In search of the elusive Argiope

This morning, Lori Spears, Ben Kuethe and I went to a field located not far from Thatcher, a small town west of Tremonton. Someone had told Lori that there had been large amounts of Argiopes last year in this field in the late summer. Although this genus in the family Araneidae can be quite common in the right type of habitat, I had not seen it yet in the U.S. We followed the instructions to get there, eager to find some big Argiopes.

The field consisted mostly of grasses, thistles, and a few small shrubs:

We walked around for quite a while without seeing any spiders at all, until we came across a couple of large orb webs. The occupants turned out to be Aculepeira spiders, which are in the same family as Argiope. These Aculepeira were big and appeared to be well fed, as suggested by the prey items caught in their webs. The abdomen of Aculepeira is typically egg-shaped, widest anteriorly, and has a dorsal longitudinal lobed band.

Only two or three species of Aculepeira can be found in North America. According to Levi 's publication The orb weaver genera Metepeira, Kaira and Aculepeira north of Mexico (Araneae, Araneidae), the species we found was probably A. packardi, as suggested by the posteriorly directed lobes on the back of the abdomen. I have collected this species at my field sites in Logan Canyon, but I had not seen any as big as the ones here. Adult A. packardi females build a new web every night and actively remove prey caught during the day.

Aculepeira  resting on thistle 

Aculepeira sitting in the hub of her web with a prey item

Aculepeira working on a large prey item

Aculepeira has a typical median ventral white streak, as seen in the picture below:

As we were discussing why we did not find any Argiopes yet, Lori found a small Argiope trifasciata in its web, not very far above the ground! This was the only one we were able to find, but it was a pretty spider that made our trip worthwhile.

Lori finds an Argiope

Argiopes sit on the web with their head facing downwards, and their legs are often held in pairs. Argiope trifasciata is also known as the Banded Garden Spider. The back of its abdomen is a silvery/pale yellow background, with several horizontal black stripes, and the legs are striped. We think our spider was immature, as it was relatively small and had a mostly white dorsal surface.

I have read that Argiope trifasciata prefers to orient its web along an east-to-west axis, with its abdomen facing south. Given that the underside of A. trifasciata is mostly black, the orientation of the spider is supposed to maximize solar radiation and heat gain, which is an important consideration for spiders that are active late in the year.

Argiope trifasciata

The dark underside of A.trifasciata

We decided to return to this site in about a month, in hopes of finding adult Argiopes.

Dreaming about Colombia, part 1: El Paujil reserve

In 2008 I went to Colombia to visit my family in Bogota and to spend some time in a couple of reserves that belong to the Fundacion ProAves, an NGO dedicated to the conservation of birds and their habitats. I had such an amazing time there that lately I have been longing to go back. While I wait for my next colombian adventure, I decided to post some spider pictures from that trip. The amount and diversity of spiders in these reserves was staggering, making these places a dreamland for arachnologists. There were spiders and spider webs everywhere!

El Paujil is a  reserve dominated by rainforest, located in the departments of Santander and Boyaca. I spent a few days there, dedicating all my time to observing all the plants and animals I could find. I found it exciting to think that there are probably many undescribed species in this part of the world. We spent nights in a nice wooden cabin in the reserve. One of the first spiders I found was the one below, behind the cabin:

 

At lunch time, I noticed this small Argiope (family Araneidae) near the base of a tree. In North America, these spiders are known as Garden Spiders. Argiopes build orbwebs with a special silk structure in the middle called a stabilimentum (see picture below). The pattern of the stabilimentum varies across species, and the role of this structure is subject to debate.

Argiope sitting on the stabilimentum of it web

I also noticed this pretty jumping spider, which was wandering on a wooden post close to our lunch area:

 

My last find at lunch time was this araneid spider, which I found hidden in a rolled-up leaf. The silk structure at the tip of the leaf had called my attention. This spider had a roughly triangular shape, with several humps on the posterior part of her abdomen.

 

Along one of the trails in the reserve, I found my first Micrathena spider. I was so excited to find it but a little frustrated because I felt a little rushed as the rest of the group kept on walking. In addition, my camera lens had gathered condensation due to high humidity levels. I was able to take one acceptable picture. Micrathena spiders are araneids (they build orbwebs) that have a typical arrow shape due to the spiny projections on their abdomen.

On the side of a more open trail, I noticed many spiders like the ones below. Their translucent legs were hard to notice against the background vegetation. I think these were oxyopids, a family also known as the Lynx Spiders, due to their hunting strategy which consists in jumping and running after their prey, and their relatively good eyesight. I was able to take pictures of some spiders that had caught a prey item, including a fat caterpillar. Oxyopids have spiny legs, as seen in these pictures.

A red jumping spider caught my attention along another trail. It was very active and curious, and jumped on my camera a couple of times to investigate it. I had to place him back on the plant to take more pictures.

I found this other jumping spider in a very shaded area, where the canopy was dense:

One orbweb along the trail had a pretty spiral shaped stabilimentum. In an attempt to find out who had built this web without scaring the spider away, I carefully placed my camera behind the web and took a picture at random, hoping that it would be in focus. My strategy worked and revealed that there indeed was a spider hiding under the stabilimentum, but I can't tell what spider this was.

One section of the trail was in close proximity to a river. Upon inspection of a big log, I noticed this beautiful orbweb spider. I had never seen this species before, but I think it may be a tetragnath spider of the genus Leucauge. Members of this genus have a cluster of long trichobothria (these are hair-like structures that detect vibrations) prolaterally at the base of their femurs on their fourth legs. These trichobothria are noticeable in the picture below. The second picture shows the orbweb, with relatively few radii and a "hole" in the center, which are typical tetragnath web characteristics.

Also by the river, we found this Pisaurid spider (also known as Fishing Spider) resting on a small tree trunk. These spiders are able to stay underwater for a few moments. They feed mainly on aquatic invertebrates and sometimes on small fish.

At night time, my cousin Esteban, Ryan and I went out exploring not too far from our cabin. We were rewarded with a small tarantula, which was wandering about right next to the steps that led to our cabin.  Tarantulas have fangs that point straight down, whereas other spiders have fangs that cross each other.

Meanwhile, back in France..

My mom sent me a couple of pictures of a spider she found in our house, in Brittany, France. This spider, which belongs to the family Pholcidae (cellar spiders), genus Pholcus, brings back memories from home, as I remember seeing these when I was younger. I remember throwing small paper balls in their webs to see if the spider would mistaken them for prey items. Instead, the spider would shake and vibrate in its web. I later found out that this shaking is a defense mechanism which makes the spider look blurry and therefore more difficult to catch.

This spider was surrounded by her offspring, which first looked like small dots in her web:

The second picture shows the same spider and her young, now a little older:

Pholcids are long-legged spiders that hang upside down in tangle webs, which they typically build in dark areas (cellars, caves), but sometimes also in warm areas inside houses.

Payette river rafting trip

My friends and I went to Idaho for a few days of great rafting on the Payette river. We stayed at a nice campsite not far from Crouch, a small town that had the craziest 4th of July fireworks I had ever seen. Our campsite was located by the river and had enough trees to provide shade...and interesting spider habitat. I searched for spiders a couple of times between our rafting adventures.

 View of the river from our campsite

My first find was this dictynid spider, which did not look like the dictynid species at my field sites in Logan Canyon (Utah). I had to gently poke her out of her tangle web to get a better look.

Close to the river, I noticed a male linyphiid spider in a sagebrush shrub. This spider was hanging upside down in its sheet-like web. When prey get caught in the web, linyphiid spiders bite them through the web while remaining upside down.

Anneli and Andy found this spider on the ground by our kitchen area. I have not seen this very cryptic looking species before, but I would guess that it is a philodromid spider, as it looks like a darker version of Philodromus histrio, a species common on sagebrush in Northern Utah. Philodromids are wandering spiders that do not rely on webs to catch prey. This family resembles the true crab spiders (Thomisidae) but philodromids have legs that are subequal in size whereas thomisids have third and fourth legs that are shorter than the first two pairs of legs.

One night, as we were chatting by the campfire, we noticed a small arthropod running around by our feet. Upon closer inspection, it turned out to be a solpugid!! Solpugids are also known as camel spiders but they are not spiders- they are a closely related order of arachnids. I was very surprised and excited to see one here, because I thought they were only found in desert areas. I guess that's not the case! Solpugids are typically nocturnal predators that use their impressive chelicerae to macerate their arthropod prey. I have heard that very little is known about solpugids because they are not easy find and difficult to keep in captivity. Perhaps this individual was hunting for arthopods that had been attracted to our campfire.

Solpugid hunting next to our campfire

That night I went to bed a little after midnight. As I was starting to fall asleep in my tent, I felt something walking on my arm. I turned on my headlamp and saw something hop straight onto the light! It turned out be a Phidippus jumping spider. I took a quick picture of it, let it out of the tent and went back to sleep. Jumping spiders are diurnal predators, but it has been shown that they sometimes use artificial light to hunt at night. This paper by Frank (2009) has some information on the subject:

Frank KD (2009) Exploitation of artificial light at night by a diurnal jumping spider. Peckhamia 78.1:1-3
http://peckhamia.com/peckhamia/PECKHAMIA%2078.1.pdf

Phidippus attracted to my headlamp. Picture taken after midnight.

House spiders

Sometimes one doesn't need to go far to find spiders. Some spiders are quite happy inside houses (especially if you don't clean things too often). Our house is of course very clean, but once in a while we get some neat spiders. Today I will focus on a particular microhabitat: the windows in the south-west corner of our house.

 

While I was eating breakfast, I noticed on the wall above the window a big Phidippus jumping spider. This one is probably Phidippus audax (a.k.a. the Daring Jumping Spider), a black species with abdominal spots  that are white in adults and sometimes orange in immature individuals. For some reason, I have never seen this species in the mountains, where I do my field work-I have only seen it down in the valley. The only Phidippus I have seen in the mountains is P. johnsoni.  

Phidippus (prob. audax)

I found a second jumping spider by the window, a very small immature Platycryptus. Spiders in this genus have a mottled pattern on the abdomen and a flat body that allows them to hide in tight places. I have often seen these spiders wandering outside on the house walls. 

 Platycryptus jumping spider

Perhaps jumping spiders favor window areas as hunting grounds inside houses because they are diurnal spiders that rely on their excellent vision to find prey.