7. elokuuta 2022

Araneus

6 August 2022

Orb-weavers (members of the family Araneidae) are some of the most conspicuous members of Minnesota's spider fauna. Their target-shaped webs are easy to see (or walk into) since they span open air space between plants, trees and other objects. The behavior of sitting in the center of their web or in adjacent retreats may make these spiders more noticeable as well.

Eighteen Araneidae genera have been documented in Minnesota. Most genera are represented by only a few species. For example, there is one species of Acanthepeira, two species of Argiope, three species of Larinioides, etc.. Then there's Araneus.

The genus Araneus is diverse in size and shape and represented by 14 species in Minnesota. A majority of the species are larger , particularly the females but some members of the genus are relatively small in comparison. Many species have conical "humps" on the anterior of the abdomen but that is not true of all species.

Known distributions for the different species vary. Some we know pretty well but most are poorly known.

A. bicentenarius is known from Clearwater to Cook Counties and south to Ramsey County. It is probably found in forested ecosystems which makes it unlikely in the west/southwest.

A. cingulatus is only known from a single record from Hennepin County.

A. corticarius is only known from Clearwater, Hubbard and Carlton Counties.

A. diadematus is a non-native species found primarily in the Twin Cities and Rochester areas but it is spreading slowly (see earlier journal post).

A. gemmoides is widespread with records throughout the southern 2/3 of the state.

A. groenlandicola is a bog specialist and likely to be found in the extreme northern part of the state (no county records yet but known from the state).

A. guttulatus is only known from Lake of the Woods and Lincoln Counties.

A. iviei is known from Lake of the Woods to Cook County but there is a surprising record from Washington County too.

A. marmoreus is widespread in the state and likely has a statewide distribution (though poorly known from southwestern counties currently).

A. nordmanni is known from Pope to Cook Counties and is most likely in the northern half of the state.

A. pratensisis known from Houston to Roseau Counties but prefers grasslands and therefore is likely to occur in the prairies and aspen parkland ecosystems in the state.

A. saevus is known from around the state but its distribution is still poorly understood.

A. thaddeus is primarily known from the eastern part of the state from Pine County south to Winona County.

A. trifolium is found statewide.

Keep an eye out for those Araneus!

Lähetetty 7. elokuuta 2022 04:33 käyttäjältä cheins1 cheins1 | 0 kommenttia | Jätä kommentti

27. kesäkuuta 2022

Something New

I just wanted to take a moment to thank all of you who have contributed your observations to the Spiders of Minnesota Project and thereby have increased our knowledge of Minnesota's spider fauna. I expect that we will surpass 9,000 observations for the project in the next couple of days.

A number of your observations have been significant in that they have provided new information about Minnesota spiders. Many observations have represented new county records and there have even been a few new state records. With a list of 519 species known from Minnesota (as of 16 June 2022), finding a state record is particularly difficult, especially when you are not looking for them intentionally.

Here's a few of those state records that iNaturalist observers have added to the Minnesota spider list:

Lähetetty 27. kesäkuuta 2022 15:38 käyttäjältä cheins1 cheins1 | 0 kommenttia | Jätä kommentti

24. toukokuuta 2022

Warblers and Jumpers

I've discovered over the years that many of my fellow entomologists and araneologists are also birdwatchers. Birds come in so many shapes and sizes, with muted to gaudy colors and a diversity of bird songs and call notes. Throw in annual migrations and other fascinating behaviors and you have the perfect organism to draw someone into a lifelong pursuit of learning. Most birdwatchers can trace back to the moment when they became a birdwatcher and not just a casual observer of birds. For me and many other birdwatchers, we point to our first brush with warblers in the month of May. For me, that brush occurred when I was only 14 and I noticed some little birds flitting about in the elm in my backyard. The first warbler I looked at was a Prothonotary; the second was a Blackburnian. Each little bird I looked at that morning with my dad's binoculars was different and each one was prettier than the next. I was hooked.

I would say a similar thing happened to me to get me interested in spiders. I had decided to teach about animal communities and had selected spiders as my model organisms. I was naïve to think that I knew something about them and that spiders did not have the overwhelming diversity of insects. The plan was to have students collect spiders from the sides of various buildings and compare the communities of buildings adjacent to woodlands with buildings further away from the woodlands. To prepare myself and make sure I knew what we would encounter, I began capturing spiders off of the buildings, taking their picture under a microscope and returning them to their habitat.

One of the first spiders I encountered was the common, synanthropic Zebra Jumper (Salticus scenicus) with its bold black and white stripes. I had known this jumper since I was a little kid and was unaware of any other species. But then I turned a corner and found another black and white jumper with a completely different pattern. I would go on to learn it was a Flea Jumper (Naphrys pulex). Asian Wall Jumper (Attulus fasciger) was next and then I had my Prothonotary moment. A very fast moving jumping spider that ran and hid behind the siding when I first saw it. It was larger and more colorful and it would take several efforts to finally catch it. It was a female Dimorphic Jumper (Maevia inclemens) with bold red chevrons on her abdomen and reddish eyes. I was hooked.

With over 70 species of jumping spiders recorded in Minnesota, Salticidae is still one of my favorite families to study. I love to look at the green metallic chelicerae of the large and curious Phidippus jumpers or the leg ornamentation on male Habronattus. Some jumpers are so tiny as to be overlooked (Talavera minuta/Neon nelli) while others hide in plain sight as ant mimics (Synemosyna/Synageles/Peckhamia). Still others are just as gaudy as warblers (Pelegrina flavipes, Hentzia mitrata, Paradamoetas fontanus).

By the way, as a result of extensive jumping spider surveys in Minnesota, the jumping spider, Tutelina formicaria, is listed as state threatened (the only spider listed as such in Minnesota). It is an ant mimic and is only known to occur in Anoka County. There are other species listed as species of special concern and you can find them listed in the DNR's rare species guide here: http://files.dnr.state.mn.us/natural_resources/ets/endlist.pdf.

Keep an eye out for those jumpers!

Lähetetty 24. toukokuuta 2022 15:04 käyttäjältä cheins1 cheins1 | 0 kommenttia | Jätä kommentti

1. huhtikuuta 2022

Let's talk Tibellus!

In Minnesota there are three species belonging to the genus Tibellus that are known to occur (and likely occur statewide): T. oblongus, T. maritimus and the rarer T. duttoni. There is also a fourth species that is hypothetical in its occurrence in the state and believed to most likely occur in the northern half: T. asiaticus . They all belong to the family Philodromidae and are commonly called running crab spiders and members of the genus Tibellus are often called the slender running crab spiders. As their name suggests, these spiders are slimmer and very quick on their feet. They do not spin a web like orbweavers but rather are active hunters.

Members of this genus are often found in grassland habitats and that makes them fairly easy to find, especially if you use a net to sweep through the grass. Their coloration and pattern enable them to blend in with stalks of dry grass and they often perch vertically on stems (and hide behind them like a woodpeckers hide behind the trunks of trees).

I have not been able to determine what underlying environmental factors determine which species is likely to occur in a given grassland. I have found that T. maritimus and T. oblongus are most common and sometimes co-occur in the same grassland (though often it is one or the other). I've also found the three common species in a single grassland in south-central Minnesota which was surprising because I would expect competition to limit how many species can occur in a single area since they occupy the same niche.

Identification of these spiders is a little tricky. Most taxonomic keys begin by asking how many pairs of macrosetae (thick hairs) are on the ventral side of the first leg's tibia. Most of Minnesota's species have 3 pairs but T. duttoni has 4 pairs. If the macrosetae are not visible in a picture (more than likely), one could look for a pair of dark spots on the dorsal surface on the rear third of the abdomen. T. maritimus lacks these spots, but the other three species all have them. Most Tibellus with a pair of dark spots on the abdomen are likely T. oblongus due to this species' broad distribution and how commonly it occurs. However, examination of the first leg's tibia or reproductive structures (palp/epigynum) are really necessary in order to rule out the other two species which also show the paired spots.

Happy spidering!

Lähetetty 1. huhtikuuta 2022 19:59 käyttäjältä cheins1 cheins1 | 0 kommenttia | Jätä kommentti

23. helmikuuta 2022

Signs of Spring?

23 February 2022

While the most recent cold front has brought temperatures down below zero again and with it a fresh blanket of snow, I cannot help but think of spring. Just a couple of days ago it was nearly 50 degrees in Mankato and that warm day woke up a few Boxelder Bugs in my home and reminded me that when the prey get moving, so do the spiders.

Since spider body temperature depends on the temperature of their surrounding environment, their bodies do not move as quickly in February and March as they do in May and June. That does not keep them from moving and on sunny days with little wind, you may be able to find spiders out looking for food, even walking across the snow. Fortunately, their prey is typically moving about at the same speed this time of the year.

Spiders in my home and in my building at work are also starting to move around a little. My daughter brought me a Steatoda triangulosa she found in the house the other day and I scared up several cellar spiders (including an adult male ready for breeding) and an Asian Wall Jumper when I was cleaning the greenhouse the other day. I also found a dead Woodlouse Hunter (Dysdera crocata) in the hallway that was pretty dessicated.

Enjoy the snow melting and the birds singing, but keep an eye out for those waking spiders too!

Happy spidering!

Lähetetty 23. helmikuuta 2022 16:58 käyttäjältä cheins1 cheins1 | 0 kommenttia | Jätä kommentti

21. syyskuuta 2021

The Erigoninae

21 September 2021

The Erigoninae or Dwarf Spiders are, as their common name suggests, tiny (on iNaturalist, they are referred to as Money Spiders). For iNaturalist observations, it is a rare day when such specimens can be identified to species from mere photographs of the animal in its natural setting. They are just too small and there are just too many similar species. Most require microscopic examination or even dissection to identify to species, and even then there is no guarantee.

If you find one, you hope it is a male. The Spiders of North America manual for identifying spiders to the genus level only has an identification key for males. There is no such thing for the females. If you have a female, you'll have to search several scientific papers for illustrations or point your internet browser to repositories of photographs of female reproductive parts. And yet...this group of spiders is probably the one that I get most excited about finding. Our knowledge of the distribution of these diminutive spiders is limited and I have found several dwarves that represented new records for Minnesota and a significant expansion of their known range.

There are several species of dwarf spiders that mature in fall and it is an active ballooning period for them. I was reminded of that again a couple of weeks ago when I was sitting at a picnic table with my wife and a male Erigoninae landed on the table in front of me. Unfortunately, he was there only momentarily and blew away again before I could get a jar to put him in. The state's first record of Islandiana flaveola arrived in similar fashion, landing on one of my sharp-eyed students who noticed it crawling on her as she walked to class. She knew that I might find it valuable and guarded it until she got to the lab and we could capture it in a jar.

As you enjoy the cooler weather of the fall, keep an eye out for our smallest spiders and snap a few pictures if you get a chance.

Lähetetty 21. syyskuuta 2021 20:35 käyttäjältä cheins1 cheins1 | 0 kommenttia | Jätä kommentti

9. elokuuta 2021

August Agelenopsis

9 August 2021

Tis the season for Agelenopsis, the grass spiders. As their name implies, they are often found in grassy habitats where they make a sheet-like web with a funnel-like retreat in which the spider hides. The web itself is not sticky like it is in orbweavers. The spider waits in its retreat for a prey item to land on the sheet. The slightest vibration of the sheet acts like a starting gun at a track meet and the spider rushes out to try and grab the prey. You can see this behavior by taking a grass blade and just lightly touch the web of one of these spiders.

Grass spiders may just as well be named the gutter spiders or the siding spiders. I often find their webs behind the downspout on the corner of my house or extending outward from a 90-degree corner, their retreat tucked back into the edge of the siding. My front porch has several Agelenopsis webs because the spiders are taking advantage of the abundant insect prey that are attracted to the porch light.

Minnesota has records of seven species of grass spiders and they all look very much alike. The most common species (from my experience) is Agelenopsis potteri or Potter's Grass Spider. Distinguishing between the different species is very difficult (particularly in the females) and dissection of the genitalia is often required (and even then it can be tricky). Most my IDs are left at genus.

More information on this genus can be found on BugGuide here: https://bugguide.net/node/view/2001.

Lähetetty 9. elokuuta 2021 15:14 käyttäjältä cheins1 cheins1 | 4 kommenttia | Jätä kommentti

10. heinäkuuta 2021

The Diadem Spider

10 July 2021

As we head into the heart and heat of a Minnesota summer, it is time for our larger orbweavers to reach maturity. I've seen several observations of Araneus nordmanni, Araneus bicentenarius, and Argiope aurantia start to pop up here on iNaturalist.

One of the distinctive species of Araneus that we have in Minnesota is the non-native A. diadematus which is native to Europe. The common name assigned to this species here on iNaturalist is the Cross Spider but I prefer the name of Diadem Spider which eliminates some confusion with another species that is sometimes called a cross spider: Neoscona crucifera. This native species has cross right in its specific epithet: crucifera. Here on iNaturalist that species is called the Spotted Orbweaver which I typically think of as a more general term for members of that genus. I guess this is why we scientists prefer the Latin! :)

Araneus diadematus is not very common yet in Minnesota. Most observations have been out of the greater metro area of the Twin Cities but there have been several observations out of the Rochester area as well. There are also single records from Dodge and Freeborn Counties in the last year which suggests this species is slowly expanding its range. Keep an eye out for this species in their typical orb webs as you hunt for spiders in the coming months.

There is some great information about identifying this species on BugGuide (my favorite online field guide): https://bugguide.net/node/view/3376.

Lähetetty 10. heinäkuuta 2021 14:58 käyttäjältä cheins1 cheins1 | 0 kommenttia | Jätä kommentti

11. kesäkuuta 2021

The Meshweavers

11 June 2021

If I had to name one family that is most frequently misidentified or leaves most people mystified, it would have to be the meshweavers in the family Dictynidae. I have seen them identified as Linyphiidae, Araneidae, Gnaphosidae, Theridiidae and many of the other families. Most of the IDs that I offer are left at the family level because this is one of the trickiest families to identify to species. Many of the species are similar in appearance and require microscopic examination to see the distinguishing characteristics. Even then, their diminutive size makes them difficult to dissect and after dissection I have been left scratching my head on more than a few. Ralph Chamberlin and Willis Gertsch (one-time U of M Professor) wrote their seminal work on identifying members of this family back in 1958, making the most reliable literature over 60 years old. If I had another lifetime, maybe I'd work on an update.

Finding dictynids is fairly easy if you know what to look for. In prairies and grasslands, I often find them by looking carefully at plants. They make a chaotic web near the shoot tips (particularly on woody plants) and the tiny spider is normally concealed within. Often I just collect the whole tip of the plant and get the spider out when I get back to the lab.

In broadleaf forests in early summer, Emblyna sublata is fairly easy to find. Webs appear as tangles within curled up leaves. Females come in two color morphs and males look completely different from either of them just to add to the confusion. The chelicerae of the male are pretty cool to look at under a microscope because they have a bow-legged look with a gap in the middle.

Dark female: https://bugguide.net/node/view/1670861/bgimage
Light female: https://bugguide.net/node/view/1051738/bgimage
Male: https://bugguide.net/node/view/399568/bgimage
Male chelicerae: https://bugguide.net/node/view/891375/bgimage

I hope you find more meshweavers this summer in your spidering. Just don't expect me to identify them to species! :)

Lähetetty 11. kesäkuuta 2021 15:23 käyttäjältä cheins1 cheins1 | 1 kommentti | Jätä kommentti

7. toukokuuta 2021

Pardosa Party

7 May 2021

If you are walking through a grassland or along a wetland edge at this time of year, a careful study of the ground immediately in front of you will reveal many spiders running along the ground, darting in and out of the matted grass from last year as they flee before you. In my experience, most of these will be wolf spiders and the predominant genus represented in this fauna will be the genus Pardosa which are commonly called the Thin-legged Wolf Spiders.

I would consider members of this genus to be the smaller of the medium-sized wolf spiders. Wolf spiders in Pirata and Piratula are really the only ones smaller. As their common name implies, they have thin legs, often with erect spines on them. Their coloration is typically a combination of gray, brown and black. Males are often more strikingly patterned than females and have the swollen pedipalps typical of male spiders. There are a few males that are relatively distinctive (P. hyperborea, P. saxatilis), but very few females (P. distincta).

There are 16 species of Pardosa that are known to occur in Minnesota and an additional 4 species that may occur but for which there are no records yet (yet!). Unfortunately, many of these spiders seem to overlap in their habitat preferences and are very similar in appearance. It is common for me to offer only Pardosa as my best identification on iNaturalist. Three of the species I commonly encounter even got alliterative names which crosses me up even more. I refer to them as the 3Ms (P. milvina, P. moesta, P. modica). Distinguishing them from one another often requires microscopic examination of reproductive structures which isn't for everyone.

I hope this doesn't dissuade you from taking pictures of these spiders. They are subtle beauties and definitely represent challenging photography subjects since they are fast movers. Many rely on their cryptic coloration to hide and may run a short distance and then freeze. That will be your chance to snap a picture or two before they run off again.

Happy spidering in the month of May!

Lähetetty 7. toukokuuta 2021 13:25 käyttäjältä cheins1 cheins1 | 4 kommenttia | Jätä kommentti