A short present about host seeking behavior of mosquitoes and sand flies. It can cover the mechanisms and factors involved in host seeking behavior.

1. HOST SEEKING BEHAVIOR OF MOSQUITOES
AND SANDFLIES
BY
KUMARESAN.S
M.SC., [PHE]
ICMR – VCRC
PUDUCHERRY.

2. CONTENTS:
• DEFINITION FOR BEHAVIOUR
• CLASSIFICATION OF BEHAVIOUR
• VARIOUS TYPE OF BEHAVIOURS EXIST IN MOSQUITOES
AND SANDFLIES
• PURPOSE OF STUDYING THE BEHAVIOR
• HOST FINIDING BEHAVIOUR
• OLFACTORY PARTS AND TISSUES
• ROLE OF CARBONDIOXIDE IN HOST SEEKING
BEHAVIOUR
• ROLE OF SWEAT AND BODY ODOUR IN HOST SEEKING
BEHAVIOUR
• ROLE OF VISION IN HOST SEEKING BEHAVIOUR
• ROLE OF TEMPERATUE IN HOST SEEKING BEHAVIOUR
• ROLE OF HOST MARKING PHEROMONE
• EXPERIENCE IMPACTS ON FUTURE HOST CHOICE IN
MOSQUITOES

3. What is meant by behavior ?
• Behavior is the action and the mannerisms made
by individuals, organisms, systems or artificial
entities in conjunction with themselves or their
environment, which includes the other systems or
organisms around as well as the physical
environment. (Hoy, M. A. 2013)
For example : FORENSIC ENTOMOLOGY –
Blow flies, beetles, and other bugs flock to
decomposing remains to feed, lay eggs or prey on
other at the scene. This particular behavior of these
insects can enable us to estimate the time since
death

4. Classification of behavior
Learned behavior: Innate behavior:
• Acquire new skills and
knowledge through trial and
error, observation of other
individuals, or memory of past
events.
• Example: mosquitoes develop
resistance against certain
pesticides.
• It is the naturally behavior in
all members of a species and it
is controlled by genes with
little or no environmental
effect because first behaviors
in entirely innate.
• Example: new born nymph or
larva has no prior experience
adult actively seek the habitat
that it has experienced as a
young. This phenomenon is
called hopkin’s host
selection principle.

5. Various types of behavior exists in mosquitoes and
sandflies
• Resting behavior (endophilic or exophilic)
• Mating behavior (time of mating - dawn or dusk)
• Host – seeking behavior (zoophagic or
anthropophagic)
• Biting behavior (diurnal or nocturnal)
• Gonotrophic behavior (medium for oviposition-
fresh water or polluted water)

7. Purpose of studying the behavior of mosquitoes and
sandflies:
• Mosquitoes transmit pathogens that cause
disease such as dengue, yellow fever, filariasis
and most significantly human malaria.
• The dual receptor designed as cpA (Gr 1,2,3) of
maxillary palp of mosquito of CO2 and skin-
odorants as a key target that could be useful to
disrupt host-seeking behavior and thus aid in
the control of disease transmission.

8. host finding behavior
• Host seeking behavior of blood feeding insects
find host from a distance.
• At the greater distance, visual and olfactory clues
are involved.
• For the short distance, body temperature, CO2
and moisture are important.
• Almost all hematophagous insects respond to
CO2 and some kairomones released by host.
• Specific CO2, receptors located on the maxillary
palps and lactic acid sensitive receptors on the
antennae. (Takken, W. 1991)

9. Olfactory parts and tissues of mosquitoes and sandflies
• The antenna, maxillary palp
and the labellum are the three
major sensory organs.
• The ability of mosquitoes to
identify a host for a blood meal
or a correct site where to lay
eggs via olfactory cues is
conferred by a rich repertoire
of Odorant Receptors (ORs)
expressed in olfactory sensory
neurons (OSNs) housed in the
olfactory sensilla. (Zhou et
al., 2014).

11. • Peristimulus-time histograms: each panel
reports a peristimulus-time histogram
illustrating the temporal dynamics of the
responses to each odor. In each panel, point 0
indicates the onset of the 0.5 sec odorant
stimulus. The olfactory responses were assayed
as firing rates in consecutive 50 ms intervals
beginning 1 sec before the odor stimulus and
continuing for another 1 sec.

13. ROLE OF CARBON DIOXIDE:
• With regard to host location, female mosquitoes
hunt their blood host by detecting organic
substances produced from the host. They can
sense carbon dioxide and lactic acid up to
100 feet (36 meters) away.
• Mammals and birds gives off CO2 as part of
their normal breathing.
• Because CO2 is present in the atmosphere,
mosquitoes respond to higher-than-normal
concentrations, especially when the CO2 is
mixed with host-odor.

14. • Some studies indeed shows that an odorous
blend consisting of ammonia, lactic acid, and
two other carboxylic acids is almost as attractive
to mosquitoes and sand flies as an extract of
human skin residues.
• A more complex blend of CO2, ammonia, lactic
acid, and seven other carboxylic acids attracts
three to five times more mosquitoes and
sandflies into experimental huts than sleeping
humans.

16. ROLE OF SWEAT AND BODY ODOUR:
• Variation in sweat
composition causes
differential attractiveness to
mosquitoes between humans
and other mammals and
between individuals.
• Characteristics of skin
glands and skin microbiota
define the odorous organic
compounds emitted by sweat,
thereby the degree of
attractiveness of the host to
mosquitoes.
• Carboxylic acids in
particular appear to
characterize humans.

17. • Eccrine glands are the best developed and most
abundant glands in humans and are widely
distributed over the general body surface. By
contrast, in most mammalian groups such as
cattle's eccrine glands are limited to the friction
surfaces of the leg, feet and tail.
• Apocrine glands, which play an important role in
chemical communication, have a restricted
distribution in most mammals including humans.
• The microbiota composition on human skin is
determined mainly by the number and density of
apocrine, eccrine, and sebaceous glands at a
specific site and whether or not the site is shielded
from direct contact with the surrounding air.

18. ROLE OF VISION :
• Mosquitoes use sight as their
second method of detection.
• They have compound eyes
distinctly separated from one
another. Eyes have many
separate visual units called
ommatidia.
• Each ommatidium contains
a lens and a light-sensitive cell.
(Land et al., 1999; Hu et
al., 2014; Hu et al., 2009)

19. • Eyes of this design allow for the detection of
small movements, but are weak in
distinguishing detail (mosquitoes pick up
movement which indicates a likely living target).
• In the spherical arrangement of their compound
eyes, blind spots separate each eye from the next
one. As a result, they can't see a human being until
they are 30 feet (10 meters) away. (Hu et al.,
2014; Moon et al., 2014; Rocha et al., 2015).
• Even then, they have trouble distinguishing objects
of similar size and shape. When they are 10 feet (3
meters) away they use extremely sensitive thermal
receptors on the tip of their antennae to locate blood
near the surface of the skin.

20. • The range of these receptors increases threefold
when the humidity is high (in mosquito habitat
such as forests or wetlands).
A mosquito’s sight is also based on color.
• A mosquito sees the contrast between the color
of clothing and that of a person's skin. If you are
wearing clothing that contrasts with the
background, and especially if you move while
wearing that clothing, mosquitoes can see you
and zero in on you.

21. ROLE OF TEMPERATURE:
• Heat sensitivity is a sensory modality that
plays a critical role in close-range host-
seeking behaviors of adult female.
• An essential step in this activity is the ability to
discriminate and respond to increases in
environmental temperature gradients through the
process of peripheral thermoreception which is
provided by a set of distal antennal sensory
structures.
• Recent behavioral studies, however, have indicated
that heat alone has no effect on the mosquitoes and
sandflies response, but significantly synergizes the
attraction to the host odor.

22. • Thermoreception is the
process by which
different level of heat
energy in the
environment and or in
the body is detected by
the organisms for various
purposes.
• In insects such as
mosquitoes and sandflies
humidity and
temperature receptors
usually present in the
single sensillium.

23. ROLE OF HOST MARKING PHEROMONE
• A marking pheromone is a chemical compound
(or mixture of compounds) emitted by an insect
that advertises the past or current presence of
the insect or its progeny at or in association with
a valued resource. The type of resource may be
food, an egglaying site, or a site of shelter.
• Marking pheromones may be released from a
variety of endocrine or exocrine glands of insects
as well as from other structures associated with
digestive, reproductive and locomotory systems.

24. Experience impacts on future host
choice in mosquitoes
• Evidence from epidemiological studies suggests
that mosquitoes can ‘learn’ from experience.
• Sensory cues can differ from one individual to
another, such as different humans emitting different
odor profiles.
• If a mosquito bites an individual with a certain odor
profile and has a positive experience, it might learn
to associate that odor profile with a high-quality
blood meal. Subsequently, it will choose to bite
those individuals with similar odor profiles, here
depicted in different colors. (Woolhouse et al.,
1997)

25. Experience impacts on future host
choice in mosquitoes

26. FACTORS INFLUENCING HOST SEEKING
BEHAVIOUR

27. REFERRENCE:
• https://doi.org/10.1098/rsos.170189
• Hoy, M. A. et al 2013
• Takken, W. et al 1991
• https://www.slideshare.net/farwafayaz1/thermorec
eption-in-insects
• https://link.springer.com/referenceworkentry/10.1
007%2F978-1-4020-6359-6_1730
• https://jeb.biologists.org/content/221/4/jeb157131
• (Hu et al., 2014; Moon et al., 2014; Rocha et al.,
2015; Hu et al., 2009 ;Land et al., 1999).
• Woolhouse et al., 1997.