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Sow Bug and Pill Bug Experiment

Animal Behavior

Dr. Jackson

22 March 2023

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Abstract

In this lab report, constructed of a series of 5 individual experiments, my groupmates and I

analyzed the behaviors of two species of terrestrial isopods: pill bug (Armadillidium vulgare) and

the sow bug (Porcellio laevis) when each were placed in various environmental conditions.

These conditions ranged from wet/dry, rough/smooth, dark/light, and warm/cold; essentially,

observing which side was preferred from each species. Prior to beginning the experiment, we

knew little to nothing about these two species, so comprehensive assessment alike the series of

tests that was conducted would help strengthen any grey areas.With that being said, I

hypothesized that the sow bug (Porcellio laevis), because of its larger shape, would prefer

rougher surfaces, dryer climates, and cold and darker grounds because of its dark appearance in

color. For the pill bug (Armadillidium vulgare), I hypothesized that because it showed a tendency

to curl into a ball and exclude itself from external factors and its smaller appearance that it would

prefer drier climates, smooth surfaces, warmer temperatures, and lighter grounds. Based off my

hypothesis, I ultimately believe that there is a huge difference between the pill bug and sow bug.

Introduction

To begin, the basis of our experiment is focused on isopods. For context, an isopod is an

order of crustacean that can inhabit anywhere on land to as far out as the sea. Our two isopods in

question were the sow bug and pill bug. Starting with the sow bug, according to an article titled

Studying Behavior in Invertebrates (Sow Bugs), they fall under a category known as arthropods,

which are not insects, however, they are closely related to them. The sow bug has an oval shape

with

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fourteen separate legs, organized into seven pairs of two. From the superior view of the creature,

rests a

pair of antennae, which aid in the sow bugs ability to touch, hear, smell, and in some rare cases

taste. Furthermore, the article states the sow bug is broken up into three parts: its thorax, head,

and abdomen. The head acts as the sensory organ to aid in the five senses. The thorax acts as the

anchor for the legs which act as a movement organ, and the abdomen is where majority of the

digestion, excretion, and reproduction takes place. The color of the sowbugs used in this

experiment were dark brown and black in some areas, which is a key ting to note when the color

of their environment they were placed in was in question. In comparison to its counterpart, from

first glance, the sow bugs were more active than its counterparts. This is another key thing to

note since, our overall study was centered around the movement towards the arthropod’s

preference. On the other hand, the pill bug, which is commonly known as a rollie pollie, is an

isopod that has accustomed itself into primarily living on land. The pill bug’s physical

appearance is like that of the sow bug, except it is significantly smaller. In addition, when it

touched with a degree of aggression it is not used to, it will roll into a ball, hence why it is

sometimes referred to as a rollie pollie. At the beginning of the experiment, I predicted that the

structure of these bugs, will be a key determining factor for the bugs’ decision. For behavioral

preferences regarding habitats, according to a scholarly article written by Shuang Wang titled,

Body Size and Weight of Pill Bugs (Armadillidium vulgare) Vary between Urban Green Space

Habitats, it states that pill bug populations thrive in moist climates and damp soils; a key thing to

note once I begin reviewing the results from our findings. Bridging into the behavior of these

bugs, an article titled Sowbugs and Pillbugs, by Michael F Potter from the University of

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Kentucky, states that “sowbugs and pills bugs may leave their natural habitats at night, and crawl

about over sidewalks and that they mostly require moisture.” This is a key thing to note being

that the color of the ground and the moisture of the environment was tested.

Method

The method section of this experiment was a simple being that majority of the work was based

on the behavior of the bugs and not of the experimenters. First. My group decided to start with

testing the behavior of the sow bugs, but for no reason. We grabbed a plastic container provided

by our instructor and transferred eight sow bugs into the container. The first test for the sow bugs

was to determine whether it preferred a wet or dry surface. In order to imitate a wet surface, we

took a wet piece of cloth and sprayed water on it until it was dripping wet and set it on one end

of the table, while the other half was left untouched. A timer on an iPhone 11 Max Pro was set

for two minutes and thirty seconds, with thirty second intervals in between to record the number

of sow bugs that were on each side. However, for each thirty second interval, a different ratio of

sow bugs was to be set so that we could get a better observation of their preference. For example,

at the first thirty second interval, four sow bugs were present on the wet side while four were

present on the dry side. For the second thirty second interval five bugs were place on the wet side

and three were placed on the dry side. For the third thirty second interval six were placed on the

wet side and two were placed on the dry side. For the fourth thirty second interval, three were

placed on the wet side, leaving five on the dry side. On the fifth interval, two were placed on the

wet side, and six were placed on the dry side. For the second part of our experiment, we assessed

whether sow bugs preferred a rough or smooth surface. To mimic a dry surface, we used a rough

sandpaper to resemble roughness in the wild and left the smooth side untouched, like that of the

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dry side in the first experiment. Like the first part, each test was constructed so that a different

ratio of sow bugs was on each side at a given interval. At the first thirty second interval, four sow

bugs were present on the rough side while four were present on the smooth side. For the second

thirty second interval five bugs were place on the rough side and three were placed on the

smooth side. For the third thirty second interval six were placed on the rough side and two were

placed on the smooth side. For the fourth thirty second interval, three were placed on the rough

side, leaving five on the smooth side. On the fifth interval, two were placed on the rough side,

and six were placed on the smooth side. Observations were recorded. For the third half of the

experiment involving sow bugs, we analyzed whether they preferred standing on a darker surface

or a lighter surface. To mimic darker and lighter surfaces, we took two pieces of paper; one being

black and the other being white and set them on opposing ends. The intervals were as such: for

the first thirty second interval, four sow bugs were present on the dark side while four were

present on the light side. For the second thirty second interval five bugs were place on the dark

side and three were placed on the light side. For the third thirty second interval six were placed

on the dark side and two were placed on the light side. For the fourth thirty second interval, three

were placed on the dark side, leaving five on the light side. On the fifth interval, two were placed

on the dark side, and six were placed on the light side. The last for the sow bugs were to test

whether they preferred warm or cold surfaces. To mimic a warm surface, we took a warming pad

and set it underneath one side and took a relatively cold ice pack and set underneath the opposing

side. The thirty second intervals were as follows: at the first thirty second interval, four sow bugs

were present on the warm side while four were present on the cold side. For the second thirty

second interval five bugs were placed on the warm side and three were placed on the cold side.

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For the third thirty second interval six were placed on the warm side and two were placed on the

cold side. For the fourth thirty second interval, three were placed on the warm side, leaving five

on the cold side. On the fifth interval, two were placed on the warm side, and six were placed on

the cold side. This now concluded our test for the sow bugs. Using this test, graphs were

constructed, and chi square analyses were calculated to determine whether our results we

observed were by chance or actual findings worth recording. Our next focus was the pill bugs.

Now for the pill bugs, we had a much more difficult time handling them, being that whenever

they were touched a certain way, they would immediately curl up into a ball, therefore, making

us wait a minute or two before they would be ready to walk around and move. Also, to note, they

were not as active as the sow bug. For the first experiment with the pill bugs, we tested whether

the pill bugs preferred a wet surface or a dry surface. A cloth was dampened, and placed on the

other side, and the opposing was left alone to resemble a dry side. The time intervals for the pill

bugs were like the sow bugs, however, it is still worth noting so that the results can be better

tracked. At the first thirty second interval, four pill bugs were present on the wet side while four

were present on the dry side. For the second thirty second interval five bugs were place on the

wet side and three were placed on the dry side. For the third thirty second interval six were

placed on the wet side and two were placed on the dry side. For the fourth thirty second interval,

three were placed on the wet side, leaving five on the dry side. On the fifth interval, two were

placed on the wet side, and six were placed on the dry side. The second test for the pill bugs were

to test whether they preferred a rough or smooth surface. The same configuration that was

assembled for the sow bug was set for the pill bug and two minute and thirty-minute timer was

set. The time intervals were as follows: at the first thirty second interval, four pill bugs were

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present on the rough side while four were present on the smooth side. For the second thirty

second interval five bugs were place on the rough side and three were placed on the smooth side.

For the third thirty second interval six were placed on the rough side and two were placed on the

dry side. For the fourth thirty second interval, three were placed on the smooth side, leaving five

on the dry side. On the fifth interval, two were placed on the rough side, and six were placed on

the smooth side. The third assessment for the pill bugs was to determine whether they preferred

standing on a dark surface or a light surface. A piece of paper was taken; with one side being

black, while the other side was white and placed underneath the container. The timer was set for

two minutes and thirty seconds with thirty second intervals to assess the movement and to

replace the bugs. The interval placements for dark vs light were as follows: at the first thirty

second interval, four pill bugs were placed on the dark side while four were placed on the light

side. For the second thirty second interval five bugs were place on the dark side and three were

placed on the light side. For the third thirty second interval six were placed on the dark side and

two were placed on the light side. For the fourth thirty second interval, three were placed on the

dark side, leaving five on the light side. On the fifth interval, two were placed on the dark side,

and six were placed on the light side. The last test for the pill bugs were to assess whether they

preferred a warm or cold surface. To simulate a warm surface, we placed a heating pad

underneath one side and a cold pack on the other: like the configuration for the sow bug assay. A

two minute and thirty-minute timer were set with thirty second intervals in between. The interval

placements were as follows: at the first thirty second interval, four pill bugs were present on the

warm side while four were present on the cold side. For the second thirty second interval five

bugs were place on the warm side and three were placed on the cold side. For the third thirty

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second interval six were placed on the warm side and two were placed on the cold side. For the

fourth thirty second interval, three were placed on the warm side, leaving five on the cold side.

On the fifth interval, two were placed on the warm side, and six were placed on the cold side.

Observations of movement were recorded. After all the numbers were recorded into a table, the

numbers were then implemented into line graphs for each of the conditions for each species.

Results/Discussion

The bar and line graphs for each species under each set of conditions are shown below.

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The line and bar graph essentially show the same thing; however, bar graphs can easily read.

Starting with the wet vs. dry test it can be inferred that both the sow bug and the pill bug

preferred wet over dry, however the pill bug significantly preferred wet over dry whereas the wet

vs dry for the sow bug was almost the same. For the rough vs smooth tests, both the pill bug and

the sow bug preferred rough surfaces over the smooth surfaces. This can be best explained by an

article titled Sowbugs and Pillbugs written by Barb Ogg, stating that are usually “found in moist

soil or rotting wood.” The texture of soil and rotting wood is rough, therefore, during the

experiment, the bugs may have speculated that this rough surface was the soil that they are

accustomed to in the wild. The next test was dark vs light. To my surprise, as a contradiction to

the articles that were in the introduction, the pill bug significantly preferred dark surfaces over

light surfaces, while the sow bug preferred light surfaces over the darker surfaces. In an article

by Michelle Ramsey titled Holy Moly It’s a “Roly Poly-Sowbugs and Pillbugs,” “they spend

daylight hours in moist, dark habitats.” This contradicts my findings being that the lights were on

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in the classroom, essentially indicating to the sowbugs that it is in the daytime; therefore, I am

uncertain as to why they preferred the lighter climates based off the article’s findings. That is

something to take now, if this experiment was repeated. The last experiment was the warm vs

cold assay. To my surprise, and contradicting to my findings in the articles, was that the sow bug

significantly preferred the cold surface, while the pill bug slightly preferred the warmer surface

over the cold. According to scientist, if both species before most and dark climates, one can infer

that that the temperature of this climate would be warm rather than cold. However, it is worth

mentioning that they are only active during the nighttime, thus further defending the argument

that they are active on colder surfaces, rather than warm.

Conclusion

All in all, based off the bar graphs and line graphs presented for only two out of the four

scenarios, the pill bugs preferences were the same whereas the remaining two scenarios their

preferences differed in significantly. The two scenarios where they were the preferred the same

setting were wet vs dry, where both pill and sow bugs preferred wet over dry and the scenario of

rough vs smooth where both pill and sow bug preferred a rougher surface over a smooth surface.

The two scenarios where they differed were when dark vs light was tested and warm vs cold,

where the pill bug preferred dark and warm, while the sow bug preferred light and cold. Based

off these findings, my ultimate hypothesis that these two bugs were significantly different than

one another. One can infer that these two bugs are different, however it is difficult to exaggerate

their differences, being that they showed similarity in two of the scenarios tested. If this

experiment were to be continued, great emphasis would be placed on the two scenarios where

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they were the same, in order to conclude that there is a significant difference between the two,

since after all, they are both derived from different genus and species, given their scientific

names.

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Works Cited

Holy moly it's a "roly poly" - sowbugs and pillbugs. ANR Blogs. (n.d.). Retrieved March 22,

2023, from

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=12567#:~:text=Sowbugs%20and

%20pillbugs%20are%20most,sidewalk%20areas%20during%20the%20day.

Sowbugs and pillbugs. Entomology. (n.d.). Retrieved March 22, 2023, from

https://entomology.ca.uky.edu/ef439#:~:text=Sowbugs%20and%20pillbugs%20may%20le

ave,of%20houses%20at%20ground%20level.

Sowbugs Lancaster County and pillbugs - university of nebraska–Lincoln. (n.d.). Retrieved

March 23, 2023, from https://lancaster.unl.edu/pest/resources/001Sowbugs.pdf

Studying behavior in invertebrates (sow bugs): Free paper examples. Premium. (n.d.). Retrieved

March 22, 2023, from

https://premium-papers.com/studying-behavior-in-invertebrates-sow-bugs/

Wang, S., Zhu, Z., Yang, L., Li, H., & Ge, B. (2023, February 26). Body size and weight of pill

bugs (armadillidium vulgare) vary between urban green space habitats. MDPI. Retrieved

March 22, 2023, from https://www.mdpi.com/2076-2615/13/5/857

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