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The
Egg
Mating
of hard ticks usually occurs while they are on the host animal. Afterwards
the female drops to the ground and, after a brief pre-oviposition period
of three to 10 days, begins to deposit eggs on or near the earth. The
female hard tick feeds once, lays one large batch of eggs sometimes
numbering in the thousands, and dies. Most of the soft ticks engorge
with blood several times and deposit about 20 to 50 eggs in a batch
after each blood meal. Eggs hatch in two weeks to several months, depending
upon temperature, humidity and other environmental factors.
The
Larva
The larvae,
or "seed ticks," have only six legs, and the sexes are indistinguishable.
Their chances of attaching to a host are precarious, sometimes resulting
in prolonged fasts.
Despite tolerance
to starvation, a very high percentage die. Some individuals climb on
vegetation, waiting for a small rodent to pass within reach. Some actively
seek a vertebrate host, being guided by the sent of the animal. After
a blood meal, the engorged larvae usually drop to the soil and molt
to the eight-legged nymph stage. The larvae of one-host ticks remain
on the host to molt.
The
Nymph
The
nymph has eight legs like the adult but has no genital opening. This
stage also must undergo a critical waiting period for a suitable host.
After engorgement, the nymph drops from the host, molts, and becomes
an adult. Nymphs may rest for long periods before becoming adults. Some
species of hard ticks live less than one year while others live three
yearsor more. Each time a tick leaves its host it risks its survival
on on finding another host. Some species have the advantage of molting
on the host. For example, the cattle tick is a one-host tick. Multiple-host
tick species are able to exist because of their great reproductive capacity
and their ability to survive for a long time without food.
Hard ticks have
only one nymphal instar, the nymph becoming an adult after molting.
Soft ticks may have several nymphal instars.
The
Adult
Typically,
the nymph molts after engorgement and becomes an adult. Sex then is
distinguishable for the first time as the female hard tick differs from
the male in having a small scutum. The sex of soft ticks may be determined
by the shape of the genital opening located between the second pair
of legs. In male soft ticks the genital opening is almost circular,
while it is oval and definitely broader than long in female specimens.
Unlike mosquitoes, both male and female hard ticks are blood suckers,
and both require several days feeding before copulation. After the male
hard tick becomes engorged, he usually copulates with one or more females
and then dies. Following copulation, the female tick drops to the ground.
The eggs require several days to develop. Then she begins oviposition.
After a few more days, her life's mission accomplished, the spent female
hard tick also dies. The female soft tick may lay several small batches
of eggs but she requires another blood meal before each episode of oviposition.
For more information, contact your local health department,
or the Texas Department of State Health Services.
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