Who is Stronger?
VS
The Bess Bug
Odontotaenius disjunctus
Aliases
•Betsy Beetle
•Patent-leather
Beetle
•Passalid Beetle
Order Coleoptera
• Largest order of organisms,
including over 350,000
species.
• One out of every four
animals in this world is a
beetle.
• They all have hard, shelllike forewings.
– A tough protector of the
beetle's delicate hind wings
and soft abdomen.
– Protects beetles as they
squeeze through narrow
passageways and burrow
into decaying wood or sandy
soil.
Where Does it Live?
• Commonly found in decaying logs from Texas to
Florida and as far north as Canada.
• There are only two species in the U.S., while over
500 species can be found in the tropics.
Physical Characteristics
• Large, shiny, black
beetle
• 3 body parts - head,
thorax, abdomen
– The thorax of this beetle
has two sections,
allowing its hard body
to move more freely.
• 3 pairs of legs
– gold-colored fringe
• A pair of feathery
antennae
• Small horn and long
jaws protrude from the
front of the head
Diet
• They prefer hardwood—oak,
elm, and other deciduous
trees—that is well decayed
and falls apart easily.
• Wood is an indirect food
source.
– Beetles don't have symbiotic
bacteria in their gut that help
them digest the cellulose in
decaying wood. Bess beetles
process wood in their digestive
system, and then a fungus
grows on the beetles' feces. It is
this fungus that give beetles
nourishment.
• Larvae eat a well-chewed
mixture of beetle feces and
wood.
Other Fun Facts
• They are social insects and raise young in adult
pairs.
• Adults stridulate by rubbing wings.
• Larvae stridulate by rubbing legs.
• Males have a prominent horn on their head.
• They have 2 pairs of wings but rarely fly.
Lab Purpose
• Observe and calculate the pulling power of a Bess
Bug.
• Determine the relative pulling strength of a Bess
Bug compared to a human.
• Discuss how strength is an adaptive advantage for
insects.
Strength?
* Brute Strength - How much can you lift/pull/push?
* Relative Strength - How much can you lift/pull/push in
comparison to your own body mass/weight?
• size (relative to their
own body mass)
• muscle arrangement
• muscle attachment
• body structure
• flexibility
Procedure Highlights
• If the bugs are scared or feel threatened, they may not
move.
• The harness should be placed between the thorax and
abdomen. It should go down their back!
• The beetle should start on the cloth.
• The Petri dish should start on the table.
Procedure Highlights
• Any time the bug moves the dish, add a washer.
• Move the bug and Petri dish back to its starting position if it
gets off track. Do not pull or drag the bug. Pick it up!
• Handle the beetle gently and with respect!! Grasp it at the
sides.
• Carefully remove the harness and return it to the container
at the conclusion of the lab.
Measurements
• Mass of a washer
• Mass of the Petri dish
• Mass of the Petri dish
with beetle
• Mass of the beetle
• Length, width, and
height of the beetle
Calculations
• Total pulled washer
weight
• Beetle pulling power