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A NEW MOSQUITO CAGE. 

Marshall Langton Price. 

Baltimore, Maryland, U. S. A. 

The mosquito problem is becoming an important one throughout 
practically all of the western hemisphere, as well as in large areas of 
Europe, Asia, Africa, and Australia. I do not refer alone to that 
portion of North America lying between the thirtieth parallels of 
north and south latitudes. In these regions the normal habitat of 
the Stegomyia jasciata, endemic and epidemic foci of yellow fever 
make the problem not only important, but urgent; in fact, a large 
part of the energies of sanitary administrations in Cuba, Mexico, and 
the Gulf states of the United States, must be directed toward the 
destruction of mosquitoes and the prevention of their breeding. 
There are evidences, however, that this problem, now mainly the 
problem of the hygienist of the Stegomyia area, must be met also by 
the hygienists of all areas where diptera normally or occasionally 
occur. Mosquitoes are now entering public hygiene in the United 
States, not alone in the relatively insignificant "malaria area," in 
the r61e of "unsanitary nuisances." 

Although all varieties of the common Culex and Anopheles have 
been proven to convey disease, the people of Northern American lati- 
tudes are more directly interested in the problem from the standpoint 
of public comfort. In certain areas, notably on the Atlantic coast of 
New Jersey and New York, the mosquito is an important economic 
problem, and its extermination in these states has repaid many fold 
the expenditure of pubUc money through increased value of the land. 
The extermination of mosquitoes over any large area, or upon any 
extensive scale, requires careful study and a definite plan of cam- 
paign. An absolutely essential preUminary, is a geographical survey 
of the area involved, to determine the varieties of mosquitoes to be 
dealt with, and their distribution. In fact the sanitary laboratory 
in the near future will have to make studies of variety and distribu- 
tion of mosquitoes with the same care and attention as is now given 
to pathogenic organisms. For this purpose it is necessary to collect, 

123 



124 Marshall Langton Price 

raise, and observe mosquitoes in the laboratory. The study of 
mosquitoes includes the collection of eggs or larvae, hatching in water, 
and the preservation and observation of the imagines in suitable 
cages. The cage here described was devised with the object of 
facilitating the raising of mosquitoes and their observation during 
hatching, and in the imago stage. As a preUminary to experiment, 
observation, and diagnosis of variety, eggs or larvae must be collected, 
and transferred to hatching-jars. The larvae may be collected by 
means of a fine net passed through any pond which may breed mos- 
quitoes, well below the surface of the water. Eggs may be easily 
recognized by a careful observer, and transferred by means of a 
spoon. The eggs or larvae are transferred to a hatching-jar filled 
with rainwater until they have fully developed. 

The usual method of developing imagines is to hatch the eggs or 
larvae in jars protected with netting, and to transfer each adult insect 
separately by means of a short test-tube to cages of wire netting. In 
order to avoid the laborious handling of each single insect, to avoid 
loss during transfer, and to facilitate observation and experiment, 
the larvae jars have been combined with the imago cage in the manner 
illustrated in the drawing. 

Description oj the cage. — The cage is of wood, divided into three compartments by 
partitions. The base is made of a single piece of wood and supports the two vertical 
wooden partitions and two end pieces. A floor separates the larvae jars from the 
imago compartments. The top of each imago compartment is closed by a piece of 
plate glass, held lightly by screws. The sides of the imago portion of the cage are 
closed by wire and cloth netting (a double layer) held in place by brass upholstery tacks. 

The two vertical partitions divide the space between the base and floor into three 
compartments, each made to fit accurately one of the larvae jars, so that the latter can be 
slid easily in and out of their compartments without allowing any interval through 
which the insects can escape when the jar is in place. Each larvae jar communicates 
with its imago compartment by an opening slightly smaller than the mouth of the jar. 
Through this opening the imagines pass upward into the netting cage as soon as they 
undergo their metamorphosis. 

The partitions and ends of the cage are supported above by two longitudinal 
wooden strips each ij" wide, mortised into the partitions and ends. All of the wood 
used in the construction of the cage is J" pine. 

As it is important for the larvae jars to fit accurately, the wood should be well 
seasoned and given a thorough rubbing with an oil filler. 

The cage, including the netting, should be painted inside and out with a white 
enamel paint, which will add materially in observing the mosquitoes. 

The plates inclosing the tops of each compartment are a good quality of plate 
glass, J" thick, and bored for from three to six o . 2" screws. 



A New Mosquito Cage 



125 



The two end plates are qH" by &■?/'■ The plate closing the central compart- 
ment is 9^V' by 8)^", and the feeding plate of the same dimensions. 

The full size of the cage is, height i8 inches, width 8 inches, length 28 inches. The 
larvae jars are 2J" high, and the diameter of their mouths 4i". Their compartments 
correspond in height, but are somewhat larger in the other dimensions. A space 
is thus allowed on the floor of the imago compartment upon which the mosquitoes can 
rest, and upon which their food (dates, bananas, sugar, and water, etc.) is placed in 
small butter plates. 

Feeding-plate. — If it is desired to propagate mosquitoes through 
several generations, or to persuade fecund females to lay, or to carry 



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7 



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Fig. I. 

out any line of experiments in diseases for which the mosquito is the 
intermediate host, provision must be made to furnish the impregnated 
female insects with blood. This is absolutely essential in the case of 
the Stegomyia, as the female will not lay fertile eggs (if at all) without 
the previous ingestion of blood, preferably from a human source. 

The usual method of furnishing blood to insects in cages, is to pro- 
vide a special sleeve of netting, protected with a draw-string through 
which the arm can be introduced into the cage. There are two serious 
objections to this method. One is that the string produces folds in 
the netting into which mosquitoes will frequently squeeze themselves 



126 Marshall Langton Price 

and die, and the other is the impossibility of observing the insects 
during the act of sucking blood. In the present cage the netting 
sleeve is replaced by a feeding-plate. This plate is of glass with a 
central elliptical opening made to fit the forearm of the experimenter 
at its largest part. A paper or cardboard pattern should be made 
for the feeding-plate and for the three plates closing the top of the 
compartments, to show their size, the position of the screw holes, and 
the position of the central opening in the feeding-plate. 

To make the pattern for the feeding-plate, a piece of paper or strathmore board 
should be cut to the exact size of the plate and the center marked by means of two 
diagonals. The major and minor axes of the forearm should be determined by means 
of a pair of compasses or calipers. Draw the major and minor axes intersecting the 
center at right angles to the sides and with two pins attached to a piece of string, the 
length of the major axis, draw the ellipse. The pins should be placed equidistant 
from the center, at such a distance that the curve will just intersect the ends of the axes. 

The feeding-plate now in use in the cage was bored and cut to fit the pattern of 
the forearm by a Baltimore firm dealing in plate glass, but it could probably be made 
more economically by etching with hydrofluoric acid. In this case it could easily be 
made an exact fit of the forearm of the experimenter. In this case the ellipse could 
be described as already stated. After taking the axes of the forearm and describing 
the ellipse, the forearm may be measured with a piece of lead tape, drawn over the 
ellipse, and the pattern cut out on a piece of paraffined paper. By pouring hydro- 
fluoric acid upon the opening in the paper and using if necessary several pieces of paper, 
a hole can' be etched which will fit accurately the arm from which the pattern was 
made. 

Method of using the feeding-plate. — The feeding-plate may be 
used, when it is necessary to supply the impregnated females with 
blood, in the following manner. This involves the substitution of the 
feeding-plate for the plain glass plate closing the top of the compart- 
ment. To do this the screws are removed from the top plate and the 
feeding-plate placed against its edge and gradually pressed against 
the top plate until it has replaced the latter, sliding off at the same 
time the top plate. The opening in the feeding-plate is closed during 
this manipulation by one of the covers ground to fit the top of the 
larvae jars. When the feeding-plate is in situ and lightly fastened 
with screws, the cover is removed, and the forearm inserted. If the 
opening does not fit accurately a piece of gauze is wrapped around 
the forearm below the elbow. This glass plate allows an uninterrupted 
view of the females during blood-sucking. 

The cost of the cage with the glass plates is about $15. The largest part of the 
cost is in the glass plates, but the increased facility of observation more than compen- 



A New Mosquito Cage 127 

sates for their cost. These plates cose in Baltimore $i . 50 each for the plain plate-glass 
top plates, and $5 for the feeding-plate. The cost of the latter is mainly in the feeding- 
opening, as the boring and cutting of these plates is a difficult and delicate operation. 
The larvae jars are the cylindrical jars with ground covers used for instruments 
and dressings, and cost 50 cents each. Their size is 2 J" by 4^". The wooden founda- 
tion may be made by any intelligent carpenter. This portion of the cage cost $2 .50. 
The netting can be applied in half an hour by anyone. An inner layer of fine mesh- 
cloth netting and an outer layer of wire netting were used in this cage. 

The glass feeding-plate will be found especially valuable in remov- 
ing adult insects from the cage, as it permits binoptric vision, v^hich is 
very difficult if netting or a gauze sleeve is used. There being no 
netting in the top of the cage, a full and unobstructed view of the 
imagines is always available. The combination of the larvae jars 
with the imago cage reheves the experimenter from any close care and 
observation other than the maintenance of a proper temperature and 
the supplying of the imagines with food and blood when necessary. 

The larvae jars may be removed from the cage at all times, except- 
ing when the pupae are undergoing metamorphosis. By placing the 
jars upon a white or neutral surface, nearly all the details of structure 
necessary for diagnosis may be observed without magnification. 

The total weight of the cage, including water in the jars, is less 
than ten pounds, and it can be easily moved about for observation 
and demonstration. 

With the cage made in three compartments, as in the experiments 
for which it was devised, two separate methods of treatment and one 
control were provided for, but any number of compartments can be 
constructed, or a unit plan may be employed.