INTRODUCTION.
These flies get the common name of sand flies from their being a major pest in
coastal areas, that of no-see-ums from the fact that most people do not see them because
of their small size, and that of biting midges because of the strong resemblance of some
species to midges. These are a pest because of the severe or painful bites they inflict,
and they are vectors of disease in livestock. Although found throughout the United States
and Canada, they are concentrated along coastal areas and waterways.
RECOGNITION.
Adults usually about 1132-118" (1-3 mm; range 1-6 mm) long; slender to
moderately robust. Color generally dark, wings sometimes with dark areas. Head with ocelli
lacking, eyes touching to widely separated; female with biting and sucking mouthparts.
Antennae usually 15-segmented (range 13-15), mate's plumose or featherlik,e. Front tarsi
not lengthened. Wing with thickened part of coastal vein (C; on front edge) usually ending
1/2-3/4 way to wing tip, radial veins (R) prominent, medial vein (M) 2-branched, and wings
held flat over body at rest.
SIMILAR GROUPS.
Midges (Chironomidae) with thickened part of coastal vein (C) ending
near wing tip, medial vein (M) unbranched, front tarsi usually lengthened and wings held
rooflike over body at rest.
Mosquitoes (Culicidae) with scales along veins and wing margin.
Black flies (Simuliidae) with robust, humpbacked body, antennae
short, bare, beadlike segments, and usually 1 1 -segmented (range 9-12).
REPRESENTATIVE SPECIES.
- Bodega black gnat, Leptoconops kerteszi Kieffer. Length about 1/16-1/8" (2-3 mm);
color black except legs paler towards tarsi and wings white; antenna 15-sagmented in male,
13-sagmented in female; found in western North America, with adults active from early
March to early October in California.
- Salt marsh punkie, Cuticoides furens (Posy). Length about 1/16" (2-2.5 mm); color
dark with white markings on thorax, wings dark with transparent areas; antenna 15-
segmented; found in all Atlantic (Massachusetts southward) and Gulf coastal states in the
U.S., with adults active from June into August in New York state.
- Valley black gnat, Leptoconops torrens Townsend. Length about 1/16" (2 mm); color
black except legs paler towards tarsi and wings white; antenna 15-segmented in male,
14-segmented in female; found in western U.S., with adults active from mid-May to late
June.
BIOLOGY.
Eggs are laid in batches varying from 30-40 up to 450. Larvae of Leptoconops
burrow in soil, primarily in and areas and on coastal and inland beaches. In some species,
they enter diapause as the soil dries out and resume development when the seasonal rains
come. Larvae of Culicoides vary in habit from burrowing in moist soil to being fully
aquatic and free-swimming. There are 4 larval instars which may require from 3 weeks to 2
years or more in species inhabiting and areas and in some arctic species. The pupal stage
is of short duration. Adults of many species assemble in swarms where mating takes place;
the male's plumose antennae is an auditory organ which detects the wing beat tone of the
female. Females typically require a blood meal before egg laying. Both sexes may visit
flowers for nectar. Adults usually live only a few days.
Fortunately in the U.S., sand flies are not known to be disease vectors
to humans. However, Cuticoides spp. are vectors of blue tongue virus in sheep and cattle
and epizootic hasmorrhagic disease in the Virginian white-tailed deer, Odocoileus
virginianus (Zimmermann).
HABITS.
Adults typically live in moist areas around the larval habitat. Some species are
characteristically found in coastal salt marshes, in inland saline swamps and marshy
areas, in heavily fertilized areas frequented by livestock, in cactus, in desert areas,
etc.
The density of some species will be reduced to 1/10th at 230 ft (70 m)
out from their breeding site. Some species can be blown downwind over 3,281 ft (1,000 m)
with no decrease in density indicating that their population density may be more a
function of host availability than the distance from the breeding site.
In the more temperate/northern areas, adult sand fly activity begins in
the early spring and subsides by late June. The more tropical the area, the longer the
adult activity persists to being virtually year round in southern Florida, Texas, and
California. Most species of sand flies are crepuscular, active at dusk/sunset. However,
most species of Leptoconops are diurnal (active at sunrise and sunset) but some are active
in the daytime, while other species are nocturnal.
Both sexes commonly feed on nectar but some males do not feed. Females
of most species require a blood meal for egg development. Species of Culicoides,
Leptoconops, and some Forcipomyia are bloodsuckers of vertebrates, primarily mammals and
birds. Others feed on the blood/haemolymph of large insects such as moths, dragonflies,
mayflies, etc.
The mouthparts are somewhat crude compared to mosquitoes. They use a
sawlike motion to gain entry through the skin which typically causes a sharp pain and
leaves a bright red dot where hemorrhaging has occurred, with a subsequent surrounding
inflamed reddish area. Itching can be intense and usually lasts for several days. The
intensity of their bite is far far out of proportion to their size and they can be very
voracious and persistent feeders.
Many species of adult sand flies assemble in swarms for mating
purposes. Such swarms maintain a to-and-fro dancing flight above a landmark such as a bush
or pond margin. A few species mate on a substrate, such as the ground, without a swarming
flight.
