Coping with Sand Flies in the Virgin Islands


 By W. I. Knausenberger
 Pest Management Specialist
 C.V.I. Cooperative Extension Service


 Virgin Islands residents hardly need an introduction to their
tiniest airborne assailants -- the sand flies, biting flies "of the
smallest kind," one-sixteenth of an inch long, dark gray to black
in color, with spotted wings, and packing a mighty bite! Locally,
they are referred to also as "mampi" or "no-see-ums," but they
also have been called "flying teeth," "living ashes," punkiess,"
and many other names -- some unprintable -- all over the world.
This article will outline the nature of the sand fly problem and
then will recommend some coping strategies.


Visitors to the Caribbean area are especially sensitive to the bites of
the unpopular sand fly. This young woman ata local beach displays
the sizable welts which resulted from sand fly bites.

 In the Virgin Islands, people who spend time outdoors are
especially likely to be bothered by sand flies for several reasons.
First, sand flies are active at dawn and dusk (and at night), seldom
biting later than three hours after sunrise, and seldom earlier
in the evening than two hours before sunset -- just the time a
gardener is likely to be out. Some annoyance may be experienced
on calm days, especially when the sky is overcast and the air is
humid following a light rain. In areas of high infestation, bites may
be experienced at any time, especially in shaded areas. Also, Virgin
Islands gardens are generally located in sites relatively close to
favorable sand fly breeding places such as wet mud around ponds,
along streams, in saltmarshes, and mangrove swamps with exposed
mud flats. The highest production of sand flies can occur from the
pond habitat -- 20 flies per square foot every day. The fluctuating
water levels of the Virgin Island impoundments are especially


favorable most sand flies start to emerge beginning one week
after heavy rains start, until the water level drops below the average
level. This situation probably accounts for the greater number of
flies during periods of high rainfall -- especially April to June, and
in the autumn months. Nevertheless, in the warm climate of our
area, emergence of this sand fly is likely to remain at a high level
all year. The only factors which reduce the rate of emergence
are long periods of flooding or drying of the immature insects'
breeding substance. A single generation requires three to six
weeks to develop, but there are always stages "ready to go."

 Not only are breeding places common and widespread, but
the sand flies are particularly likely to occur 2-3 miles or more
downwind from these places. Prevailing winds in the Virgin Islands
are basically from the East and Northeast, so most of the major
ponds and marshes are upwind from concentrations of people in
the Virgin Islands. Whenever the wind is blowing 5-6 mph, biting
activity ceases, but the annoyance may well continue in protected
areas. Ironically, the very people who work hardest physically are
most likely to be severely annoyed by sand flies. This is because
the physiological factors which attract these flies namely, a com-
bination of high skin temperature, moisture, carbon dioxide (in
the breath), and odors of chemicals associated with perspiration
and breathing -- are produced in generous amounts during physical
activity. It's the female sand fly that "bites" to obtain a meal of
blood, necessary for her eggs to develop. The same applies to
mosquitos! To add insult to injury, even our homes are not secure;
sand flies are unique among biting insects in being able to pass
through mosquito-proof window screening, further menacing the
person seeking refuge indoors. Also, they are attracted to light.

 Despite the common name (which perpetuates a popular
misconception), "sand flies" only rarely breed in the sand. Of the
25 species (kinds) of sand flies in the Caribbean area, only three
can be found breeding in sand on beaches, and then only under
very special conditions. Of these three, none is present in the
U.S. Virgin Islands. Of the six species which are found here, five
have been recorded on St. Croix, three on St. John and two on
St. Thomas. The single most important species, however, Culi-
coides furens, is found abundantly on all three islands. Fortun-
ately, we don't have to worry much about the other species, which
breed in an even greater variety of places, such as wet tree holes,
crab holes, and damp rotting plant material. Interested readers
can find more details on the sand fly life cycle by referring to p. 57
of the 9th Annual Agriculture and Food Fair booklet.

 Control of sand flies is a responsibility too large for individu-
als to hope to achieve because of the sheer physical difficulty of
locating and dealing with all breeding places and the adult flies
coming from them. Because of the individuality of each problem,
the choice of the most appropriate control measures requires
considerable investigation. Such investigations have been initiated
by the College of the Virgin Islands' Cooperative Extension Ser-
vice.

 This program seeks to combine planning and monitoring with
physical control measures; judicious use of new and better selective
insecticides on carefully selected breeding sites; adult resting sites
and flight paths; biological control (use of natural enemies); and
personal protection measures. Such a total control effort requires
the coordinated efforts of the entire affected community. In any
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