Life cycle

High season for castor bean tick in June

Fig. 66. Ticks are active in the months with temperatures above 7 0 C during daytime.

When the blood-filled female tick has let herself fall, she can lay eggs a few days later. About 2,000 eggs are laid. A reasonable number considering the poor chance of finding hosts. From the eggs, tiny, six-legged larvae hatch, and they are very hungry. They sit on blades of grass or the like. Here, they can sit for days, waiting for an animal (or human) to pass by. If this happens, they quickly climb onto the host.

They crawl around on the host until they have found a suitable thin-skinned place to bite. 5-6 days later, they are full and let themselves fall to the ground. Here they hide, digest and molt. The next stage, the nymphal stage, has eight legs and is so big that you can clearly see that it is a tick. It finds a host, sucks blood and hides in vegetation. The last stage is adult males and females. They mate, suck blood and the female lays eggs. They overwinter under moss and other undergrowth. The life cycle takes up to 1/2 years. Sucking ticks are almost exclusively found during spring and autumn.

The castor bean tick

Castor bean tick attacks with its front pair of legs

Fig. 65. The castor bean tick – ready to climb onto a host with the front pair of legs. (Gjelstrup)

The castor bean tick

The castor bean tick

The castor bean tick, Ixodes ricinus, is just one of about thirty kinds of ticks that are found in Denmark. However, it is almost exclusively this species of ticks that is found on humans. An adult male tick is approx. 2 mm long. The female is twice as long. Ticks engorge when they suck blood. The abdomen’s reddish-brown, leathery skin can expand quite a lot.

A blood filled female castor bean tick can be almost 1.5 cm long and looks like a pea, ranging in color from a grayish yellow to blue-gray. In some places in Denmark, the castor bean ticks are very common. In other parts, they are hardly seen. The reason is that they have rather strict requirements to the environment. They do not tolerate dehydration and are therefore mostly found in underwoods and other densely-vegetation locations. The castor bean tick can be seen on reptiles, but it is much more frequently found on mammals and birds. In Denmark, roe deer serve as the primary hosts. In areas with cattle or sheep, these often serve as hosts.