Category Archives: Arachnids

Fishing spiders (Dolomedes spp.)

fishing spider (Dolomedes sp.)
Photo by Alissa H.

Dolomedes is a large species of nursery web spiders known as fishing spiders, raft spiders, dock spiders or wharf spiders. There are more than 100 currently recognized species worldwide, 8 species in North America north of Mexico. Four species have been recorded in Minnesota.

Fishing spiders have a worldwide distribution, occurring on every continent except Antarctica. They are usually found near permanent bodies of water, or on floating vegetation in a body of water. Some are found in grassy meadows. One, dark fishing spider, wanders well away from water. One, white-banded fishing spider, lives in trees. The remainder are semiaquatic, spending part of their time in or on water.

Some fishing spiders sit quietly at the edge of a lake or pond or on floating vegetation. They rest their front three pairs of legs on the water surface to detect ripples or vibrations of prey. Others stalk prey on land. They eat mostly aquatic insects but also small fish. None hunt from webs, but all make nursery webs for their young.

All fishing spiders are covered with water repelling (hydrophobic) hairs. They are able to run across the surface of the water and even to “climb” under the surface to subdue prey. When they submerge, air is trapped on the underside of their abdomen, and they are able to breath underwater.

http://www.minnesotaseasons.com/Arachnids/fishing_spiders_Dolomedes.html

Common house spider (Parasteatoda tepidariorum)

common house spider (Parasteatoda tepidariorum)
Photo by Alfredo Colon

Common house spider (Parasteatoda tepidariorum) is the most common house spider in the eastern United States. It has a cosmopolitan distribution, occurring on every continent except Antarctica. In the United States it is common east of the Great Plains and west of the Rocky Mountains, uncommon between.

Common house spider is found in and around human dwellings, sheds, barns, and privies, in stables, under highway bridges, and in culverts. It appears year-round when indoors, but it cannot survive northern winters outdoors. Its web is often built in upper angles of rooms and in corners of window frames and doorways. It hunts at night, hanging upside-down in the middle of the web. During the day it retreats into a corner or a crack.

Common house spider is a medium-sized colorful comb-footed spider. The front part of the body is short, flat, highest in the middle, and yellowish-brown. The back part of the body is gray with white and dark markings. There is a dark horizontal line just before the highest point, white chevrons before the line, a white spot just behind the highest point, and dark chevrons behind the spot. On lighter individuals the markings are indistinct. On the male the abdomen is more slender. The legs are yellow with dark bands on the female, orangish on the male.

http://www.minnesotaseasons.com/Arachnids/common_house_spider.html

Orchard orbweaver (Leucauge venusta)

Orchard orbweaver

Orchard orbweaver (Leucauge venusta) is a sedentary, small, brilliantly colored, long-jawed orb weaver. It is one of the most common spiders in the eastern United States, but is less common in Minnesota, where it reaches the western extent of its range. It is found in forests, dense woodlands, woodland edges, shrubby meadows, gardens, and orchards.

The species name venusta is Latin for “beautiful” and it is easy to see why it was given to this spider. The abdomen is silvery-white with four pairs of dark stripes, a yellow stripe on each side, and often a pair of bright coppery-red spots toward the rear.

Charles Darwin collected this species in 1832 on his voyage of the Beagle. He named it Leucauge argyrobapta. Both names are from the Greek, Leucauge meaning “with a bright gleam,” and argyrobapta meaning “dipped in silver.” The specimen was lost after Darwin’s voyage back to London.

In 1973, as party of an experiment to study web building in zero gravity, two orchard weaver spiders were brought to the U.S. space station Skylab 3. After some time to adjust to weightlessness, the spiders constructed complete webs that were not much different than those constructed on earth.

Photo by Alfredo Colon

http://www.minnesotaseasons.com/Arachnids/orchard_orbweaver.html

Eastern harvestman (Leiobunum vittatum)

Eastern harvestman
Photo by Alfredo Colon

Eastern harvestman (Leiobunum vittatum) is a common, large, easily recognized harvestman. It occurs in the United States and southern Canada from the east coast to the Great Plains. In Minnesota it is common in the wooded eastern region, uncommon in the western prairie region.

The body is golden yellow to dark reddish-brown with a large, distinct, dark figure on the upper side. In summer the figure contrasts sharply with the lighter background. As the season progresses both sexes become progressively darker. By mid-fall they can be almost black.

The legs are extremely long and slender. The patella is short and dark. There is also a dark band at the outer end of the tibia. On the female the legs are light brown with contrasting dark rings. On the male the legs are dark brown and less contrasting.

http://www.minnesotaseasons.com/Arachnids/eastern_harvestman.html

Brilliant jumping spider (Phidippus clarus)

brilliant jumping spider

Photo by Alfredo Colon

Brilliant jumping spider (Phidippus clarus) occurs across North America from coast to coast. It is very common in Minnesota. A study in 1997 surveyed jumping spiders in 30 locations around Minnesota. The author collected 572 jumping spiders representing 15 species. Brilliant jumping spider was by far the most common, with 299 specimens (52%) collected.

Brilliant jumping spider is found from July to September in moderately moist fields on grasses and perennial plants. It is a small to medium-sized spider (order Araneae) but a relatively large jumping spider (family Salticidae). Adults are mostly black with four pairs of white spots and two red stripes on the abdomen.

The female is a paragon of parental perseverance. In the fall she creates a large white egg sac at the top of a tall grass or herbaceous plant and drops eggs into the sac. She prevents the eggs from drying out by repeatedly adding silk to cover the egg mass. She stays with the egg sac until the young disperse in about a month. During this time she does not feed and usually dies from starvation a few days later.

http://www.minnesotaseasons.com/Arachnids/brilliant_jumping_spider.html

Crimson erineum mite (Aceria elongatus)

crimson erineum mite

At only one tenth the width of a human hair in length, a crimson erineum mite (Aceria elongatus) is barely visible to the human eye unaided by magnification. Its claws, dorsal shield markings, and other identifying body features are not. Identification in the field is possible only by noting the properties of the abnormal growths (galls) it produces on its host.

Crimson erineum mite is a plant parasite infecting only sugar maple and possibly black maple. It is common in eastern United States and Canada. When injured by a mite, a leaf cell produces a small projection filled with colored fluid on the upper surface. Small patches of these are usually scattered over the leaf surface. They are greenish-white at first, soon becoming crimson or purplish. They reach their maximum extent, and are most noticeable, in summer. The infestation is sometimes abundant and can cause leaf distortion and premature leaf drop.

http://www.minnesotaseasons.com/Arachnids/crimson_erineum_mite.html

Marbled orbweaver (Araneus marmoreus)

marbled orbweaver

Photo by Christa Rittberg

Orb weaver spiders (Aranidae) is the third largest family of spiders. There are about 3,100 species in 169 genera worldwide. They spin a large circular web that hangs vertically. This web is called an “orb”, which gives this family its common name.

Marbled orbweaver (Araneus marmoreus) is a medium-sized orb weaver spider. Females are about twice the size of males. They are highly variable in appearance, but all have a light colored abdomen with black, gray, and white markings, at least at the front edge, that give them a marbled appearance.

The marbled orbweaver orb is a closed hub, 20″ to 30″ in diameter, with 15 to 35 spokes (radii) that are not sticky. The radii extend to the center of the hub and are connected to each other by sticky threads that spiral outward from the center. The spider also makes a retreat out of silk near one edge of the orb. The retreat is connected by a signal thread to the center of the web, allowing the spider to feel vibrations of prey. The web is usually consumed and a new web constructed each evening.

http://www.minnesotaseasons.com/Arachnids/marbled_orbweaver.html

Bold jumper (Phidippus audax)

bold jumper

Photo by Terry Hayes

Bold jumper (Phidippus audax) is an extremely common jumping spider in eastern United States. It is a medium-sized spider but a very large jumping spider. It can be found from spring to fall in old fields, prairies, open woodlands, backyards, gardens, and human houses.

The most distinctive feature of this spider is the iridescent green or blue mouthparts. Both sexes share this feature, but when courting, the male will wave its forelegs and sense organs (palps), showing off his colorful parts.

Bold jumpers hunt during the day, not at night. They sneak up on their prey and pounce, releasing silk while jumping as a drag line to prevent falling. They will bite if molested but are usually too quick and wary to be caught. They can jump 10 to 50 times their body length.

There are about 5,000 species of jumping spiders. Bold jumper is distinguished by its large size; conspicuous, iridescent green or blue mouthparts; massive, high, front body segment with rounded sides; four pairs of matte black spots on the abdomen; the arrangement of usually four pairs of white spots on the abdomen; and its occurrence in the northern United States.

http://minnesotaseasons.com/Arachnids/bold_jumper.html

Ant-mimicking jumping spider (Synemosyna formica)

ant-mimicking jumping spider

Photo by Terry Hayes

Ant-mimicking jumping spider (Synemosyna formica) is often overlooked and mistaken for an ant. It is found in bushes and tall grass from Vermont to Georgia west to Minnesota and Texas.

Most jumping spiders have furry round bodies. Ant-mimicking jumping spider is a Batesian mimic, evolved to imitate the appearance of ants which are avoided by ants, mantises, and larger jumping spiders. The ant-like modifications include a constricted abdomen and front legs that are curved, mimicking ant antennae.

There are more than 300 species of spiders that are ant mimics. Ant-mimicking jumping spider is distinguished by a sharp downward slope between the head portion and the thorax portion of the cephalothorax; narrow, parallel-sided rear portion of the cephalothorax; white or pale marks at the abdominal constriction; and in the palpal bulbs of the male the embolus is fixed to the tegulum.

http://minnesotaseasons.com/Arachnids/ant-mimicking_jumping_spider.html

Dark fishing spider (Dolomedes tenebrosus)

dark fishing spider

Photo by Brian Johnson

Dark fishing spider (Dolomedes tenebrosus) is a large, robust, nursery web spider (family Pisauridae). The common name is misleading, as this spider is most often found in deciduous forests, often far from water.

This is the largest fishing spider (genus Dolomedes). The adult female body can be up to 1″ long with a legspan of over 3″. The male is about half that size and one-fourteenth the weight. The body is light brown with dark markings and the legs have alternating light and dark bands.

The male never survives the mating process. This is not because it is killed by the female, as with black widow spiders. The male has evolved to die spontaneously after mating, providing the female with a meal to nourish her eggs.

Fishing spiders are similar to, and often mistaken for, wolf spiders. They are distinguished by the arrangement of their eyes and the mode of perching. Dark fishing spider is similar in appearance to striped fishing spider (Dolomedes scriptus) but is larger and has less white marking on the abdomen.

http://minnesotaseasons.com/Arachnids/dark_fishing_spider.html