About ticks

Ticks are not insects, but acarines, their closest relatives are mites, spiders and scorpions. Whereas adult insects have six legs, adult acarines have eight.

Free-living ticks tend not to walk very far. They mostly climb onto vegetation and wait for the next suitable host to come along (Figure 1). All ticks feed on blood during some stage of their life. When a potential host comes near, the waiting ticks become active; they wave their front legs about in what is known as questing behaviour. This is probably triggered by the host animal’s exhaled air (dry ice, which releases CO2, can be used to attract free-living ticks to traps in the ground).

Whereas 1-host ticks are fairly host-specific (although cattle ticks can be found on goats, hairy sheep, horses, and other animals, they prefer cattle), 2- and 3-host ticks infest animals of a variety of species. The larvae and nymphs will take their blood meal on small ground-dwelling animals or birds. This means that they can be carried over long distances by these intermediate hosts in the absence of any livestock host animals. The bush tick (Haemaphysalis longicornis) and the paralysis tick (Ixodes holocyclus) are 3-host ticks.

Adult ticks’ bodies basically consist of an abdomen, from which protrude the four mouthparts (held closely together, until the tick attaches to take a blood meal), and the eight legs (Figure 2). There is no head and the commonly held belief that the head will break off and remain when the tick is pulled off the host is incorrect.

Figure 1. Larval cattle ticks on grass showing questing behaviour. Image credit Ralph Stutchbury
Figure 1. Larval cattle ticks on grass showing questing behaviour. Image credit Ralph Stutchbury
Figure 2. Adult female paralysis tick held in tweezers showing the abdomen, 8 legs and mouthparts. Image credit Ala Tabor
Figure 2. Adult female paralysis tick held in tweezers showing the abdomen, 8 legs and mouthparts. Image credit Ala Tabor