There’s a lot of misinformation about spider bites on the internet…and some of it comes from academic websites.

Written by Joe Ballenger

October is an important time for spiders. Spiders sleep through the winter, and right about now is when they’re looking for places to hunker down. Consequently, we get a lot of pictures of spiders in people’s houses.

A few days ago, on the Ask an Entomologist Twitter feed, I got someone sending us a tweet of a Yellow Sac Spider. It’s a common species which invades houses at this time of year, so I kind of expect to see pictures of them occasionally.

This is a Yellow Sac Spider, Cheiracanthium sp. of some sort. Their bites are typically like a bee sting, although there is a wide variety of symptoms. Some people report severe pain which lasts for a couple of hours, there may be a rash, and some people get nauseous. It’s not fun, but it’ll be over in about a day or so…without lasting damage.


Yellow Sac Spider on a finger. Image credit: Andrew Hoffman. License info: CC-BY-NC-ND-2.0

It should be pointed out that these descriptions come from people who were bothered enough to seek medical attention. Given how often these spiders are found in people’s homes, it’s very likely that these symptoms all reflect a worst-case scenario. Compared to a Black Widow, this is pretty mild.

The problem is that a lot of sources say that this spider has a bite similar to the Brown Recluse in that it causes a big wound that festers for weeks. This sort of bite is called a necrotic bite, and that means it makes a lot of dead flesh.

This rumor has made it onto quite a few University Entomology extension websites. Some notable examples include the University of Nebraska, Utah State University, Washington State, and the University of Minnesota. Often times, University extension websites link to one another…like the University of Wyoming website which links to the Utah State University website.

There are some fact sheets, however, which do get it right. The Penn State University website is one of these.

This rumor was addressed in the scientific literature in 2006, by Rick Vetter. Rick Vetter is a bit of a celebrity among entomologists, because he’s made a career of pointing out that spider bites are rarely correctly diagnosed by medical professionals. He’s a professional spider-mythbuster.

In order to investigate whether the bites of Sac Spiders caused necrosis, he formed a group of scientists and they personally investigated as many spider bites as they could. They’d take a call from a poison control center, get the person to collect the spider, and then follow the person’s symptoms as they recovered. He also went through the literature, and looked only at cases where the spider had been collected and positively ID’d.

Of the 40 Sac spider bites where the spider had been collected, only one bite from Europe produced a necrotic wound. The wound was about a quarter-inch across, and nothing like the wounds produced by Brown Recuses. Vetter accepts the wound was from the spider’s venom, although I kind of wonder if it’s an infection.

Regardless, Vetter was eventually able to trace the origins of the myth back to tests run on Guinea pigs. Guinea pigs are known to be more sensitive to spider venom than people are. In this case, the tests run on Guinea pigs weren’t as informative as they should have been. The researchers had been unwittingly working with a model poorly suited to this sort of study.

Doctors who were looking to diagnose patients saw these papers, and noticed some of their patients had wounds which looked similar. Wanting a quick answer, they diagnosed the wound as a ‘spider bite’ and sent the patients on their way. Other doctors saw these case reports, made similar diagnosis, and the whole thing snowballed from there.

In science it’s difficult to prove a negative, but it’s pretty clear that Sac spiders don’t have the same venom as the Brown Recluse. From Vetter’s research, it’s not possible to definitively say that these bites can’t cause necrosis in rare and sensitive individuals…but it’s also clear that comparing their bites to those of a Brown Recluse is not an accurate description of the bite.

Unfortunately, the rumor continues today and has made into University Entomology Extension websites. Typically, they’re good sources of information for bug-related stuff…but even entomologists aren’t perfect.

Works Cited

Vetter, R. S., Isbister, G. K., Bush, S. P., & Boutin, L. J. (2006). Verified bites by yellow sac spiders (genus Cheiracanthium) in the United States and Australia: where is the necrosis?. The American journal of tropical medicine and hygiene, 74(6), 1043-1048.


Posted in News, Research, Uncategorized | Tagged , , | Leave a comment

Never growing up: why are there insects which *don’t* go through metamorphosis?

Written by Joe Ballenger

If someone begins a statement with ‘this might be a dumb question, but…’ my ears usually perk up, because it’s very likely that something interesting is about to follow.

This is a great question, because she’s asking about lifestyles which aren’t really commonly known outside the entomology community.


Male Acanthopsyche moth. A female is pictured below the fold. Image credit: Janet Graham, via Flickr. License info: CC-BY-2.0

In the laboratory, we can suppress the process of metamorphosis by treating insects with growth regulators. Many of these growth regulators are also used as pesticides, specifically for mosquitoes.

Although it pays for humans to be able to control this process, there are some benefits to abandoning metamorphosis altogether. In fact there are many moths, beetles, flies, and an obscure group of parasitic insects called Strepsipterans, which have abandoned this process. Some of these insects just look like larvae as adults, but others have completely done away with the process altogether.

So what do these lifestyles look like, why do they develop this way, and how does this system work?

Continue reading

Posted in Developmental Biology, Physiology, Taxonomy | Tagged , , , , , , , , , , , , | Leave a comment

How much water can ants drink?

Written by Joe Ballenger

Your Name: charles
Your Bug Question: How much can an ant drink of water?

I thought this question about how ants drink was really cool. It’s a question that has a pretty simple answer at first, but it also gets a lot more complicated when you delve into the details of how insects uptake fluid.

Ants, which are social wasps in the family Formicidae, are an insanely diverse family of insects. There’s over 12,000 species of ants currently described, and there could be as many as 20,000. To give you an idea of how this compares to mammals, there’s only about 40 species of dog living today.

So there’s a lot of ants, which have many different lifestyles. However, there’s only so many ways to collect fluid…and different tactics mean that they each drink a certain amount.

First, though, we need to explore how insect mouths work because drinking is a really complicated process for insects.

How do insects drink?

Like people, insects use their mouths to drink. They can do so in some pretty different ways, but they use the same piece of equipment to do this.

What parts do insects use to drink?


A dissection of grasshopper mouthparts, via Wikimedia Commons. Modified by Joe Ballenger. Author info: Heds. License info: Public Domain

When we talk how insects drink, we’re talking about how they use one very specific part of their mouths. Insects have a lot of different moving parts in their mouths, and each part has some fairly specific functions. To make matters more complicated, most groups have evolved some very significant modifications of this design.


The mouthparts of ants in particular, are relatively unmodified and are pretty close to the mouthparts of the grasshopper to the left. Their mouths contain a labrum, which is used to hold food in the mouth while it’s being processed. Ants use the mandibles to grasp food, and the maxillae to process solid food. The labium is used to hold food in the bottom of the mouth while it’s eating.


Ant labium, modified from image above by Joe Ballenger

The ant uses the labium for drinking, and it’s basically the ant equivalent of the human tongue. The labium is subdivided into several other parts. The hypopharynx is used to hold the liquid, while the glossa transports the liquid.


It should be noted that the grasshopper labium is a little different than the ant labium, but I couldn’t find any great pictures of the ant labium which showed the modification.

How do ants drink?

Like mammals, ants can drink using two different methods…licking and sucking.


Licking is accomplished much like a dog lapping up water. The glossa is used to transport water into the hypopharynx in a physical manner. Yellowjackets use this method to drink water:


Sucking is accomplished in a way similar to how humans do it. Negative pressure is used to draw liquid into the hypopharynx, where it’s passed into the digestive system.


So how much can ants drink?


Camponotus rufipes carrying droplet of water. These ants also suck from the water drop, and can also carry droplets of water back to the nest. Image credit: Paul & Roces 2003

How much an ant drinks depends on the size of the ant’s head, and how it drinks. Ants can have workers of different sizes, and bigger workers will drink more. Different ant species can be different sizes, and different individuals take different amounts of time to drink and will intake varying amounts of fluid.

So this answer is a bit complicated.

The best answer comes from the mid-sized ant Camponotus mus. In a single sitting, these ants can drink about 6-8 microliters of sugar water. Larger ants will drink slightly more, and smaller ants will drink slightly less.

Paul & Roces 2003 measured fluid intake in a bunch of different ant species, but they didn’t look at volume. They only calculated rates, and only gave a range of times the ants drank. However, this data still allows us to get a pretty good range for how much ants drink.

Based on this information, it seems the largest amount that an ant could drink is about 35 microliters. The smallest amount they generally choose to drink is .1 microliter. The typical ant probably drinks about 6-8 microliters of water in a single sitting.

What’s a microliter?

One of the major issues with the scientific literature is that it’s written by scientists, for scientists. Consequently, papers tend to use units which don’t mean a whole lot to most folks. To understand how much volume we’re talking about above, you need to know what a microliter is.

How much water a microliter contains is very difficult to imagine, because this is a vanishingly small volume. A one-liter pop bottle contains exactly one million (1,000,000) microliters of soda. One way to put this is that it would take about 200,000 ants to drain a one liter bottle of soda if we’re using data for Camponotus mus.


One drop of water is roughly 30 microliters. It’s an imprecise measurement, to be fair, but it works well for a visual gauge of liquid volume. Picture credit: Joe Ballenger

I think there’s a more accessible unit we can use to compare, though. We can compare these numbers to a drop of water.

While in graduate school, I needed to be able to quickly measure small amounts of buffer. To do this, I measured how much water was in a single drop exuded from a plastic eyedropper. Water drops off the pipetter at about 33 microliters of water, so one drop of water is about 33 microliters.

Given this information, the largest ants can drink about one drop of water in a single sitting. The smallest ants probably choose to drink about 1/1000th of a drop. A mid-sized ant, in a typical drinking session, probably chooses to drink 1/5th of a drop of water in a single setting.

The Bottom Line

Ants are small, but they can drink a lot of water depending on their body weight. Your typical ant, in an average setting, probably drinks about 7 microliters of water. This is equivalent to 1/5th of a drop of water.

It should be noted that this might not necessarily reflect how much water an ant can bring back to the nest. Many ants, particularly those which can’t store water in their stomach, actually carry droplets of water back to the nest. These drops can be significantly larger than what’s discussed here

On the plus side, if you’re worried about ants stealing your entire bottle soda…there’s no reason to worry because you’ve got enough to share with your six-legged friends.

Unless, of course, there’s a quarter million ants heading your way. Then you’ve got some major problems.

Works Cited

  1. Josens, R. B., Farina, W. M., & Roces, F. (1998). Nectar feeding by the ant Camponotus mus: intake rate and crop filling as a function of sucrose concentration. Journal of Insect Physiology, 44(7), 579-585.
  2. Paul, J., & Roces, F. (2003). Fluid intake rates in ants correlate with their feeding habits. Journal of Insect Physiology, 49(4), 347-357.

Thanks to Biker Lee and Sébastien de Valeriola for helping us acquire some of the literature used for this post.

Posted in Behavior, Ecology, Physiology, Uncategorized | Tagged , , | Leave a comment

Bees carrying leaves? What’s up with that?

Written by Joe Ballenger

Your Name: Clark

Your Bug Question: I noticed a small flying insect about the size of a honey bee, fuzzy, all black flying around with a small leaf in its legs. It flew down between some small rocks next to a cement pad and dissapeared. It flew out a minute later without the leaf and returned with another leaf or section of a leaf. I watched it repeat this several times. Any idea what this insect is and what it is doing?

As Nancy wrote, IDing insects can be very hard because you often need to see tiny features of the insect most people wouldn’t think to photograph.

Thankfully, not all bugs are this way. Some insects have behaviors that are pretty unique, and can be used to ID them with a surprising degree of certainty. The behavior that Clark is describing is one such example. It doesn’t happen too often…but we love it when it does.

Leafcutting bees, family Megachilidae, are pretty unique among bees because they snip off pieces of leaves to line their nests. Like other bees, they also feed on pollen and nectar. The larvae eat the pollen, and the leaves are used to give them a comfy little house to live in. Some like to build nests in cracks and crevices, others like to build their nests in hollow plant stems, and others take over old nests left by carpenter bees. One species even uses old snail shells to build its nests.

Not all of these bees are pollinators, however. Several species are parasitic, and take over nests from closely related species. The Cuckoo-bees, Coelioxys sp., are probably the best known example.

My favorite Entomo-YouTuber, Nature1UpClose, has an excellent video which describes the lifecycle of this bee. They’re very important pollinators, especially in agricultural situations. They do cause some damage to the plant by removing leaves. Because they pollinate the plants, they’re usually more of a benefit to the system than they are a pest.

Megachilids are pretty cool…and they’re one of the bees that’s not talked about too frequently when talking about pollinators.

Posted in Behavior, Ecology, Pollination, Uncategorized | Tagged , , , , , , , | Leave a comment

What is it like to be a scientist?

Written by Joe Ballenger

Your Name: Chelsea
Your Bug Question: Hi, I’m a middle school student and I was hoping you could answer a few of my questions about being an entomologist for a research paper I’m writing.

Your Name: Jensen
To Whom it may concern,
I am a (high school) student and I have a project where I interview someone about their job. I have decided to interview a zoologist and I was hoping that you could answer a few questions.

Awhile back, Nancy wrote an article explaining what an entomologist does in What Is an Entomologist? She also recently talked about what she’s doing in Ecuador and her background in a few live posts. She’s doing some amazing things, and they’re worth watching because she answers these questions from her perspective.

Her posts are a great introduction to the topic of entomology, because she explains what scientists are and why we study bugs. However people still ask us some more in-depth questions that I wanted to address here, because they shed some light on what doing science is like.

Science is a job like any other, and no two of us have the same job description. In general, though, we have a time we need to be at work. There are meetings, bosses, and things that everyone else has. You have projects you have to get done, work you need to prioritize, and the like. Everyone with an office job does all of these things, so we can identify with a lot of other professions.

Sure, we’ve talked about research. We do that all the time, and it’s an important part of talking about science. Specifically, we’ve talked about the results of research…but not doing the research itself.

So…what is it like to be a scientist?

Continue reading

Posted in Culture, Education, Uncategorized | Tagged , | 2 Comments

Do insects feel pain?

The last two questions we tackled revolved around the cognitive abilities (communication, and personality) of arthropods, specifically insects and spiders. These are really tough questions to tackle because a lot of people, even (especially?) those who genuinely like insects and spiders, want to humanize them as a way to identify with them.

I think it’s a good thing to want to identify with these animals, so long as we’re making proper comparisons. Sometimes, however, this very human impulse can get us into trouble…like this Twitter post by the Featured Creature twitter account.

This image is typically shared as an example of maternal care in jumping spiders. Although maternal care does exist in this group, it doesn’t typically involve the mother carrying them to a new location in the manner shown.

Assuming the picture is real (see Chris M. Buddle’s comment), the activity pictured here is most likely cannibalism. Instead of being an endearing picture, this is more of an example of how our desire to identify with insects and spiders can cloud our image of how they behave. This desire has a name, it’s called ‘anthropomorphism’…which means to imbue human characteristics or motivation onto non-human organisms.

I wanted to open our discussion of insect pain up with that story, because it’s a very important point to make. Insects react to the world differently than we do, and when it comes to cognition it’s very difficult to separate our motivations from theirs.

Continue reading

Posted in Behavior, Physiology, Uncategorized | Tagged , , , , , , , | 3 Comments

So You’re In the Tropics, Named a New Species Yet?

Written by Nancy Miorelli

The short answer is “No.”
The long answer is “No.” but with with a bit more explanation. The first is that I’m a communicator, an ecologist, and don’t have a lot of the proper equipment.

Have I seen a new species to science? I have absolutely no doubt. Did I know it was a new species when I saw it? No, probably not. There’s just so much diversity here it hasn’t even been quantified.

Our moth sheet in Ecuador. So yeah there's probably a dozen or so new species on it. Anyone want to look at really tiny brown moths?

Our moth sheet in Ecuador. So yeah there’s probably a dozen or so new species on it. Anyone want to look at really tiny brown moths?

For example. There’s about ~20,000 species of butterflies in the world. Ecuador has close to 4,000 butterfly species. Maqui, the reserve that I’m in, has close to 200 butterfly species. So our one little 6,000 hectare (15,000 acre) reserve has 0.5% of the butterfly species of Ecuador!  And that’s just butterflies – a big charismatic group that has a lot of identification work in it. Beetles, moths, and little wasps on the other hand are a whole nother animal(s). There’s a lot more of them, an there’s a lot more little ones, and a lot more that live in tropical areas that are hard to get to.

Continue reading

Posted in Taxonomy | Tagged , , , , , , , , | 2 Comments