The spiders and mites

ARACHNIDA

Araneae (spiders)

The spiders are all small black or dark brown animals with a maximum body length of 3mm (pictures).  They are extremely common and can be seen under stones and logs, often remaining stationary for 4 or 5 seconds after the stone has been overturned before suddenly spring into life and escaping.  It is also common to find the remains of

 

egg cocoons or sometimes cocoons with unhatched eggs and the parent still guarding. There are only a few records of spiders in houses.  The species from Svalbard are adapted to the Svalbard environment and rarely enter houses.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Acari (mites)

Some 140 species of mite are known from Svalbard.  The majority are small innocuous animals living in the soil, however, some can be often seen running about over rocks on warm days.   The mites can be divided into three groups, the hard bodied (oribatids) and the soft bodied (mesostigmatids and prostigmatids) mites.  The hard-bodied mites have the greatest diversity on Svalbard with over 80 species recorded.  These animals live in the soil and feed mostly on dead plant material or fungae.  Although they are very small, less than one millimetre long, they often live many years.  One species had its life cycle described recently and was found to take five years to become adult. 

Less is known about the soft bodied mites.  They are often predatory feeding on other mites as well as other invertebrates.  They also have a shorter life cycle although the life cycle on Svalbard is unknown.