in the price of real estate. An
examination of the surrounding country has convinced him that if the
large real estate owners were to club together they might, by the
expenditure of a few thousand dollars, largely do away with the mos-
quito plague. Another case which is well worth specific mention, and
the truth of Avhich the writer will vouch for, may best be told in the
words of a correspondent, printed in one of the Flushing papers late
in March:

In the town of Stratford, Conn., where I have resided for the past forty-five years,
we have been greatly plagued by swarms of mosquitoes, so great, in fact, that the
“Stratford mosquito” became a well-known characteristic of Stratford. We have in
the southern part of our town, bordering on the sound, several acres of marsh land
or meadow, which would become periodically overflowed with water in the summer
and a tremendous breeding ground for mosquitoes, and this plague to the town con-
tinued imtil about 1890-91, when a party from Bridgeport, Conn., purchased a large
section of the meadows and began to protect them by a dike, both on the north and
south ends, which shut out the water. In addition to this, numerous drain ditches
were made, which helped to carry the water away. The result of this work made
the land perfectly dry and spongy, so that after a rain no pools collected on the sur-
face of the meadow and prevented the creation of the mosquitoes. The transforma-
tion was so remarkable that people outside the town would hardly believe that it
had been effected, and a year or two later the town voted a special appropriation oi
$2,000 to the party who undertook to build the dike and render the meadows mos-
quito proof. It had also the effect of placing on the market a large tract of land
elevated from the sound for residences, and as many as 25 summer residences have

65

been built upon this land bordering the sound, and are increasing each year. They
are free from mosquitoes, so that the operation shows the economy and the benefit
that will result by using some means for eliminating the mosquito-breeding pools.

As to community work, we must not fail to mention the interesting
fact that the city of Winchester, Va., is reported to have passed an ordi-
nance requiring property holders to treat drains and stagnant pools of
water with kerosene during the summer season. Winchester is a town
of high elevation and has for a long time enjoyed a reputation among
Virginians as a cool place to spend the summer. Mosquitoes, we are
told, however, made their appearance there a few years ago, with the
effect that summer visitors became fewer and fewer The passing of
the city ordinance was deemed a matter of public policy and met with
general approval. Police measures of this kind may not be inadvis-
able under certain circumstances. Surely in such instances as the
Baltimore case, mentioned in previous pages, it seems entirely appro-
priate that the board of health should be called upon to enforce kero-
sene treatment.

3949 5

t

APPENDIX.

AN EARLIER ACCOUNT OF THE LARVA OF ANOPHELES.

Just as this manuscript was about to be sent to the printer the
writer’s attention was called to ar paper b}^ F. Meinert, entitled “Die
encephale Mygelarver” (Sur les larves encephales des Dipteres; leurs
moeui s et leurs metamorphoses), K. Danske Videnskabernes Selskabs
Skrifter (Copenhagen), iii, pp. 3(3—493, Pis. I— IV (1886), in which,
among other observations, he gives a brief statement concerning Ano-
pheles which is sufficiently interesting to translate:

“Anopheles— In the ‘Observations d’Histoire Naturelle’ of Joblot
one finds a description of this larva, “ Description of a new fish,”
which is rather insignificant, and a drawing which is not badly done.
The larva drawn by Brauer as Anopheles is a larva of Dixa, and those
reported by Fischer d’ Waldheim as C. elaviger are larvae and nymphs
of the genus Corethra, while his nymph is a Tanypus, and his fly an
Anopheles. Aside from this, Gerke has briefly mentioned this larva
in his paper entitled ‘ On the metamorphoses of the dipterous genus
Dixa,’ page 166.

“The larva of Anopheles lives in still waters or in a weak current
with a rich vegetation, in wooded or unwooded regions. It does not
like the shade of great trees, but seeks the sun and the light, as is
indicated by its fresh green color. It does not hibernate, but in mild
seasons it is found in a half-grown condition by the end of March-. In
July or a little later in the course of a summer the second generation
of the full-grown larvae are found, and in 1882, a year when the spring
was very forward, the writer found at the end of October small larvae
which certainly belonged to the third generation; but it was not to be
supposed that these larvae would become full grown, since as they live
at the surface of the water the first film of ice would kill them.

“The larvae hold themselves at the surface of the water, where they
float with the extremity of the abdomen turned toward the bank or
toward the plants which cover the surface. The larva is stretched out
in the water with the respiratory tube at the surface. The larger part
of the abdomen and posterior part of the thorax are submerged, only
a little portion of the prothorax emerging. The head is under water.
The long hairs with which the body of the female is provided on the
sides, on the metathorax, and the first three segments of the abdomen
are of great assistance to it in maintaining a fixed position. It rests
often for a long time immovable and only occasionally changes its
location. Its movements denote a certain apathy or indolence, but at
the same time much prudence and apprehension. When it moves it
66

67

moves rapidly and dives to the bottom of the water. Recovering from
its fright, it rises obliquely to the surface.

“Just as with the larvae of Culex, the larva? of Anopheles live upon
organic microscopic particles which float upon the water, and which are
brought into the mouth by the movements of the rotatory organs.
These organs are much more developed than with the larvae of Culex,
and while they serve, like the former, as a brush or sieve to strain their
food the larvae of Anopheles, like those of Simulium, holding the head
stretched forward, use them to agitate the water. The larva? of
Anopheles present this peculiarity, that in producing these currents,
which they do the greater part of the day, they lie upon the belly
with the under part of the head turned upward. This rotation of the
head is executed with the greatest rapidity; and scarcely, for example,
have the larvae come to the surface to float, when, by a rotation of the
head upon its longitudinal axis, it is turned bottom side upward and
commences to agitate the surface of the water. This agitation is
undoubtedly for the purpose of drawing floating objects surely and
completely into the orifice of the mouth. This, however, is not neces-
sary, for often one sees the larva with its head working in normal
position, mouth organs below, but in general they do not remain in
this position for a long time, and it is only after having turned the
head upward that they seem to work con arnoi'e.

“As a rule the larvae seek their nourishment while the}" are floating
at the surface, but at other times they descend two or three inches
under the water. The}' can rest several minutes in this position with
the head below, after which they come to the surface again.”

This account shows that Meinert knew the larva? very well, and one
can only regret that he did not describe the eggs and the pupa?.

THE MALARIAL EXPEDITION OF THE LIVERPOOL SCHOOL OF TROPICAL

MEDICINE.

This interesting and most valuable report was known to the writer
only by brief newspaper notes until the present bulletin had reached
page proof — too late to insert in proper place several important obser-
vations made by Ross, Annett, Austen, and Fielding-Ould. To-day
(August 13) it has reached him in Volume II of the Thompson Yates
Laboratory Reports (University Press of Liverpool, 1900), and he is
glad of the opportunity to add the following paragraphs quoted from
its pages:

8. METHODS FOR ASCERTAINING DEFINITIVE HOSTS.

The long researches of one of us in India, followed by those of Koch, Daniels, and
the Italian investigators, have given us a very exact knowledge of the life history of
the Ihemamcebida; in gnats, and have shown us how to detect them in the insects
with ease and certainty. It has been noted that in inhospitable species of gnats the
ingested parasites perish within the stomach cavity, whereas in hospitable species
the zygotes escape from that cavity and develop in the tissues, ultimately giving rise
to blasts which are found in the juices and salivary glands of the insect. * * *

68

15. BIONOMICS OK ANOPHELES LARVA?.

We made the following observations:

(1) Eggs. — These are boat-shaped , like those of Anopheles observed in India. They
appear to be laid singly on water, but cohere by their ends, forming typical triangu-
lar patterns, and also adhere to floating objects, the sides of the vessel, etc. We
observed no facts indicating that they are ever laid on solid surfaces. In vitro they
take about twenty-four hours to hatch, but the period is probably much shorter in
puddles.

(2) Duration of larval stage. — This depends on temperature and amount of food.
Under natural conditions it may probably be only three or four days, but under unfa-
vorable conditions (cold, overcrowding, absence of food) it may certainly extend to
weeks. 1 There are reasons for thinking that development is much hastened by
bright weather, in order to enable the imago to hatch out before desiccation of the
containing puddle.

(3) Food. — The larvae were frequently watched floating on the surface and feeding
on filaments of waterweed, amongst which they often entangle themselves. On dis-
section the intestine was found crammed with these filaments. It was observed that
in vitro the larvse scarcely grow in size unless they are given large quantities of water-
weed, which they dispose of very rapidly. On the other hand, larva: were often
caught in puddles in which no green vegetation could be seen. They may eat other
food, but it would seem as if waterweeds constitute their favorite diet. It was also
noted that they obtain shelter among these weeds from the current running through
the pools during or after rain.

(4) Enemies. — No observations could be made under this head, but we often found
many frogs and tadpoles in the breeding pools, apparently living at peace with the
larvse.

(5) Effects of desiccation.— Daring most of our stay in Freetown heavy showers fell
several times a day, so that the larvse could live secure from desiccation in all but
the most evanescent puddles. In September, however, there was a complete break
in the rains, lasting three days. A large number of the pools, even many of those
containing waterweed, and those fed by springs during rain, dried up completely.
The question whether the larvse had the power of living in the mud at the bottom of
the pools could now be tested by direct observation. The break in the rains was
followed by heavy showers, which immediately refilled all the puddles. Had the
larvse continued to exist in the mud, they would now have emerged again. As
regards the puddles in which the mud had completely dried, this was not the case.
No larvse at all were found in them for at least two days after the rain had refilled
them. After that interval larvse again appeared, but they were very small ones,
evidently just hatched from the egg. On the other hand, it was frequently
observed that if the mud did not become completely dry, the larvse would emerge
into active existence after another shower. These observations were supported by
some experiments in vitro , and we therefore conclude that the larvse can withstand
partial, though not complete, desiccation.2

(6) The same puddles constantly occupied. — We have suggested (paragraph 13) that
the position of the breeding pools may change according to the seasons, but while we
were in Freetown there was no change of season, and we generally found Anopheles
larvse in the same puddle, namely, in those which were suitable for them. Thus, of
two puddles lying close together, one would never contain larvse and the other
would always contain them. The explanation of this probably is that the larvse

1 One of us kept Culex larvse alive for two months in a bottle in the cold weather in
India.

2 One of us reared adults from full-grown larvse kept on damp blotting paper (in
India), but found that the young larvse died when kept under these conditions.

69

perish in the unsuitable pools, or that the adults generally return to the same pools
in order to lay their eggs. It seems likely that the adults generally lay their eggs in
the pools in which they themselves were bred, and that the insects thus learn by
experience the places most suitable for them.

(7) Detection. — It is easy to overlook Anopheles larvie unless they are searched for
in a bright light.

(8) Pupx. — The pupae of Anopheles seem to be smaller than those of the com-
moner species of Culex. They require about forty-eight hours to reach maturity in
vitro; perhaps less in natural conditions.

16. BIONOMICS OF ADULT ANOPHELES.

(1) Hoicking. — The adults generally hatch out in the evening; but their exit seems
often to depend on the meteorological conditions of the moment, and appears to be
delayed by rainy and windy weather.

(2) Food. — They can easily be kept alive in glass cages, test tubes, bottles, etc.
We kept some in this manner for a fortnight, and could doubtless have kept them
longer if we had wished to do so. We are able to confirm Bancroft’s statement (18)
that gnats feed on bananas; but they seem to prefer the fresh fruit. During the day
the insects remained at rest on the walls of the cage, but in the evening began to
fly about and to walk over the fruit, plunging their proboscis into it in many places,
so that the banana was sometimes covered with gnats, both male and female. They
also drink water frequently, and each can often be seen to be distended with the
fluid. Raw meat was offered to them, but they could not be observed to touch
it. Earth placed at the bottom of the cage seems to be suitable for them.

According to the accounts of the soldiers at Wilberforce, they bite almost entirely
in the evening and night, but have been known to feed on men during the day.
They can certainly be fed on men artificially during the daytime, simply by placing
them in test tubes and then applying the mouth of the tube to the skin. The stom-
ach can be observed to become distended in from one to two minutes or more; after
which the insect continues to suck, but commences to evacuate by the anus serum
containing a small percentage of red corpuscles. Culex voids only a clear fluid under
the same circumstances. The insects sometimes continue sucking like leeches for
five or ten minutes, voiding blood all the while; but at other times soon withdraw
the proboscis and then try another spot. It was noted, however, that Anopheles
fed in this manner, even after they had remained sucking for five or ten minutes,
never showed any great distension of the abdomen; while the contents of the stom-
ach still remained for some time transparent and red as seen through the scales of the
living insect. Moreover, in these cases the meal was generally digested or voided
within about twenty-four hours.

On the other hand, Anopheles which had fed themselves under natural conditions
generally presented a very different appearance. They were enormously distended;
while the contents of the stomach were thick, opaque, and black, and sometimes did
not disappear for three days. The only inference is that, under natural conditions,
the insects which can manage to do so gorge themselves over and over again during
the night — probably from the same subject.

(3) Propagation. — We also observed that while naturally fed gnats invariably laid
eggs after two or three days, those which had been bred from the larvie in captivity,
and had then been isolated and fed in test tubes, never did so, although Indore being
isolated they had long been in company with males. The inference is that fertiliza-
tion takes place only after the female has been fed.

We noted also that in a cage where many male and female gnats, Culex and Ano-
pheles, were kept together for weeks eggs were never laid, although the insects were
fed as described on bananas, and the cage contained water for them to lay their eggs
in. It seems, then, that a meal of blood is necessary before fertilization.

70

Lastly, we observed that previously fed and fertilized insects would lay a second
batch of eggs after a second meal of blood without a second fertilization, but never
laid a second batch of eggs without a second meal of blood. That is, one fertiliza-
tion suffices for several batches of eggs, but one meal of blood for only one batch of
eggs.

These observations are wholly in accord with the results of the prolonged study of
many kinds of gnats made in India by one of us; and it therefore seems likely that
the following law is likely to hold good for the Culicidie which feed on men, at least
for the commoner species.

Although these gnats can live indefinitely on fruit and perhaps juices of plants, the
female requires a meal of blood, both for fertilization and for the development of her
ova. In other words, the insects need blood for the propagation of their species.

Blood was never found in male Culiddx in Freetown, according with the general
law.

(4) Haunts. — The large majority of Anopheles caught by us in dwellings were
females which were generally much gorged, and, if fed at all, were invariably fertil-
ized; in other words, the males and unfed, or only slightly fed, females do not gen-
erally remain in the houses during the daytime, or if they did remain, kept in the
roofs or other dark places where they were little observed. On the whole, we think
that only those females which are so gorged that they can not fly far remain in the
houses during the day. We observed that if a cage full of Anopheles was disturbed
in the daytime, the insects always struggled toward the light as if to fly out from
the windows, and several which escaped from the cages actually did so. On one
occasion a large number escaped from their cage during the night in the rooms occu-
pied by one of us; none of them could be seen next morning.

Yet we may be quite sure that both the males and the unfed females haunt the
houses during the night. The invariably fertilized conditions of the gorged females
caught in the houses show that the males must be present in the houses when the
females feed, since the latter are often so much distended after feeding that they are
obviously unwilling to fly even a few feet from the bed of their victim; in other
words, fertilization must take place within the houses. The unfed females must, of
course, resort to human habitations during the night in order to obtain their food
at all.

These facts would seem to indicate that in Freetown in the rainy season the
Anopheles resort to the houses during the night, but that all except the gorged females
live elsewhere during the daytime — possibly sleep in the trees and shrubs. The
point is of interest as tending to show that large numbers of Anopheles may be present
in a dwelling during the night, without it being easy to find them during the day.

It should, however, be added that in India males and unfed females were often
found in the houses in large numbers by one of us. Possibly different species have
different habits in this respect.

Several old residents of the country informed us that gnats are usually very preva-
lent in the presence of much vegetation- — especially long grass and undergrowth.
Though it is difficult to see how such can favor the lame, we can understand that
much vegetation can shelter the adults of certain species, which may even feed on
particular kinds of plants when they can not obtain blood, and may consequently
find it easier to live where these plants afford them both food and shelter than else-
where. It must also be remembered that gnats can certainly bite birds and other
mammalia besides man; and that such are apt to congregate where there is much
vegetation. On the whole, then, there is nothing improbable in the idea that the
Freetown Anopheles should live outside the houses in the daytime.

O

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