Unit 11 in Entomology
Unit 11: Insect Parasitism
In this unit, we’ll differentiate between the three types of symbiosis, describe the different ways to classify
parasites, discuss the costs and benefits of endo versus ecto parasitism, differentiate between parasite
and parasitoid, define hyper, multiple and gregarious parasitoids, and explain in insect terms why being
small is actually good.
We’ll discuss more about parasites, but for the time being, take a look at the
Both of these are lice that can be found on chickens.
One is found on the body
and one is found on the feathers.
Take a look at the morphological differences.
Why do you think
they’re shaped so differently?
These are some things to think about as we discuss insect parasitism.
In this unit, we’ll discuss insects that parasitize humans, mammals, and other arthropods.
You will first
learn the difference in three symbiotic relationships, and between parasite/parasitoid, parasitoid/predator,
and about various endo and ecto parasites.
Prepare yourself for some repugnant pictures that illustrate
some damage that insect parasites can do to other animals.
Symbiotic relationships refer to interactions between two different species.
In fact, when broken into its
Greek roots, the word symbiotic means “life together”.
Sym means together and bio means life.
unit you’ll first learn about three different types of symbiotic relationships: mutualism, commensalism, and
The balance of the unit will then focus on various aspects of parasitism.
These terms are
generally used to describe the relationship between species, but can also be used for interactions within a
species, particularly humans.
Mutualistic relationships are those in which both species involved benefit.
For example, most friendships are a mutualistic relationship.
As you can see in this picture, ants and
aphids have a special mutualistic relationship.
The aphids feed the ants by secreting a sugary solution
called honeydew through cornicles on the tip of their abdomen.
These ants, in return, protect the aphid
by attacking predators such as ladybugs.
The second type of relationship is commensalism.
In commensal relationships, one species benefits but
the other neither profits nor is harmed.
In this picture, orchids are growing on the side of a tree.
orchid needs the tree for support and protection, but the tree doesn’t benefit, not is it harmed, by the
Relationships in which one species benefits at the expense of the other is a parasitic
A good example of this is a mosquito and a human relationship.
As pictured here, this
mosquito has inserted her mouth part into a human to draw out a blood meal.
The human will have a
nice itchy lump where the mosquito has injected its poison, but the mosquito will use the protein it got
from the blood to make her eggs.