70 ANMAL IM'I'OKIS OF I >i:P.\ IMM I iX T OF AGRICULTURE. 1937 
111 co(jiK>rati<)ii with the r.urcau of HioloKical Survoy. the Civilian Conserva- 
tion Corps, and the State aj^cncics concerned in niosqiiit^) control in Maryland, 
New Jersey, and Delaware, work was hej^iin to assist the C. C C. camps to 
carry out more elTcK-tively the mosquito-control projects to which they were 
assijjned in these States. 
Survey.s were made to determine the more important mo.sfpiito-hreedins: areas. 
Advice was al.so given as to the most practical procedure to he followed in 
abatinj; the moscjuito plajrue in different areas. Intensive surveys of the fauna 
and llora of the marshes are heinj; made to determine the relationship between 
mos(niito-control operations and the disturbance of wildlife on tidal marshes, 
and to w(>igh the probable inliuence of different types of control on the.se forms 
of life. The.se surveys are not yet complete l)ut present data indicate that 
with a knowledge of the .soil types, water levels, and other factors, the time 
and expense of ditching marshland may be kept at a minimum, the mo.squito 
control made more effective, and wildlife disturbed but little. If there is no 
great change in the .salinity of the water passing into them, marshes which 
have a compact soil, are Hooded by lunar tides, and have a fairly good tide range 
in the ditches will maintain their original vegetation in good condition. On 
the other hand, marshes which have a porous soil on which water has been 
practically impounded over long periods will show marked changes if the 
surface water is removed and the water table permanently lowered. 
SAND FLIES 
For relief from the annoyance of sand flies in houses it has been found that 
a mixture of 1 part of commercial pyrethrum extract and 20 parts of very 
light lubricating oil applied to the window and door screens gives good pro- 
tection for a considerable length of time to persons inside the hou.ses. 
SURGICAL MAGGOTS 
Following the di.scovery of the value of urea as a healing agent, consider- 
able work of a service nature has been performed by the Bureau in supplying 
information to both doctors and laity as to where urea could be purchased and 
the methods of its application. Much work of the same nature is still riMiuired 
on the subject of allantoiu, another compound found in maggot secretions. 
The search for healing agents present in maggot excretions was continued 
during the year. Two substances, ammonium carbonate and amm(»nium bicar- 
honate. which occur in the excretions were given preliminary tests, but in gen- 
<?ral the results obtained with them did not appear to be distinctly benehcial. 
^ind the experiments were discontinued. 
In studies of the anatomy and physiology of blowfly maggots to determine 
how these organisms produce their healing or beneficial effects, considerable 
improvement has been made in research technique. A vital dye, alizarin, has 
been u.sed with much success in determining the hydrogen-ion concentration of 
various parts of the alimentary canal. It is given with the food of the larvae, 
and when eaten it stains various parts of the digestive tract a characteristic 
red or yellow. This same dye is being used to determine calcium metabolism 
of the fly maggots. 
FIRE ANTS 
Numerous tests of methods to control fire ants f S'r)/r;;o/>.v/.s si»p.). which are 
so destructive to young quail and otherwise injurious in the Southeastern 
States, have shown that api)roximately ."iO i)ercent (»f the lire ant colonies can 
be destroyed by applying a solution of sodium cyanide C(»ntainiug 1 ounce 
of the chemical to a gallon of water. Ai)plications of move than 1 ouium^ (^f 
sodium cyanide per gallon of water increase the efliciiMU-y of the method in 
sandy .soils, but 1 ounce of the dry cyanide pla<'ed .'» to inch(>s deep apiH\»rs 
to be more efllcient than the li(iuid mat«M-ial on clay soils, although loss 
eflicient on .sandy .soils. l?etter kills are obtained if the liquid cy.inide solution 
Is poured down the galleri(»s rather than into holes punched into the ground 
around the colony. (Jreater kills may be e\])ected if the C(>lonies are treated 
as early as March :ind .\i)ril rather than in May. .Tune, or .Inly, an«l a greater 
percentage of the colonies \\(>r«» d(»slroyed when th(^ niatiuials W(M-e applied in 
wet weather than under dry conditions. 
Tests with carbon disuljiliidc. both as a liquid and as :ni tMuulsion. and 
chloropicrin indicated lliat Ihcy were s.-it isf.actory materials for di'^troying 
the colonies. 
