IB 109
Insects and People
Parasites
Public service films
1. What species of mosquitoes are the focus of these films?
-“Private Snafu vs. Malaria Mike”
-“It Must be the Neighbors”
2. Why are these mosquitoes medically important?
3. Which studios or agencies produced these films? Who is the target audience?
4. What preventative measures are recommended?
5. Which film do you feel is the most effective at conveying its message? Why?
Parasites
Inspect the specimens of human parasites provided. Which are the ectoparasites and
which are the endoparasites?
Order
Phthirus pubis
Pediculus humanus capitus
Pediculus humanus humanus
Ctenocephalides felis
Amblyomma americanum
Ixodes scapularis
Dermacentor variabilis
Describe morphological traits shared by the ectoparasites you see.
Ecto/Endo
Do endoparasites share any morphological characteristics?
What diseases, if any, are vectored by these arthropods?
Pathogens
For the following pathogens, provide the information requested:
Pathogen
Type of microbe
Arthropod vector
Disease
Babesia bigemina
Borrelia burgdorferi
Plasmodium falciparum
Trypanosoma brucei
Trypanosoma gambiense
Yersinia pertis
Morphology
1. Mouthparts: compare the slides demonstrating mouthparts of mosquitoes and stable
flies. Which do you think is a pool feeder and which a vessel feeder? Explain your
answer.
2. Examine the mosquitoes on display. What anatomical traits do you think would be
most useful for identifying disease-carrying larval and adult mosquitoes in the field?
Anopheles
Culex
Aedes
Mites
1. Follicle mites (Demodex follicularum) are frequent residents of human hair follicles,
where they feed on sebaceous gland secretions. It has been estimated that approximately
75% of the human population harbors these mites, which generally cause no harm (other
than psychological, perhaps, once their presence has been pointed out). In this exercise,
you will be asked to pluck out several eyebrow hairs; take the most promising one and
place it on a microscope slide, cover with a small droplet of oil and a cover slip, and look
for the presence of a mite at the base of the hair.
2. Dermatophagoides pteronyssinus, the house dust mite, is not a parasite of humans in
the sense that it does not reside on or feed from the human body. But it does consume
human body parts – specifically shed skin flakes that accumulate in house dust. Earlier
today, samples of house dust were placed in an 80% ethanol solution. These will have
been soaking for approximately four hours. When you get to lab, add to the ethanol
solution some saturated sodium chloride solution. Ethanol is absorbed by the mites and
reduces their density; the saturated salt (as opposed to water) increases the density
difference between the mite bodies and the solution. Thus, the bodies of the mites will
rise immediately to the surface of the solution, where they can be sampled and examined
under the microscope. Non-mite debris should remain at the bottom of the beaker.
Reference: A. Fain and B. J. Hart 1986. A new, simple technique for extraction of mites,
using the difference in density between ethanol and saturated NaCL (preliminary [sic]
note). Acarologia 28: 255-256.
Which dust samples contain the highest densities of mites?