Identification / General characteristics of tick genera (hard and soft ticks)
Although most people consider ticks to be either small and red or large and blue, on closer inspection many species are extremely colourful when examined under a stereoscopic microscope. The range of colours or ornamentation on the scutum, particularly of the males of certain species, is spectacular, from metallic mauve, shiny dark orange, bright yellow to iridescent green. The legs of certain species may also differ in colour from that of the scutum and the posterior edge of each segment of the legs may be encircled by an ivory-coloured band. Some of these features can readily be seen with the naked eye and the ticks have been given common names by farmers and researchers. Thus we have bont (brightly coloured) ticks, bont-legged ticks with ivory-coloured bands around their legs, red-legged ticks whose legs vary from light to dark orange, yellow dog ticks, and blue ticks, the last mentioned ticks acquiring their common name from the slaty blue colour of their engorged females.
The various genera of hard ticks can easily be differentiated by a set of features unique to each genus: mouthparts, basis capituli, scutum, eyes, festoons, adanal, subanal and accessory anal plates, coxae, anal groove.
The differentiating features of adult ticks of the different genera are listed below. If you master these you are nearly halfway to identify the tick to species level. An identification key to the families and genera can be downloaded here.
Characteristics of the different genera of hard ticks
Amblyomma
- Mouthparts very long, elongate second segment of palps
- Conscutum and scutum ornate
- Eyes present
- Festoons present
- Adanal plates on males absent, or when present very small
- Banded legs
- Three-host ticks
Amblyomma (previously Aponomma)
- Mouthparts long
- Conscutum and scutum ornate or inornate. Conscutum circular to laterally oval
- Eyes absent
- Festoons present, but inconspicuous in some species
- No adanal plates on males
- Three-host ticks
Rhipicephalus(previously Boophilus)
- Mouthparts very short, proximal margins of palpal segments II and III sclerotized and have the appearance of two protruding rings
- Conscutum often so poorly sclerotized that the dark pattern of the caeca can be seen from above
- Eyes present but not conspicuous
- No festoons
- Adanal plates and accessory adanal plates of males well developed
- Caudal process may be present in males
- One-host ticks
Dermacentor
- Mouthparts medium-length and broad
- Basis capituli rectangular
- Scutum ornate
- Eyes present
- Festoons present
- No adanal plates on males
- Males have large coxae, particularly the fourth pair. First pair with prominent posteriorly directed spurs
- Most species three-host, but some are one-host ticks
Haemaphysalis
- Mouthparts short and broad
- Basis capituli rectangular
- Scutum inornate
- Eyes absent
- Festoons present
- No adanal plates on males
- Three-host ticks
Hyalomma
- Mouthparts long, second segment of palps elongate
- Scutum pale to dark brown
- Eyes present and convex
- Festoons present
- Adanal, sub-anal, and accessory anal plates present on males
- Coxae of first pair of legs with long, prominent posteriorly directed spurs
- Banded legs
- Two or three-host ticks
Ixodes
- Mouthparts long.
- Auriculae latero-ventrally on basis capituli
- No eyes
- No festoons
- No adanal plates on males
- Anal groove conspicuous and anterior to the anus
- Legs appear to be grouped anteriorly
- Three-host ticks
Margaropus
- Mouthparts very short
- Conscutum thin and transparent and the dark pattern of the caeca can be seen from above
- Eyes present but not conspicuous
- No festoons
- Adanal plates on males well developed
- Caudal process and tufts of hairs present on posterior margin of males
- Banded legs
- The segments of the fourth pair of legs in males are markedly enlarged
- One-host ticks
Rhipicentor
- Mouthparts of medium length
- Eyes present
- Festoons present
- Adanal plates absent
- Coxae of first pair of legs with very prominent, long posteriorly directed spurs
- Coxae of fourth pair of legs in males very large, each with two long, narrow, pointed posteriorly directed spurs
- Three-host ticks
Rhipicephalus
- Mouthparts short to medium length.
- Basis capituli generally hexagonal in shape.
- Scutum usually uniformly brown, but four species have ivory-coloured ornamentation.
- Eyes present.
- Festoons present.
- Adanal plates, and usually also accessory adanal plates, present on males.
- Coxae of first pair of legs with long, prominent posteriorly directed spurs .
- Majority are three-host ticks, but a few species require only two hosts.
In summary the most prominent features that you must focus on when deciding to which genus a particular specimen of a tick belongs to are:
- Length of mouthparts
- Eyes or eyeless
- Conscutum ornate or inornate
- Colour of legs
- Festoons or no festoons
- Anal plates or no anal plates.
Characteristics of the different genera of soft ticks
Argas
- Integument leathery
- Mouthparts recessed ventrally and not visible from above (except in larvae)
- Eyes absent
- Spiracular plate postero-laterally between 3rd and 4th pair of legs
- Numerous symmetrically arranged discs on dorsal side of body
- Lateral margin sharp with row of quadrangular cells on both the dorsal and ventral surfaces
- Sexual dimorphism limited mainly to the genital aperture
- Several nymphal stages
Otobius
- Dark, violin-shaped adults
- Mouthparts recessed ventrally and not visible from above (except in larvae)
- No lateral suture line on adults
- Nymphs diamond-shaped becoming violin-shaped with numerous spines on the body
- Larvae pear-shaped with clearly visibly anteriorly projecting mouthparts
Ornithodoros
- Leathery-mammillated integument
- Mouthparts recessed ventrally and not visible from above (except in larvae)
- Body margin rounded
- Supra-coxal fold
- Eyes absent or two pairs in the supra-coxal fold.
