Biology

Itch mite passage with female itch mite

Fig. 73. Itch mite burrow. The female mite, and behind her excrement and eggs. (Railliet)

The itch mite eats the stratum corneum of the skin. A female itch mite lays 2-3 eggs a day. They are attached to the bottom of the burrow with a short stem. Newly laid eggs are 0.170 mm long and half as wide. The eggs hatch after 3-4 days and a small, six-legged larva crawls out. They find their way to the skin surface through a hole in the burrow roof and dig a short vertical burrow nearby for themselves. 3-4 days later, they molt, turning into the nymphs which have 8 legs.

After another period of 3-4 days they molt again and are either turned into males or the second nymph stage, which later turns into a female. As a result, the females are larger than males. The female and the male mate in folds of the skin. After mating, the males die and the females burrow into the skin – this takes about half an hour. Here she makes a tunnel which is parallel to the skin surface. Two days later, the first egg is laid. The rest of the female mites’ life is spent laying eggs. At the same time, the mite is digging its way through the skin, digging 0.5-5 mm each day, the burrows may be several centimeters long.

The female itch mite is not bound to her burrow. She can choose to move away and start a new burrow elsewhere on the skin. The development time from egg to egg is between two and three weeks. There is a high mortality rate; only 10% of the laid eggs become adult mites.