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ARACHNIDA KEY (Scorpions,
Spiders & Mites) (Contact) Please CLICK on underlined links
to navigate within the key or on photos to enlarge: Search for Subjects with Ctrl/F [Also See: <Arachnida Details>] The following key aids in
separating the more common orders of Arachnida followed by details on the
Acarina. Although the taxonomy of
Arachnida is regularly being updated the present organization is simplified
for the identification of medically important groups. Some useful diagnostic
characteristics may be viewed at the following: <Argasidae>, <capitulum>, <Dermacentor andersoni>, <Dermacentor variabilis>, <Dermanyssus gallinae>, <Dermanyssus sanguineus>, <Entrombicula alfreddugesii>, <Eutrombicula batatas>, <Haemaphysalis
leporis-palustris>,
<Liponyssus bascoti>, <Pediculoides ventricosus>, <Psoroptes communis>, <Rhipicephalus sanguineus>, <Sarcoptes scabiei>, <Tunga penetrans> Principal Groups Included: Acarina, Antricola,
Argasidae,
Argus, Dermacentor, Dermanyssidae,
Ixodidae,
Ixodoidea, Ornithodoros, Otobius, Parasitoidea, Sarcoptidae, Sarcoptoidea, Trombidiidae, Trombidoidea - - - - - - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - - - |
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1. The abdomen is clearly
segmented _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 Abdomen
segments are not clearly visible _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4 2. The abdomen bears a
tailed extension (Scorpions) Expand_ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ Scorpiones ( = old Scorpionida)
Abdomen does
not have such an extension _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
3 3. Palps are chelated or
have pincers (claws) (Pseudoscorpions)
Expand _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Pseudoscorpionida
.Palps are not chelated
or lacking claws resembling pincers.
There is a long tail, large palps and small chelicerae Expand_ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Pedipalpida 4. The abdomen is joined to
the cephalothorax by a short, narrow stalk (Spiders) Expand _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Araneida
The
abdomen is fused with the cephalothorax to form a saclike body (Mites) Expand _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ Acarina
= = = = = = = = = = =
= = = = = = = = = Order: ACARINA (Mites) There
are usually eight suborders of Acarina recognized with their respiratory
system structure serving to distinguish them. Five suborders have species with parasitic habits that can
cause medical problems directly or indirectly by transmitting pathogens to humans
and animals. 1. The body is worm-like,
being extended posteriorily. They are
clearly ringed and have rudimentary legs with only 3 segments. They are
parasitic in sebaceous glands or hair folicles of mammals (Suborder Brachypoda
and only one superfamily)_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ Demodicoidea Body is not
worm-like and not extended posteriorily.
They are not parasitic in sebaceous glands or hair follicles of
mammals _ _ 2 2. Tracheae are present with
two spiracular openings (one on each body side generally above the 3rd or 4th
coxa or somewhat behind
them. Spiracles open through
distinct stigmatal plates _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Suborder Mesostigmata 2b. The hypostome is large and equipped
underneath with many recurved teeth;
the venter has furrows and the skin is leathery.
These are larger species
(Ticks) _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Superfamily Ixodoidea 2c. The hypostome is small and lacks recurved
teeth underneath; the venter does not have furrows but frequently coriacous
shields. _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ Superfamily
Parasitoidea When
tracheae are present they do not open through lateral spiracles _ _ _ _ _ _ _
_ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 3. Tracheae are usually
present with the spiracular openings close to or at the bases of the
chelicerae. Larvae are often
parasitic and the
adults are free-living _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Suborder Prostigmata 3b. The last segment of palpus does not form a
"thumb" to preceding joint.
The body has few hairs _
Superfamily Eupodoidea 3c. The last segment of palpus forms a
"thumb" to the preceding joint that terminates in a claw _ Superfamily Trombidoidea Tracheae
when present do not open at the bases of the chelicerae _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4 4. Tracheae are present and
the body is divided into a cephalothorax and abdomen. The abdomen reveals segmentation. Females have
aclavate hair between the 1st and 2nd pair of legs __ _ Suborder Heterostigmata (There is only one Superfamily: _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Tarsonemoidea) Tracheae are
absent and there is no division between the cephalothorax and abdomen. The abdomen does not show true
segmentation. Females never
have a clavate hair between the 1st and 2nd pair of legs. _ _ _ _
_ _ _ _ _ _Suborder: Astigmata 4b. The body surface has
fine parallel lines or folds. The
tarsi frequently have stalked suckers.
They are parasitic in all stages and
mainly on vertebrates. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ Superfamily: Sarcoptoidea 4c. The body surface does not have fine
parallel lines. The tarsi are without
stalked suckers and adults are never true parasites. _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _
Superfamily: Tyroglyphoidea Superfamily: IXODOIDEA 1. A scutum is absent. The capitulum is ventral
and usually hidden underneath the anterior margin and subterminal. The
appearance of both sexes is identical (Fig. 1) _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Argasidae 2. Scutum is present. In males it extends over the entire dorsal
surface, while in females, nymphs and larvae only on part of the
anterior dorsal surface. The
capitulum is terminal and visible from the dorsal surface (Fig. 2) _ _ _ _ _ _ _ _ _ _ _ _ Ixodidae Family: ARGASIDAE Argasidae includes ticks that
do not have a scutum and are referred to as "Soft Ticks." Sexual dimorphism is minimal and males
closely resemble females. The
capitulum is always inferior and the spiracles are small and situated
anteriorily to coxa #4. The adult
ingegument is leathery, wrinkled and granulated or contain tubercles. Palps are free and all segments are
movable. Porose areas are
absent. The size of adults never
increases much after feeding, but then fasting they resmble bedbugs by their
flattened appearance. The main hosts
are birds, domestic animals, rodents, bats and humans. They are mostly nocturnal when
feeding. Four main genera are Argas, Ornithodoros,
Antricola and Otobius. 1. Body margin thin and
acute. A suture separates the dorsal
and ventral surfaces (Fig. 3) _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ Genus: Argas Body
margin not thin and acute, however if thus then there is no suture separating
the dorsal and ventral surfaces (Fig. 1) _ _ _
2 2. The integument of nymphs
is replete with spines. The hypostome
is well developed. Adults have a
granular integument and the
hypostome is vestigial _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ Genus: Otobius
Integument of nymphs is without many spines but rather with
tubercules. The hypostome is not
vestigial in nymphs and adults _ 3 3. The hypostome is shaped
like a scoop on the dorsal surface, but broad at the base (Bat
parasites) _ _ _ _ _ _ _ Genus: Antricola The
hypostome is not shaped like a scoop on the dorsum, and it is not as broad at
its base _ _ _ _ _ _ _ _ _ Genus: Ornithodoros Genus: ARGAS There are not many species in the
genus Argus, but some are
cosmopolitan. The most common species
are as follows: 1. The body is almost
circular or discoidal _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Argas vespertilionis Latr. The body
is not circular, but longer than wide _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _2 2. Body margins are
striated _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ 3 Body
margins are not striated but outlined by quadrangular cell-like plates (Fig. 3)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Argas
persicus Oken 3. The body is somewhat
conical-shaped anteriorly. The dorsum
is marked with polygonal depressed areas.
A large species (15 X 10 mm)
(Present in Eastern Africa) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ Argas brumpti Neum. Body is
round anteriorly. The dorsum has fine
wrinkles and discs (as in Argus persicus but
not as large). (Present in Europe, North Africa and
America). _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ Argas
reflexus Fahr. Genus: ORNITHODOROS Many medically important
species in the genus Ornithodoros attack
humans and vector severe diseases.
Only a few species are cosmopolitan in distribution and the taxonomy
is under periodic revision. 1. There are flaps or cheeks
at the sides of the camerostome _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 Flaps are
absent _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ 5 2. The tarsi have humps
that sometimes are quite small (Fig. 4) (Brazilian species) _ _ _
_ _ _ Ornithodoros brasiliensis
Aragao Tarsi do
not have humps _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ 3 3. Tarsus #4 has a long sub
apical extension _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ Ornithodoros tholozani (Labott &
Megn.) Tarsus #4
does not have such an extension _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ 4 4. Discs are large and
conspicuous (occur from southern North America to Argentina) (Fig. 1) _ Ornithodoros talaje Guerin-Men. Discs are
quite small and inconspicuous (occur in Central & northern South America)
_ _ _ _ _ _ _ _Ornithodoros
rudis Karsch 5. The integument is
lightly wrinkled. The dorsum has two
parallel and elongated discs near the front (occur from North Africa to
Iran) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _Ornithodoros lahorensis Neum. Integument
is strongly wrinkled. Discs are
either present or absent but not in the above described shape._ _ _ _ _ _ _ _
_ _ _ 6 6. Eyes are present _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ 7 Eyes are
absent _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 8 7. The anterior eyes are
much larger than the posterior ones (occur on Pacific coast from California
to Mexico _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Ornithodoros coriaceus Koch Both
anterior and posterior eyes are about the same size (occur from North Africa
to India)_ _ _ Ornithodoros savignyi Aud. 8. Humps are present and
prominent on the dorsum of all tarsi
(Fig. 4)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 9 Humps
when present do not occur on all the tarsi _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 10 9. Tarsus #4 has three
humps (occur in desert areas of North Africa) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Ornithodoros
moubata Murray Tarsus #4
has only one apical hump, which may appear as an apical extension (occur in
southern South America) _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _Ornithodoros rostratus Aragao 10. Tarsi are bifurcated and
possess dorsal humps (occur in North Africa) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Ornithodoros foleyi Parrot Tarsi
are not bifurcated and do not have on all or some tarsi _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 11 11. There are no humps on
the dorsum of all tarsi (occur in western North America) (Fig. 1) _ _ _ Ornithodoros hermsi Wheeler,
Herms
& Meyer Some
tarsi possess humps on their dorsum _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 12 12. Tarsal dorsal humps are
very long. Tarsus #4 has a subapical
extension. The mammillae are very
large and coarse (occur in
southern South America _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Ornithodoros rostratus Aragao Tarsal
numps are not as long and mammillae are not as large and coarse _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
13 13. Tarsus #4 is without
humps but with a subapical extension (occur in Mexico) _ _ _ _ _ _ _ _ _ Ornithodoros nicollei Mooser Tarsus
#4 has neither humps nor subapical extensions _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 14 14. Mammilliae are large (Fig. 1),
but scarce and not crowded (occur in southern North America) _ Ornithodoros
turicata Duges
Mammillae are small (Fig. 1), numerous and crowded
(occur in western North America) _ _
_ _ _Ornithodoros parkeri Cooley There are only two species of Otobius in North America (O. megnini
= spinose ear tick and O. lagophilus
Cooley & Kohls). Both of these species
have distinctive spinose integuments.
The genus Antricola
of America attacks bats and not humans. Family: IXODIDAE The Ixodidae include
those ticks, which have a scutum or shield and have been referred to as
"hard ticks." There is no
marked sexual dimorphism with males being covered on the dorsum by the scutum
and not able to distend themselves.
Females can become enlarged when engorged and the scutum is a small
shield behind the capitulum. The capitulum
is terminal and in females there are porose areas present. The family includes the majority of ticks
and is cosmopolitan. The principal
hosts are mammals, reptiles, amphibians and birds. Some of the more important genera are noted in the following
key: 1. There is an anal groove,
which surrounds the front part of the anus (Fig. 5). Eyes are absent (Cosmopolitan) _ _ Ixodes
spp. The anal
groove curves around the posterior part of the anus (Fig. 6) or is
absent. Eyes may be present or absent
_ _ _ _ _ 2 2. Eyes are absent _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ 3 Eyes are
present_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4 3. Festoons are not
ornate. Palpi are short, conical when
closed and segment #2 projects laterally most of the time beyond the basis
capituli (Fig. 2). Coxa #1 is never bifid (Cosmopolitan) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Haemaphysalis spp. Festoons
are ornate. Palpi are long and
segment #2 is very long (occur on reptiles in the tropics)_ _ _ _ _ _ _ _ _ Aponomma spp. 4. Anal groove is absent or
inconspicuous. Species not
ornate. Eyes are present and
marginal. Festoons are absent. Palpi are very
short. The 2nd and 3rd
segments are compressed and ridged dorsally and laterally. Males have adanal and accessory shields
(tropical and subtropical species)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ Boophilus spp. Anal
groove is conspicuous. Ornate or
inornate species but without all of the previous characteristics _ _ _ _
_ _ _ _ _ _ _ _ _ 5 5. The body is ornate. The eyes are marginal and festoons are
present. The abdomen does not have a
pair of terminal extensions tha t are
capped by sclerotized points _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ 6 Body is
usually not ornate, but if it is (e.g. in Hyalomma & Rhipicephalus)
then there are a pair of abdominal extension capped
by sclerotized points _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ 7 6. Palps are short with
their 2nd segment not two-times as long as wide. The hypostome has denticles lying in 6 rows, one each side
(e.g., 3/3) and taking up most of its length (Cosmopolitan species) _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Dermacentor
spp. Palps are
long with the 2nd segment two-times as long as wide. The hypostome has denticles that are
confined to the apical 1/2 and usually
arranged 3/4 or 4/4 (Tropical & subtropical species) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ Amblyomma spp. 7. The eyes are not on the
scutum margin but more inward. If
ornate then with a pair of abdominal extension capped by sclerotized points
(Eastern Hemisphere tropical & subtropical species) _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Hyalomma spp. Eyes are
located on the scutum margin. There
are no abdominal extensions _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ 8 8. Ventral shields or
plates are absent in both sexes _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
9 Ventral
shields are present in males but absent in females. The basis capituli are usually hexagonal when viewed from the
top.
(Cosmopolitan) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Rhipicephalus spp. 9. The basis capituli are
rectangular viewed from above. The
coxae from #1 through #4 are all about equal in size, but coxa #4 does not
have spines. The spiracles are not
complete circular (American tropics species)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Otocentor spp. The basis
capituli are hexagonal viewed from above.
Coxae increase a lot in size from #1 through #4. Coxa #4 bears very long
spines. Spiracles are shaped
like a comma (African species) _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Rhipicentor
spp. Genus: DERMACENTOR There have been more than
320 species of Ixodidae described with members that are of medical
importance. The genus Dermacentor is of especial importance because
there are species that are serious vectors of human disease. The following key is restricted to species
from North America, and a contemporary literature search is advised to find
serious vectors from geographical areas. 1. Spurs present on coxa
#1, diverging outwards from their base (Western North America) _ Dermacentor parumapertus Neum. The spurs
on coxa #1 have their proximal edges almost parallel or slightly diverging
near the apices _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 2. The spiracular plate is
oval and without a dorsal extension but with a few large goblets (North
America) _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ Dermacentor albipictus
Pack.
Spiracular plate is oval and with a dorsal extension. The goblets numbers are abundant or
moderate. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 3. The coruna is long and
particularly in males (Central Pacific coast of North America) _ _ _ _ Dermacentor occidentalis Marx The
coruna is short or only of moderate length _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4 4. The spiracular plate
goblets are very abundant but small (Eastern North America) _ _ _ _ _ _ _ _ _
Dermacentor variabilis
Say The
goblets large and not as numerous or dense (Western North Amer.) (Fig. 6, Fig. 7)_ _ _ _ Dermacentor
andersoni Stiles Superfamily: PARASITOIDEA Within
the Parasitoidea the three families have structures that resemble those found
in the ticks. Tracheae are present,
which open through spiracles located on plates located usually above and
between coxa #3 and #4. Mouthparts
are well developed and have piercing chelicerae, an unarmed hypostome and a
pair of small palps. Ventral surfaces
have no furrows but rather sclerotized plates. Only the Dermanyssidae are of medical concern as the species
are true parasites of reptiles, birds and mammals. Chelicerae are like needles and mostly without teeth. Anal and ventral plates are usually
present and separate. The dorsal
plate covers only part of the body.
Two genera (Liponyssus
and Dermanyssus) attack humans and can transmit disease. Family: DERMANYSSIDAE 1. Chelicerae are shears and both arms are
present (Fig.
8-A) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ Liponyssus
spp. 2. Chelicerae are long needles (8-B) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Dermanyssus spp. Superfamily: SARCOPTOIDEA The mites of this group
do not possess trachea. All species
are parasitic attacking birds, mammals and insects. Most of the external structures associated with mites are much
reduced or absent. The mouthparts are
modified and reduced (Fig. 9). The segmentation of palps is not prominent as in ticks, and
they are frequently fused with the mouthparts. Chelicerae are reduced to sclerotized blades and a hpostome is
absent. The body integument is marked
with parallel folds. Tiny setae,
spines and cones occur on the dorsum.
The legs are short and often adapted for clasping. Legs often terminate in a stalked sucker
or long hair, and the two anterior leg pairs are widely separated from the
two posterior ones. These mites live on their
hosts for their entire life. They
infest skin, tissues, hairs or feathers.
Sexual dimorphism is often present, and the males have special
structures for clasping. Families may
be separated in the following key, which includes those not attacking humans: Key to Families of Sarcoptoidea 1. Mites equipped with
special structures that are adapted for clinging to hairs. These may be either modified chelicerae or
legs. Species
are parasitic on mammals and are of minimal importance for humans _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Listrophoridae No
clinging structures are present _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 2. Species infest the feathers
of birds primarily and are often heavily sclerotized _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ Analgesidae Species
do not inhabit the feathers of birds.
They have soft-bodies _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ 3 3. Species parasitize only
insects _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ Canestriniidae Species
parasitize the tissues of vertebrates _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4 4. The vulva is
longitudinal. Species parasitize the
skin and tissues of birds _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Cytoleichidae Vulva is
transverse and species parasitize the skin of mammals and birds _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Sarcoptidae Family: SARCOPTIDAE The Sarcoptidae produce
skin diseases of humans and animals that are called scabies, acariasis,
etc. All species infest the skin and
live mainly underneath scabby incrustations that are caused by their feeding
activity. Some species, e.g. Sarcoptes spp,
burrow to form tunnels below the skin surface. There are many genera in the family, but those of primary
medical importance are considered presently. 1. The tarsal suckers bear
segmented pedicels. Males have anal
suckers (Fig.
10) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Psoroptes
spp. Sucker
pedicels are not segmented or may be absent entirely (Fig. 11)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 2. Females lack tarsal
suckers on all legs. The anal opening
is terminal. Species parasitize
birds_ _ _ _ _ _ _ Cnemidocoptes spp. Females
possess tarsal suckers on some legs _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 3. Tarsal suckers on all
legs of males and on the 1st, 2nd & 4th legs of females. Species infest cattle and horses _ _ Chorioptes spp. Tarsal
suckers are not arranged as previous.
Suckers occur on the 1st, 2nd & 4th leg pairs of males and on the
1st & 2nd pairs of
females (Fig. 11) _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ 4 4. The anal opening is on
the dorsum. The dorsal surface of the
body only has short, sharp setae _ _
_ _ _ _ _ _ _ _ Notoedres
spp. Anal
opening is terminal or partly ventral.
The body's dorsum has pointed scales and stout spines (Fig. 11) Superfamily: TROMBIDOIDEA This is a large group of
mites that feed on plant juices or they are predaceous. Some species are parasitic while others are
free-living in the nymphal and adult stages and parasitic in the larval
stage. They possess trachea and the
spiracles are situated on or near the bases of the chelicerae. Mouthparts may be either prominent and
raptorial or modified for piercing and sucking. The final segment of the palpus is modified as a thumblike
structure that can appose a clawlike extension of the penultimate
segment. They are never heavily
sclerotized and chitinous plates are usually absent. There about 6 families,
but only one, the Trombidiidae is of medical importance as it has species
that may be parasitic on humans and animals in the larval stage. Other families have parasitic habits but
are of minor importance. Two
subfamilies, Trombidiinae and Trombiculinae, may actually be distinct
families according to some specialists. Family: TROMBIDIIDAE Examples: (Eutrombicula alfreddugesii,
Eutrombicula batatas,
Trombicula autumnalis & Trombicula akamushi) 1. The abdomen of adults and nymphs is much
constricted in front of the middle portion.
The eyes, if present, are never stalked.
Eggs are laid singly. Larvae are parasitic on vertebrates _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Trombiculinae, 2nd View 2. The abdomen of adults
and nymphs is not constricted. The
eyes are usually present and often stalked.
Eggs are laid in clusters. Larvae
are parasitic on invertebrates _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Trombidiinae Key References: <medvet.ref.htm> <Hexapoda> Banks, N. A. 1915. The Acarina or mites. U.S. Dept. Agr. Rept. 108. Bishopp, F. C. 1935. Ticks and the role they play in the
transmission of diseases. Rept.
Smithsonian Inst. for 1933: pp
389-406. Bishopp, F. C. & H. L. Trembley.
1945. Distribution of certain
North American ticks. J.
Parasitology:: 31-1-54. Bishopp, F. C. & H. P. Wood.
1913. The biology of some
North American ticks of the genus Dermacentor. Parasitology 6:
153-87. Cooley, R. A. 1942. Determination of Ornithodoros species: Symposium on relapsing fevers in the
Americas. Amer. Assoc. Adv. Sci. Pub 18:
77-84. Ewing, H. E.
1926. Key to the known adult
trombiculas (adults of chiggers) of the New World with descriptions of two
new species (Acarina, Trombidoidea) Ent.News 37: 111-13. Ewing, H. E. 1944.
The trombiculid mites (chigger mites) and their relation to
disease. J. Parasitology 30: 339-65. Service, M. 2008. Medical Entomology For Students. Cambridge Univ. Press. 289 p Legner, E. F. 1995. Biological control of Diptera of medical and veterinary
importance. J. Vector Ecology 20(1):
59-120. Legner,
E. F. 2000. Biological control of aquatic
Diptera. p. 847-70. Contributions to a Manual of Palaearctic
Diptera, Vol. 1, Science
Herald, Budapest. 978 p. Matheson, R. 1950. Medical Entomology. Comstock Publ. Co, Inc. 610 p. Vitzhum, H. G.
1942. Acarina. In: Bronns, Klassen & Ordnungen des
Tierreichs. Funfter Band, IV
Abteilung 5 Buch 1-3 Lieferung 1-1011.
Leipzig |
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