Palm warblers eat insects from spiders’ webs


This video from the USA says about itself:

9 January 2017

Several Palm Warblers hunt for insects in spiders‘ webs in the morning – just like going to the grocery store! The spiders do all the hard work and the Warblers wisely reap some rewards. This behavior has apparently not been too well documented on video, although there is a technical name for this that I just learned – Kleptoparasitism (a form of feeding in which one animal takes prey or other food from another that has caught, collected, or otherwise prepared the food, including stored food). Always something new to learn by observing Nature!

Here is a link to a short scientific paper on the subject.

Insects, the biggest migration


This video says about itself:

Charles Anderson discovers dragonflies that cross oceans

17 December 2009

While living and working as a marine biologist in Maldives, Charles Anderson noticed sudden explosions of dragonflies at certain times of year. He explains how he carefully tracked the path of a plain, little dragonfly called the globe skimmer, only to discover that it had the longest migratory journey of any insect in the world.

From Science News:

Long-ignored, high-flying arthropods could make up largest land migrations

Each year, 3.5 trillion aphids, moths, flies and their kin fly over southern United Kingdom

By Susan Milius

2:46pm, December 22, 2016

Forget honking Vs of geese or gathering herds of wildebeests. The biggest yearly mass movements of land animals may be the largely overlooked flights of aphids, moths, beetles, flies, spiders and their kin.

About 3.5 trillion arthropods fly or windsurf over the southern United Kingdom annually, researchers say after analyzing a decade of data from special entomological radar and net sweeps. The larger species in the study tended to flow in a consistent direction, suggesting that more species may have specialized biology for seasonal migrations than scientists realized, says study coauthor Jason Chapman, now at the University of Exeter in Penryn, England.

The creatures detected in the study may be little, but they add up to roughly 3,200 metric tons of animal weight, Chapman and colleagues report in the Dec. 23 Science. That’s 7.7 times the tonnage of U.K. songbirds migrating to Africa and equivalent to about 20,000 (flying) reindeer.

These are “huge flows of biomass and nutrients,” Chapman says. “One of the things we hope to achieve in this work is to convince people who are studying terrestrial ecosystems that they cannot ignore what’s happening in the skies above them.”

Biologist Martin Wikelski of the Max Planck Institute for Ornithology in Radolfzell, Germany, who wasn’t part of the study, calls these migrants “aerial plankton.” It’s a reference to the much-studied tiny sea creatures whose movements and blooms power oceanic food webs. Understanding insect migrations and abundances is crucial for figuring out food webs on land, including those that link insects and birds. That’s “particularly important nowadays as we are starting to lose many of our songbirds,” he says.

The word migration applied to arthropod movements doesn’t mean one animal’s roundtrip, Chapman says. Instead, the term describes leaving the home range and undertaking a sustained journey, maybe cued by seasons changing or food dwindling. A return trip, if there is one, could be the job of a future generation.

The migrants he studied, traveling at least 150 meters aboveground, aren’t just accidentally blowing in the wind, he says. Many of the tiniest — aphids and such that weigh less than 10 milligrams — take specific measures to start their journey, such as trekking to the top of a plant to catch a gust. Juvenile spiders stand on tiptoe reeling out silk until a breeze tugs a strand, and them, into the air. “They only do this when wind conditions will enable them to be caught and taken up; otherwise, it’s a terrible waste of silk,” Chapman says. Some caterpillars also spin silk to travel, and mites, with neither wings nor silk, can surf themselves into a good breeze.

The basic idea that a lot of arthropods migrate overhead is “absolutely not” a surprise to behavioral and evolutionary biologist Hugh Dingle of the University of California, Davis. He says so not dismissively, but joyously: “Now we have really good data.”

This smallest class of migrants, sampled with nets suspended from a big balloon, makes up more than 99 percent of the individual arthropods and about 80 percent of the total mass. They didn’t show an overall trend in flight direction. But radar techniques refined at Rothamsted Research in Harpenden, England, showed distinct seasonal patterns in direction for medium-sized and larger insects.

“That’s the big surprise for us,” Chapman says. “We assumed that those flows would just be determined by the wind.” But medium-sized and large insects such as lacewings and moths overall tended to head northward from May through June regardless of typical wind direction. And in August and September, they tended southward. “Lots of insects we didn’t think capable of this are clearly doing it,” he says.

Managing such a feat takes specialized biology for directed, seasonal migrations. Many of these arthropods must have some form of built-in compass plus a preferred direction and the genetics that change that preference as they or their offspring make the return migration.

Entomologists have known some migratory details of monarch butterflies in North America and a handful of other such insects, many of them pest moths. But speculating about specialized migrants, Chapman says, “there must be thousands of these.”

Orchard orb weaver spider videos


This video from the USA says about itself:

10 December 2016

Large Orchard Orb Weaver Spider with a choice web over a small stream with a nice sound. This is prime real estate and this big Orb weaver is not sharing its space with others. It is fairly common for small Orchard Orb Weavers to share a tangle of webs until they get larger. As is typical this big spider has multiple layers of webs making an effective 3D construction.

Another video of a smaller version of this spider is below here.

This video from the USA says about itself:

Orchard Orb Weaver Spider catching and eating a Carpenter Ant. This Orb Weaver spider is relatively common in Florida and looks like it has red lights glowing on it for defensive purposes, Despite the appearance of two bright red triangles on its abdomen that look like at first glance like an hourglass it is not poisonous like the Black Widow – its “teeth” would have trouble penetrating human skin in any case, but it is very beneficial feasting mostly on mosquitoes and small flies.

These colorful, delicate spiders make circular webs that are usually positioned horizontally or at an angle to the ground, and they typically hang in the middle of their webs. The carapace appears yellow-green, darker on the sides. The abdomen is somewhat elongated and can be variably colored with silver, greens, yellows, reds and some blues. The legs are slender and long.

Male spiders caring for youngsters


This video says about itself:

5 December 2016

Rafael Rios Moura says spider moms handle most of the parental care, but not the Manogea porracea species he studied. Both spider parents take responsibility to protect their egg sac. Linda Rayor of Cornell University said, “To the best of my knowledge, there really aren’t other examples where male spiders step up to care for young or eggs.” Sometimes at the cost of their own lives, male Manogea porracea switch from solitary life to a dad-web upstairs, brushing rainwater off egg sacs. Moura hypothesizes that the females are very delicious to predators considering that many females disappeared by the end of breeding season.

From Science News:

First spider superdads discovered
Males give up solitary life to protect egg sacs, spiderlings — often as single parent

By Susan Milius

9:00am, December 5, 2016

The first normally solitary spider to win Dad of the Year sets up housekeeping in a web above his offspring and often ends up as their sole defender and single parent.

Moms handle most parental care known in spiders, says Rafael Rios Moura at the Federal University of Uberlândia in Brazil. But either or both parents care for egg sacs and spiderlings in the small Manogea porracea species he and colleagues studied in a eucalyptus plantation. The dad builds a dome-shaped web above the mom’s web, and either parent will fight hungry invaders looking for baby-spider lunch. In webs with no parents, only about four spiderlings survived per egg sac. But with dad, mom or both on duty, survival more than doubled, the researchers report in the January 2017 Animal Behaviour.

“To the best of my knowledge, there really aren’t other examples where male spiders step up to care for young or eggs,” says Linda Rayor of Cornell University, who has studied spider maternal care. In a group-living Stegodyphus species, some of the males in a communal web will attack intruders, but Manogea dads do much more. They switch from solitary life to a dad-web upstairs, brush rainwater off egg sacs and share defense, sometimes at the cost of their own lives.

Many male web-building spiders stop feeding as adults because they’re out searching for mates instead of catching food with their web, Moura says. Manogea males, however, stick with a female they mated with and build a new food-catching web. Now Moura would like to know whether such commitment makes males unusually choosy about females, he says.

To predators, females “must be very delicious,” Moura says. In the wild he found that many females disappeared, probably eaten, by the end of the breeding season, leaving dads as the sole protector for 68 percent of the egg sacs.

That high female mortality could have been important for evolution of the dads’ care-taking, says behavioral ecologist Eric Yip of Penn State. Just why this species has such high female mortality puzzles him, though.  Females, geared up for egg-laying, have rich nutrient stores. Yet, he says, “that’s generally true for all spiders — that females are going to be more nutritious and males are going to be mostly legs.”

Spider climbs mushroom, video


This video from the Netherlands shows a spider climbing a toque mycena mushroom.

Roland van Dijk made the video.

Spiders hear better than expected, new research


This video says about itself:

13 October 2016

In a test of hearing airborne noises, a small dark jumping spider stops moving abruptly (red pointer appears) when researchers broadcast a tone similar to the scary droning of the wings of a predatory wasp.

Video: G. Menda, Hoy Lab at Cornell

From Science News:

Be careful what you say around jumping spiders

Arachnids hear airborne sounds over greater distances than thought

By Susan Milius

8:00am, October 15, 2016

Accidental chair squeaks in a lab have tipped off researchers to a new world of eavesdroppers.

Spiders don’t have eardrums, though their exquisitely sensitive leg hairs pick up vibrations humming through solids like web silk and leaves. Biologists thought that any airborne sounds more than a few centimeters away would be inaudible. But the first recordings of auditory nerve cells firing inside a spider brain suggest that the tiny Phidippus audax jumping spider can pick up airborne sounds from at least three meters away, says Ronald Hoy of Cornell University.

During early sessions of brain recordings, Hoy’s colleagues saw bursts of nerve cell, or neuron, activity when a chair moved. Systematic experiments then showed that from several meters away, spiders were able to detect relatively quiet tones at levels comparable to human conversation. In a hearing test based on behavior, the spiders also clearly noticed when researchers broadcast a low droning like the wing sound of an approaching predatory wasp. In an instant, the spiders hunkered down motionless, the researchers report online October 13 in Current Biology.

Jumping spiders have brains about the size of a poppy seed, and Hoy credits the success of probing even tinier spots inside these (anesthetized) brains to Cornell coauthor Gil Menda and his rock-steady hands. “I close my eyes,” Menda says. He listens his way along, one slight nudge of the probe at a time toward the auditory regions, as the probe monitor’s faint popping sounds grow louder.

When Menda first realized the spider brain reacted to a chair squeak, he and Paul Shamble, a study coauthor now at Harvard University, started clapping hands, backing away from the spider and clapping again. The claps didn’t seem earthshaking, but the spider’s brain registered clapping even when they had backed out into the hallway, laughing with surprise.

Clapping or other test sounds in theory might confound the experiment by sending vibrations not just through the air but through equipment holding the spider. So the researchers did their Cornell neuron observations on a table protected from vibrations. They even took the setup for the scary wasp trials on a trip to the lab of coauthor Ronald Miles at State University of New York at Binghamton. There, they could conduct vibration testing in a highly controlled, echo-dampened chamber. Soundwise, Hoy says, “it’s really eerie.”

Neuron tests in the hushed chamber and at Cornell revealed a relatively narrow, low-pitched range of sensitivity for these spiders, Hoy says. That lets the spiders pick up rumbly tones pitched around 70 to 200 hertz; in comparison, he says, people hear best between 500 and 1,000 Hz and can detect tones from 50 Hz to 15 kilohertz.

Spiders may hear low rumbles much as they do web vibes: with specialized leg hairs, Hoy and his colleagues propose. They found that making a hair twitch could cause a sound-responsive neuron to fire.

“There seems to be no physical reason why a hair could not listen,” says Jérôme Casas of the University of Tours in France. When monitoring nerve response from hairs on cricket legs, he’s tracked airplanes flying overhead. Hoy’s team calculates that an 80 Hz tone the spiders responded to would cause air velocities of only 0.13 millimeters a second if broadcast at 65 decibels three meters away. That’s hardly a sigh of a breeze. Yet it’s above the threshold for leg hair response, says Friedrich Barth of the University of Vienna, who studies spider senses.

An evolutionary pressure favoring such sensitivity might have been eons of attacks from wasps, such as those that carry off jumping spiders and immobilize them with venom, Hoy says. A mother wasp then tucks an inert, still-alive spider into each cell of her nest where a wasp egg will eventually hatch to feed on fresh spider flesh. Wasps are major predators of many kinds of spiders, says Ximena Nelson of the University of Canterbury in Christchurch, New Zealand. If detecting their wing drone turns out to have been important in the evolution of hearing, other spiders might do long-distance eavesdropping, too.

Marbled orb-weaver spider couple asleep


This video from the USA says about itself:

26 September 2016

These attractive male and female Marbled Orb Weavers are taking a daytime nap together. The male has attached his “mating thread” across her web and I anticipated much spider action later, but alas other than a few tosses and turns as they slept in their webs when nighttime came they did not mate for at least a few hours and I was denied the chance to see Ms. Orb Weaver partake of Mr Orb Weaver – his last meal. I may lack the patience required for this video task.

How do they reproduce?

There is little information about the mating habits of marbled orb-weavers, although they may behave similarly to other members of their genus (Araneus). Females of these species emit pheromones to attract mates. To court mates, males spin a “mating-thread” across the female’s web. The male moves towards the female across this thread, plucking and vibrating it, and the female approaches him. The male touches the front of the female’s body with his legs, stroking her, until she hangs from the mating thread. Mating takes place in late summer and males mate several times. In some species of orb-weaving spiders, females eat their mates after breeding, this includes European garden spiders, which are closely related and live in the same area. Marbled orb-weavers may also do this; however, males mate multiple times and often survive mating, so cannibalism may not be as common in this species.