The spiders and mites

ARACHNIDA

The terrestrial Arachnida in Svalbard are comprised of the spiders and the mites. The majority of the spider species (and individuals) belong to the family Linyphiidae (money spiders), are small and black. The mites can be largely divided into the hard-bodied Oribatidae and the soft-bodied Mesostogmata and Prostigmata. To the mites also belong the seabird tick that has been becoming more common in Svalbard during recent years.

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. Spiders under a stone.

<i>Hilaria glacialis</I> — Adult spider, *Hilaria glacialis*

<i>C. spetsbergensis</I> — *C. spetsbergensis*

<i>Erigone psychrophila</I> — *Erigone psychrophila*

<i>Erigone arctica paleoarctica</I> — *Erigone arctica paleoarctica*

<i>Mughiphantes sobrius</i>, with characteristic colouration. — *Mughiphantes sobrius* displaying characteristic colouration.

Acari (mites)

<i>Ameronothrus lineatus</I> mites gathered together under a stone, Blomstrandhaløya, June 2008. — *Ameronothrus lineatus* mites gathered together under a stone, Blomstrandhaløya, June 2008.

Two oribatid mite species. On the left <i>Diapterobates notatus</i> (adult and juvenile) and on the right <i>Oribatula tibialis</i>. Both are around 1mm in length and live in the soil surface. — Two oribatid mite species. On the left *Diapterobates notatus* (adult and juvenile) and on the right *Oribatula tibialis*. Both are around 1mm in length and live in the soil surface.

Left <i>Mycobates sarakensis</i>, right <i>Tectocephus velatus</i> — Left: *Mycobates sarakensis*. Right: *Tectocephus velatus*.

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.

Oribatid mite <i>Ameronothrus lineatus</i>. Collected Blomstrandhalvøya. Species common under rocks close to the coastline. Approximately one mm in length. — Oribatid mite *Ameronothrus lineatus*. Collected Blomstrandhalvøya. Species common under rocks close to the coastline. Approximately one mm in length.

Left <i>Camisia anomia</i>, right <i>Camisia foveolata</i> — Left: *Camisia anomia.* Rght: *Camisia foveolata.*

Left <i>Hermannia reticulata</i> juveniles, right <i>H. reticulata</i> adult — Left: *Hermannia reticulata* (juveniles). Right: *H. reticulata* (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.

Predation in action. Prostigmatid (soft bodied) mite devouring a colleague.

<i>Thinoseius spinosus</i> deutonymph — A soft-bodied mite (Mesostigmata) *Thinoseius spinosus* (juvenile, deutonymph).

<i>Arctoseius haarlovi</i> female — *Arctoseius haarlovi* (adult female).

Aphid (<i>Acyrthosiphon svalbardicum<I>) being attacked by predatory mite larva. — Aphid (*Acyrthosiphon svalbardicum*) being attacked by predatory mite larva.

<i>Zercon</I> sp. mite. — *Zercon* sp. mite.

Predatory mites on beach, *Neomolgus litteralis*

Juvenile mite, left <i>Thinoseius spinosus</I> (deutonymph) found attached to adult fly, right <i>Protophormia terraenovae</I>. The young of this species of mite attach themselves to a fly host so as to be travel to new areas. — Juvenile gamasid mite, left *Thinoseius spinosus* (deutonymph) found attached to adult fly and on right *Protophormia terraenovae*. The young of this species of mite attach themselves to a fly host so as to be travel to new areas.

Gamasid mite <i>Arctoseuis</i> species. — Gamasid mite, *Arctoseuis* species.

Gamasid mite <i>Zercon </i> species. — Gamasid mite, *Zercon* species.

Soft bodied predatory mites. Both around than 2mm in length.

Prostigmatid mite — Soft-bodied prostigmatid mite

Prostigmatid mite and thumb - small animals!

Ticks

Recently the parastitic bird tick has been reported from Spitsbergen. The tick appears to be widespread in Bjørnøya (Bear Island) but has been rarely seen, until recently, on Spitsbergen. Here, the majority of seabirds have few, if any ticks. Nonetheless, some birds from a few colonies including Brunnichs guillimots and kittiwakes, appear to be infested. The reasons for these observations are unclear. However recent work in Svalbard has revealed a possible link between warmer winter conditions and increased prevalence on the seabirds (see paper Descamp 2013 click here). Hence, the warmer winter conditions projected by climate change models may lead to an increase in rick occurence in the sea bird colonies in Svalbard.

Seabird tick <i>Ixodes uriae</i> — Seabird tick, *Ixodes uriae*.