August 21, 2023

Castianeira

Castianeira is the only genus from the family Corinnidae that has been found in Minnesota. Many of these are mimics of hymenopterans (not just ants but also velvet ants). Their bodies are longer than wide, often with white or orange hairs. These hairs may be dense or diffuse on the carapace but often form distinct bands on the abdomen. Males possess a sclerite (think armored plate) that covers much of the dorsal surface of the abdomen; this feature is often indistinct. In females, it is much smaller in size and positioned toward the anterior. The legs are thin and often have white longitudinal stripes. These spiders are active hunters and move very quickly across the ground. They can sometimes be found under rocks, logs or other debris in appropriate habitats.

Members of this genus are often confused with spiders in the genus Sergiolus or Micaria in the family Gnaphosidae; these genera can also be brightly colored, boldly patterned and ant-like. Confusion can also occur within members of the same species of Castianeira. Individuals may vary in their base color as well as the banded pattern of hairs on the abdomen (though sometimes this is due to physical wear and not genetics). Variation within species is described more thoroughly below.

C. amoena goes by the common name of Orange Ant-Mimic Sac Spider on iNaturalist and is the most distinctive member of this genus in Minnesota. It is bright orange over much of its body with black bands on the abdomen. Its overall appearance is designed to look like a female velvet ant which is not an ant at all but rather a brightly colored ant-like wasp. The bright, contrasting pattern is designed to warn unsuspecting people that they pack quite a sting if you choose to pick one up. Looking like such an insect may provide some protection to the spider. This is a southern species that reaches the northern limit of its distribution in Minnesota. It is typically found in non-forested areas and prefers areas with rock outcroppings (Reiskind, 1969). This species is only known from Rock County in the southwestern corner of the state. Example of this species: https://bugguide.net/node/view/491173/bgimage ; https://bugguide.net/node/view/161378/bgimage.

C. cingulata or Two-banded Ant-Mimic Sac Spider has two distinct morphs (both found in Minnesota). As the common name indicates, all morphs have two pale bands on the anterior half of an abdomen that is sometimes larger toward the posterior. The femurs have dark stripes (sometimes bordered with white) on the dorsal surface as well as the femurs' sides. The "black morph" resembles a Black Carpenter Ant (Camponotus pennsylvanicus); the body is dark brown to black overall with diffuse white scales on the carapace. The carapace of the "bicolored morph" is brown toward the posterior but much darker (black) at the anterior; its abdomen is generally dark brown to black. I think this morph resembles the New York Carpenter Ant (C. novaeboracensis). This species is more common in forested ecosystems where it actively hunts for prey in the leaf litter (Reiskind, 1969). It is currently known from 17 Minnesota counties across the state. Black Morph male: https://bugguide.net/node/view/327240/bgimage Bicolored Morph female: https://bugguide.net/node/view/1371351/bgimage.

C. descripta on iNaturalist is assigned the common name of Red-spotted Ant-Mimic Sac Spider (with two other species). Perhaps a better name for it would be the Variable Red-spotted Ant-Mimic Sac Spider. Reiskind (1969) indicates that the size of the red spot on the dorsal surface of the abdomen typically gets larger as you move south and west across this species' range. The examples found by iNaturalist observers suggest that in Minnesota, males typically have a red spot that covers much of the abdomen but the size of the red spot is highly variable in females (and not related to geography). Females also show variable amounts of white hairs on their abdomen, sometimes none and other times forming transverse bands or an alternating black and white pattern. This species can be found in prairies as well as woodlands (Reiskind, 1969) which may well explain its broad distribution. It is currently known from 25 counties across the state. One other note: In Minnesota, a black spider with red on the abdomen is much more likely to be this species than a Black Widow, especially away from the southeastern Mississippi River bluff counties where widows can be rarely found.. Various forms of this species: https://www.inaturalist.org/observations/175434003 ; https://www.inaturalist.org/observations/168721899 ; https://www.inaturalist.org/observations/5211141 ; https://www.inaturalist.org/observations/130564264.

C. longipalpa or Long-palped Ant-Mimic Sac Spider. The carapace can be brown to black with diffuse to dense white hairs. The abdomen is typically darker brown to black with transverse bands of white hairs that may not reach the lateral edges and may be conjoined at the median. Their legs may have white rings and longitudinal stripes. This species can be found in prairies and well as woodlands and has the broadest distribution for any member of the genus in North America (Reiskind, 1969). In Minnesota it is known from nine counties but likely occurs statewide. Some examples of this species: https://www.inaturalist.org/observations/132485817 ; https://www.inaturalist.org/observations/131886556 ; https://www.inaturalist.org/observations/5211156.

C. trilineata has not been assigned a common name on iNaturalist and is hypothetical in its occurrence in Minnesota. It is known from Wisconsin (Reiskind, 1969). The carapace is orange-brown and shiny and the abdomen is red-brown with two bands of white hairs on the anterior half of the abdomen and a shorter band toward the posterior. Guarisco (2021) indicates that this species is similar to C. cingulata but it lacks the dark longitudinal stripes on the femurs and its legs get paler distally. A research grade example from iNaturalist: https://www.inaturalist.org/observations/144861451.

SOURCES
Guarisco, Hank. 2021. Castianeira of Kansas. Newsletter of the American Arachnological Society. Number 87.

Reiskind, Jonathan. 1969. The spider subfamily Castianeirinae of North and Central America (Araneae, Clubionidae). Bulletin of the Museum of Comparative Zoology, 138:286-325.

Posted on August 21, 2023 02:38 PM by cheins1 cheins1 | 5 comments | Leave a comment

July 22, 2023

Phrurotimpus

Spiders in the genus Phrurotimpus are currently found in the equally difficult-to-pronounce family of Phrurolithidae (they've also been assigned to Clubionidae, Liocranidae and Corinnidae in their taxonomic history). According tot the World Spider Catalog, there are 26 described species with 23 of them known from North America (the other 3 are known from China). It is possible that there are additional species waiting to be discovered or at least described. Dondale & Redner indicated they thought that the genus was in need of revision (1982) and Platnick's revision of the palustris species group is the only work that has been done since (2019).

On iNaturalist this genus of spiders goes by the common name of Antmimic Corinnine Spiders which keeps with the theme of making their name difficult to say. Dondale and Redner (1982) described them as "somewhat antlike" but I have never considered them as such and there are several more convincing ant mimics in Minnesota's spider fauna. I prefer the common name of Guardstone Spiders which is often applied to the family. That name is consistent with my experience that they are often under rocks on the ground (though not exclusively).

The overall impression of these spiders is a small, slender, fast moving ground spider (Dondale and Redner, 1982 indicates a maximum of 3.5mm). The first pair of legs is longer than the others and in males is often marked with dark patellas and tibiae bordered by a pale band on the lower tibia. Males can have a iridescent sheen to them; females (and sometimes males) have a pattern of chevrons on their abdomen.

These spiders are found in the leaf litter as well as under logs and stones in a variety of habitats. Due to their quick movement and small size, they are challenging to capture alive. They overwinter in their penultimate instar (one molt away from maturity) and mature in late spring or early summer; females attach their shiny, flat, red egg sacs to the underside of stones (Dondale & Redner, 1982). An example of their egg sac can be seen here: https://bugguide.net/node/view/309186/bgimage.

The genus Phrurotimpus in Minnesota is represented by four species.

P. alarius is only known from two counties in Minnesota: Nicollet and Mille Lacs. Kaston (1948) indicates this species has black/gray spots [bands] on legs III and IV. A female can be seen here: https://www.inaturalist.org/observations/5288693.

P. borealis is known from six counties across the state. It is known from Fillmore County in the southeast west to Blue Earth County and north to Lake of the Woods and St. Louis Counties. Female: https://www.inaturalist.org/observations/5288727 and male in alcohol: https://www.inaturalist.org/observations/82077141.

P. certus was first found in the state in 2022 and is only known from Pipestone County at this time. These individuals were very brightly colored and I knew it would be a new species of Phrurotimpus for the state when I first saw them. Female: https://www.inaturalist.org/observations/123708947 and male:https://www.inaturalist.org/observations/123262525.

P. palustris is known from three counties in the southeastern part of the state: Rice, Wabasha and Winona. There are no pictures of this species on either iNaturalist or BugGuide yet and Minnesota records were gleaned from Platnick, 2019. Platnick indicates that this species has dark bands on Legs III and IV and therefore is most likely to be confused with P. alarius.

Happy spidering!

Sources:
Dondale, C. D. & James H. Redner. 1982. The sac spider of Canada and Alaska (Araneae: Clubionidae & Anyphaenidae). Agriculture Canada, 1724:1-194.

Kaston, B. J. 1948. Spiders of Connecticut. Bulletin of the Connecticut State Geological and Natural History Survey 70: 1-874.

Platnick, Norman I. 2019. The Guardstone Spiders of the Phrurotimpus palustris Group (Araneae, Phrurolithidae). American Museum Novitates 3944:1-29.

World Spider Catalog-Phrurotimpus: https://wsc.nmbe.ch/genus/576

Posted on July 22, 2023 04:29 PM by cheins1 cheins1 | 0 comments | Leave a comment

June 27, 2023

Fishing Spiders

27 June 2023

Spiders in the family Pisauridae are commonly called the fishing spiders or nursery web spiders. Though their name suggests habitat selection near water, that is not always the case. I would classify them as large spiders (for Minneosta) and adult female Dolomedes can rival in size the Tigrosa wolf spiders mentioned in the previous post. In fact, due to their size and habits, they are often mistaken for wolf spiders. All of these species have a pretty widespread distribution in Minnesota and are commonly encountered.

Like wolf spiders, female fishing spiders can sometimes be found carrying a round egg sac with them as they traverse the landscape. Unlike the wolf spiders which attach that egg case to the spinnerets at the rear and always seem to be chased by a little round ball, the fishing spiders carry their egg sac using their chelicerae and therefore the egg sac is carried up front or under the body as they walk on their tiptoes (see https://bugguide.net/node/view/827127). Once the young have developed to a point that they are ready to leave the egg case, she finds a suitable location and creates a "nursery web". She often guards the nursery until the spiderlings have emerged and dispersed. An image of a Dolomedes striatus guarding her nest can be seen here: https://www.inaturalist.org/observations/53694419. An image of a D. tenebrosus can be seen here: https://www.inaturalist.org/observations/166245114.

In Minnesota we have 2 genera and 5 species.

The genus Dolomedes is represented by four species in Minnesota that I would divide into two different identification groups.

GROUP 1: brown-gray species
Dolomedes tenebrosus or Dark Fishing Spider is one of the most common species observers have found for the Spiders of Minnesota Project (>500 observations). This species is the most likely member of the genus to be found away from water where they often occur in wooded habitats. The W-pattern on its abdomen typically has white on the lateral portions of the W only. It also has a dark area below the eyes and a relatively unmarked carapace; the lateral edges can sometimes be white. A typical female: https://www.inaturalist.org/observations/166241082. The skinnier male: https://bugguide.net/node/view/2186027.

Dolomedes scriptus or Striped Fishing Spider is very similar in appearance to D. tenebrosus. It also has a W-pattern on the abdomen but the pattern is more bold and often has white along the entire edge of the W (not always). The carapace often has a pale midline and sometimes a lyre-like pattern as well. Some individuals may have white lateral edges to the carapace as well. In my experience, this species is more closely tied to water and I associate them with rocks and cliffs near water. A boldly marked individual: https://www.inaturalist.org/observations/124645587. A white-edged individual: https://www.inaturalist.org/observations/123923653.

GROUP 2: red-brown species
Dolomedes triton or Six-spotted Fishing Spider is commonly found near vegetated wetlands and sometimes can be found hunting for small fish and other aquatic prey on top of the water. The carapace has white sub-marginal stripes that flow into white longitudinal stripes on the abdomen. In the darker median area of the abdomen there are 6 pairs of distinct white spots (usually). A typical individual: https://www.inaturalist.org/observations/4068649.

Dolomedes striatus or Striped Fishing Spider (this is why we use those Latin names) is often found in wetlands, wet prairies and open bogs. This species is similar to D. triton. The white sub-marginal bands on the carapace are typically bolder and the red-brown median area of the carapace is darker adjacent to those white bands (unlike D. triton in which the median area is uniform in color). They also lack the distinct white spots on the abdomen. A typical female: https://www.inaturalist.org/observations/144795766. The very rare fulviatronotatus morph of this species has been found a couple of times in Minnesota and looks unlike any other member of this genus. See https://www.inaturalist.org/observations/184108563.

The last member of this family that is found in Minnesota is Pisaurina mira or American Nursery Web Spider. It is just as likely to be found in shrubs or the herb layer of a woodland as it is in a prairie and I find them often along woodland edges. This species is highly variable in its appearance and some of the drabbest individuals seem to lack any distinct markings at all. These can still be identified by this species' tendency to hold its two pairs of front legs forward and together (sometimes the rear pairs of legs are held together as well). An example of this posture can be seen here: https://www.inaturalist.org/observations/119772945

Examples of P. mira morphs:
"Red Morph": https://www.inaturalist.org/observations/54100189
"Stripe Morph": https://www.inaturalist.org/observations/91207051
"Drab Morph": https://www.inaturalist.org/observations/81516030

Happy spidering!

Posted on June 27, 2023 02:35 PM by cheins1 cheins1 | 2 comments | Leave a comment

May 27, 2023

Tigrosa

27 May 2023

Tigrosa means "fierce like a tiger"(Brady, 2012) and is an apt name for some of North America's largest wolf spiders. Though these are also some of the largest spiders in Minnesota, I rarely encounter them. They are longer-lived (like the Geolycosa from my previous post); females may live 2-3 years while males typically live a single season (Kaston, 1948). Both species build burrows, sometimes under rocks or logs, from which they emerge each night to hunt for prey. Both members of the genus have a pale yellow to yellow midline stripe on the carapace.

On iNaturalist, Tigrosa helluo is called the Wetland Giant Wolf Spider. As its common name suggests, it is associated with wetlands and lake edges though Kaston indicated it has been found in woodlands as well (1948). In this species, the coloration ranges from dull yellow to greenish brown (Kaston, 1948) but darker individuals do occur. The pale yellow midline extends from the anterior eyes all the way to the rear of the carapace (in most individuals). The femurs are typically dark or spotted but they lack the "tiger stripes" of T. aspersa. This species is known from 8 counties at this time from southern Minnesota north to Lake County along the Lake Superior shoreline. An example of a typical specimen can be found here: https://www.inaturalist.org/observations/122710979. A darker individual can be found here: https://www.inaturalist.org/observations/5280939.

On iNaturalist, Tigrosa aspersa is called the Woodland Giant Wolf Spider. It is the least known member of this genus in North America because it is the least encountered (Brady, 2012). This species is larger than T. helluo and was only recently added to the Minnesota spider list. The pale yellow midline is most pronounced at the anterior region of the carapace and fades toward the rear (Brady, 2012 indicates that it is only found in the ocular area, but firsthand experience suggests that trait may be variable). The femurs show pronounced "tiger stripes" of alternating, irregular black and pale yellow bands; this characteristic is absent in T. helluo. The burrow entrance may have a turret that incorporates straw or twigs (similar to Geolycosa) (Kaston, 1948). This species is only known from a single specimen found in Houston County which can be found here: https://www.inaturalist.org/observations/163305282.

Happy spidering!

Sources
Brady, Allen R. 2012. Nearctic species of the new wolf spider Tigrosa (Araneae: Lycosidae). Journal of Arachnology, 40 (2):182-208.

Kaston, B. J. 1948. Spiders of Connecticut. Bulletin of the Connecticut State Geological and Natural History Survey 70: 1-874.

Posted on May 27, 2023 03:40 PM by cheins1 cheins1 | 0 comments | Leave a comment

April 22, 2023

Geolycosa

Wolf spiders in the genus Geolycosa are commonly known as Burrowing Wolf Spiders. As their name implies, they spend much of their life in burrows, rarely leaving them. The relatively vertical burrows can be pretty long (170cm!) and the upper parts of the burrow are often reinforced with silk so the tunnel does not crumble inwards. Some species even have a turret that extends upward from the burrow entrance (see https://www.inaturalist.org/observations/119596857). These spiders are ambush hunters; they sit and wait near the entrance of their burrow for prey to stumble by and then rush out to grab their dinner. They mature in late summer, overwinter as adults and eggs are laid in the spring. Most species take two years to reach sexual maturity (Wallace, 1942).

Minnesota is blessed with three species of Geolycosa and since they rarely leave their burrows, very little is known about their distribution in the state.

G. missouriensis is known from 5 Minnesota counties from Kandiyohi and Hennepin north to Cass and Mille Lacs. This species prefers sandy soils with sparse vegetation, the debris of which is often incorporated into the shallow turret structure at the mouth of its burrow (Dondale & Redner, 1990). https://www.inaturalist.org/observations/135942978

G. turricola is only known from Ramsey County. It has a more easterly distribution and reaches the westernmost part of its range in Minnesota. As its name suggests, this species also has an elevated turret composed of sand, silk and vegetation at the mouth of its burrow. It also prefers sandy soils but has been found less sandy soils too. https://www.inaturalist.org/observations/142013793

G. wrighti is known from 6 Minnesota counties, primarily from Wabasha north into the Twin Cities but also from Lake of the Woods County. This species prefers bare, sandy areas and their burrows are heavily lined with silk but lack a turret (Dondale & Redner, 1990). It may be a species to look for when visiting a beach. https://www.inaturalist.org/observations/146937931

Much of the natural history information in this post was acquired from Dondale & Redner, 1990 except where noted otherwise.

•Dondale, C. D. & J. H. Redner. 1990. The insects and arachnids of Canada, Part 17. The wolf spiders, nurseryweb spiders, and lynx spiders of Canada and Alaska, Araneae: Lycosidae, Pisauridae, and Oxyopidae. Research Branch, Agriculture Canada, Publ. 1856: 1-383.

•Wallace, H. K. 1942. A revision of the burrowing spiders of the genus Geolycosa (Araneae: Lycosidae). American Midland Naturalist, 27: 1-62.

Posted on April 22, 2023 04:14 PM by cheins1 cheins1 | 0 comments | Leave a comment

March 17, 2023

Sergiolus

The genus Sergiolus possesses several colorful and/or boldly patterned species of ground spiders (Gnaphosidae). Like many members of this family, individuals are reclusive and are often found in the leaf litter, under stones, logs and rocks though males can sometimes be found out in the open as they seek mating opportunities with females. Like many of the other ground spiders, the tubular spinnerets (that do not taper at the tip) are often pronounced and are a good characteristic to look for.

Minnesota has records of six species of Sergiolus but like many of our Minnesota spiders, very little is known about their distribution in the state.

S. capulatus likely occurs statewide but is only known from nine counties currently. The carapace is orange-brown and the black abdomen has a pattern of white bands, one of which forms a white T-pattern that extends anteriorly from the white band immediately posterior. A good example can be seen here: https://www.inaturalist.org/observations/123980179.

S. montanus also likely occurs statewide and is known from 11 counties currently. Unlike S. capulatus, its coloration is limited to black and white. The carapace has whitish hairs that often cover the entire surface though sometimes they are limited to the median area. The abdomen has variable amount of white. Here are two individuals showing the variation extremes: 1) https://www.inaturalist.org/observations/97631821 and 2)https://www.inaturalist.org/observations/98674551.

S. tennesseensis is the only other species on iNaturalist that has been found in Minnesota (1 county). While similar to S. montanus in coloration, its pattern is much bolder and femurs are dark while the lower legs are pale. https://www.inaturalist.org/observations/122204696

The other species are known from 3 or less counties

S. bicolor is dark overall with a white band on the anterior of the abdomen that is broken in the middle. It is superficially very similar to S. montanus and juveniles of these two species are probably especially difficult to distinguish. There are historical records from Anoka and Hennepin Counties.

S. decoratus has an unmarked carapace but its abdomen is mostly white with median dark patches at the anterior and posterior of the abdomen but a pair of dark patches that are more lateral in their placement in between those. This species is only known from Jackson and Clay Counties.

S. ocellatus is more similar to S. capulatus in coloration. The carapace is orange-brown and the abdomen is dark with a white pattern upon it. This pattern consists of an anterior white band followed by a pair of isolated white spots, followed by another white band and one more white band at the posterior of the abdomen. It is known from Hennepin, Ramsey and Cass Counties.

Posted on March 17, 2023 05:23 PM by cheins1 cheins1 | 0 comments | Leave a comment

February 09, 2023

Genus Micaria

The genus Micaria consists of ant-like species that belongs to the ground spider family (Gnaphosidae). In appearance, they are more likely to be confused with the genus Castianeira in the family Corinnidae than they are with fellow ground spiders (they both belonged to the family Clubionidae at one point). Jumping spiders in the genus Tutelina and Synageles have some superficial similarities, but eye arrangement and behavior can quickly rule them out.

Members of this genus move quickly (bordering on frantic). Just think, "Fast-moving Ant" and you will have a good idea what to expect. Many species seem to prefer upland, dry habitats but I have found M. pulicaria running with Pardosa wolf spiders at the edge of a wetland. One of the characteristics of these spiders is the flat, iridescent scales that cover their abdomen and sometimes the carapace. It can give them a very bright (and sometimes colorful) appearance.

In Minnesota there are 5 species of Micaria that are known to occur in the state and an additional 3 species that are listed as hypothetical. They are poorly represented in collections and very little is known about their distribution in the state.

M. pulicaria has the best known distribution in the state (12 counties). It is known from Freeborn and Blue Earth Counties in the south to Koochiching and Roseau Counties in the north which suggests it may be found statewide. https://www.inaturalist.org/observations/25522283

M. longipes may well occur across the state but is only known from Blue Earth, Wabasha, Ramsey, Itasca and St. Louis Counties. https://www.inaturalist.org/observations/92601891

M. gertschi is known from Blue Earth, Hennepin, Ramsey, Renville, and Rock Counties. I have only found specimens in a rock garden on the campus of Bethany Lutheran College. https://www.inaturalist.org/observations/5219349

M. riggsi is only known from Clay County.

M. rossica is only known from Itasca County.

The three species that are listed as hypothetical are: M. aenea, M. emertoni, and M. longispina.

Keep an eye out for these spiders in the coming summer.

Happy Spidering!

Posted on February 09, 2023 10:54 PM by cheins1 cheins1 | 2 comments | Leave a comment

December 24, 2022

Lynx Spiders

24 December 2022

Lynx spiders (Oxyopidae) are some of the most interesting spiders to watch. They are active hunters with thin, spiny legs and forward pointing eyes. They move quickly and actively hop from leaf to leaf as they go. Their behavior is very similar to the jumping spiders.

Minnesota is home to two lynx spiders in the genus Oxyopes:

O. salticus (Striped Lynx Spider) is a common denizen of prairies, grasslands and other open habitats. Females have lots of stripes with dark vertical stripes on the face and short, dark stripes on the sides of the carapace. Mature females also have white longitudinal stripes on the dorsal surface of the carapace. Mature males are glossy with orangish carapace and a dark greenish abdomen.
https://www.inaturalist.org/observations/6746367
https://www.inaturalist.org/observations/143314868

O. scalaris (Western Lynx Spider) is more likely to be found at forest edges. Its pattern is not as bold as that of the Striped Lynx. It has a broad pale median area on the carapace and abdomen. On the abdomen there are a couple of white lateral marks that extend toward the sides. https://www.inaturalist.org/observations/123439538

One final note: The Green Lynx Spider (Peucetia viridans) is an accidental species that has occurred in the state. It typically arrives with plants shipped to greenhouses and is unlikely to occur in native habitats.

Posted on December 24, 2022 09:08 PM by cheins1 cheins1 | 1 comment | Leave a comment

November 16, 2022

Steatoda

Now that we have arrived at "indoor season" for spiders, perhaps it is time to look at one of the genera that is commonly found inside of our buildings. The genus Steatoda belongs to the family Theridiidae (the cobweb spiders). These spiders construct a tangle of webs that are much more disorderly than the beautiful webs of the orbweavers discussed in earlier posts. Such webs are often found in protected sites such as tree hollows, under rocks, and the interior corners of our homes. The spider is often hidden within the tangle of threads or remains very still at it perimeter. If the spider feels threatened, it will drop and remain still on the ground, relying on its camouflaged body to remain hidden.

The genus Steatoda in Minnesota is represented by three species:

S. borealis (Northern Combfoot) is found statewide. This species is a dark mahogany brown overall with a white band on the anterior of the abdomen. In some individuals, an additional white median stripe on the anterior of the abdomen is also present and is often connected to the white band. This is more pronounced in females than males. This species may be found inside buildings but is also commonly found under logs and rocks.

S. triangulosa (Triangulate Combfoot) is a non-native species that is more common inside buildings than S. borealis. Because of this, this species is also likely to be found statewide though it is not known from the northern third of the state. Their name comes from the pale pattern on the brownish abdomen.

S. albomaculata (White-spotted False Widow) is the least known member of the genus in Minnesota but probably also occurs statewide. I have most often found them under rocks in open habitats. As the common name suggests, they have white spots on their abdomen and are somewhat similar to S. triangulosa.

S. borealis: https://www.inaturalist.org/observations/90091835
S. triangulosa: https://www.inaturalist.org/observations/69336258
S. albomaculata: https://www.inaturalist.org/observations/98741973

Happy spidering!

Posted on November 16, 2022 09:00 PM by cheins1 cheins1 | 0 comments | Leave a comment

October 15, 2022

Micrathena

15 October 2022

The layer of ice on top of my birdbath this morning tells me that we finally had a good frost overnight. With temperatures dropping across the state, the number of spider observations added daily to iNaturalist has also precipitously declined. So go the seasons of Minnesota. I'm enjoying writing about some of our Minnesota spider genera and thought I would stick with the Araneidae for another post.

The orbweaver genus Micrathena is found throughout the temperate and tropical Americas with its highest species diversity occurring in the tropical forests much further south. Many of the members of this genus have horn-like spines and spikes on their abdomen that may help break up their outline and make them less visible to their predators. Some of them have white and black coloration which can make them resemble bird poop and may also help them to hide in plain sight. After all, who eats that?

Minnesota is home to three members of this genus. These small orbweavers are most often found in wooded understories in the southern two-thirds of the state. Males are smaller and less conspicuously colored than the females.

M. mitrata or White Micrathena is our most common species in Minnesota. As its name implies, the female has a white abdomen with prominent spines on the posterior of its abdomen. It has been found from Pine County west to Stearns and Redwood Counties and southward within the Mississippi watershed. Ironically, the literature did not have any published records of this species in Minnesota when I first began my work on spiders back in 2009.

M. gracilis or Spined Micrathena has been most commonly reported from the southeast corner of the state (Wabasha to Houston Counties) but there is a record from Blue Earth County as well. Females of this species also have a white abdomen but it has prominent spines on both the sides and posterior of the abdomen.

M. sagittata or Arrow-shaped Micrathena is our rarest member of the genus. It has a more southern distribution and therefore is most likely to occur in the southeastern part of the state, particularly the Mississippi River Valley. This females of this species have a yellow abdomen and the spines at the posterior part of the abdomen are quite long.

White Micrathena: https://www.inaturalist.org/observations/92518296
Spined Micrathena: https://www.inaturalist.org/observations/138871756
Arrow-shaped Micrathena: https://www.inaturalist.org/observations/93322230

Happy spidering!

Posted on October 15, 2022 07:05 PM by cheins1 cheins1 | 2 comments | Leave a comment