Feeding

 

 

Ticks ‘quest’ for a host at the tip of grass blades etc where they:

  • wave their front legs in the direction of an approaching animal and if it brushes by and is suitable, the ticks climb aboard
  • host stimuli are detected by setae in Haller’s organ and on the tip of the front legs and palps - different setae are sensitive to, for example, vibrations, carbon dioxide, temperature and humidity

 

Ticks dehydrate if they fail to find a host. To avoid this, they periodically move back down to the humid vegetation layer to absorb water. Then they ascend to try again.

 

Before a tick feeds, it pierces the skin using the serrated digits of the chelicerae. The toothed hypostome is worked into the wound by rocking motions and it acts as an anchor. Salivary glands secrete a cement round the feeding tube formed by the hypostome and chelicerae. This also fixes the tick to its host.

 

Wound formation damages adjacent tissue and blood capillaries, while salivary secretions are thought to cause haemorrhaging. A blood pool forms as a result. Blood is sucked up the feeding tube in approximately 30 second bursts. After a rest, more salivary secretions are injected into the host’s tissues.

 

Once fully fed (engorged), ticks detach by retracting the chelicerae and loosening the hypostome from the cement by muscular movements of the mouthparts.

 

Larvae feed for 2--6 days, nymphs for 3--8 days, and females for 6—12 days.

 

Females expand enormously during feeding. They increase in length from about 3mm (unfed) to 11mm (engorged). They also change colour from deep yellow to blue-grey.

 

Males feed only briefly, if at all, and there is little size increase. Their length ranges from about 2.2 to 2.8mm.