1. ARDHI UNIERSITY
SCHOOL OF ENVIRONMENTAL SCIENCE AND
TECHNOLOGY
DEPARTIMENT OF ENVIROMENTAL ENGENEERING
NAME;RAPHAEL, GLORIA B.
REG;1689/T2009
ASSIGMENT NO 1
Qn; Write on the life cycle of the following , mosquitoes, cockroach, lice,ascaris
lumbricoides,hookworm and rat.

2. LIFE CYCLE OF MOSQUITOES
Mosquitoes are both intermittent parasites and ectoparasites. There immature stages eggs, larvae
and pupae are all aquatic that is they all live in water. The adult mosquitoes on other hand are
terrestrial they live in dry land. All mosquitoes must have water in which to complete their life
cycle. This water can range in quality from melted snow water to sewage effluent and it can be in
any container imaginable. The type of water in which the mosquito larvae is found can be an aid
to the identification of which species it may be. Also, the adult mosquitoes show a very distinct
preference for the types of sources in which to lay their eggs. They lay their eggs in such places
such as tree holes that periodically hold water, tide water pools in salt marshes, sewage effluent
ponds, irrigated pastures, rain water ponds, etc. Each species therefore has unique environmental
requirements for the maintenance of its life cycle.
Most female mosquitoes have to feed on an animal and get a sufficient blood meal before she
can develop eggs. If they do not get this blood meal, then they will die without laying viable
eggs. However, some species of mosquitoes have developed the means to lay viable eggs without
getting a blood meal.
The length of life of the adult mosquito usually depends on several factors: temperature,
humidity, sex of the mosquito and time of year. Most males live a very short time, about a week;
and females live about a month depending on the above factors.
Mosquito Life Cycle

3. The mosquito goes through four separate and distinct stages of its life cycle and they are as
follows: Egg, Larva, pupa, and adult. Each of these stages can be easily recognized by their
special appearance. There are three common groups of mosquitoes living in the Bay Area.
They are Aedes, Anopheles and Culex . Aedes transmit yellow fever, Anopheles transmit malaria
and filariasis and Culex transmit filariasis.
Eggs are laid one at a time and its depend to the type of genera of mosquito Culex, and
Anopheles lay their eggs on water while Aedes lay their eggs on damp soil that will be flooded by
water. Most eggs hatch into larvae within 48 hours.
Larva : The larva live in the water and come to the surface to breathe. The larva feed on micro-
organisms and organic matter in the water. On the fourth molt the larva changes into a pupa.
Pupa: The pupal stage is a resting, non-feeding stage. This is the time the mosquito turns into an
adult. It takes about two days before the adult is fully developed. When development is
complete, the pupal skin splits and the mosquito emerges as an adult.
Adult: The newly emerged adult rests on the surface of the water for a short time to allow itself
to dry and all its parts to harden. Also, the wings have to spread out and dry properly before it
can fly.
LIFE CYCLE OF COCKROACH
Cockroach are organism who are attracted to human excreta in the latrines where as they find
moisture and food for there survival and growth. They eats both food and faeces of human being
and domestic animals. By feeding on infected faeces and later on food cockroach contaminate
the food and hence transmit diseases.
The cockroach undergo four stages which is egg, nymph one and two then the adult one.

4. They prefer to live in close association with there food and in dark place in order to obtain water
and food. In most time cockroach move from sewers into homes and carries faeces on their
bodies,legs or in their gut.They transmit typhoid bacteria, cholera, dysentery and enteric virus.
The best way of there control is by protection of food and an emproved domestic sanitation.

5. LIFE CYCLE OF LICE
Head lice are insects that feed off the of the blood of their host. One louse can produce hundreds
of eggs during its lifespan. Head lice live for nearly two months and have three stages of life. A
mature or adult head louse can lay up to 10 eggs or nits each day. These nits, or lice eggs, hatch
in about 7 to 12 days. Baby lice or nymphs are about the size of a pinhead when they hatch, and
quickly mature into adult lice in about 9 to 12 days. In just a few days, adult lice are ready
mate, starting this lice life cycle all over again during their 3 to 4 week lifespan.
Nits are laid by female lice at the base of the hair shaft. Once laid, nits take five to 10 days to
hatch. Eggs, which are about the size of sesame seeds, are yellowish-brown to white in color.
When the nits hatch, they release nymphs.
Nymphs look like adult lice, but are smaller in size. Nymphs molt (outgrow their exoskeleton)
three times before becoming an adult. The nymph stage lasts up to seven days.
The adult is the third stage of head lice. Adults can live up to 30 days and feed off the host up to
five times a day. Adult females will lay up to a dozen eggs a day.

6. Lice are often transmitted from host to host via objects that come in contact with hair. Head lice
can go two or three days without feeding and can live on detached hair strands, clothing, hats,
combs, towels and bedding.

7. LIFE CYCLE OF ASCARIS LUMBRICOIDES
Are also known as round worms of man. Is the largest of the intestinal nematodes parasitizing
humans. It is the most common worm found in human. It is worldwide in distribution and most
prevalent through out the tropics, sub-tropics and more prevalent in the countryside than in the city.
The adults are cylindrical in shape, creamy-white and pinkish in color. The female averages
20~35cm in length, the largest 49cm. The male is smaller, averaging 15~31cm in length and
distinctly more slender than the female. The typical curled tail with a pair sickle like copulatory
spine readily distinguishes males. On the tip of the head there are three lips, arranged as a Chinese
word “ 品 ”. They have a complete digestive tract. Reproductive organs are tubular. male has a
single reproductive tubule. The female has two reproductive tubules and the vulva is ventrally
located at the posterior part of the anterior 1/3 of the body. There are three kind of the eggs. They
are fertilized eggs, unfertilized eggs and decorticated eggs. We usually describe a egg in 5 aspects:
size, color, shape, shell and content.
Fertilized eggs: broad oval in shape, brown in color, an average size 60 x45µm . The shell is
thicker and consists of ascaroside, chitinous layer, fertilizing membrane and mammillated
albuminous coat. The content is a fertilized ovum. There is a new-moon shaped space at the each
end inside the shell.
Unfertilized egg: Longer and slender than a fertilized egg. The chitinous layer and albuminous coat
are thinner than those of the fertilized eggs without ascaroside and fertilizing membrane. The
content is made of many refractable granules various in size.
Decorticated eggs: Both fertilized and unfertilized eggs sometimes may lack their outer albuminous
coats and are colorless. .
Life Cycle
1. Site of inhabitation: small intestine
2. Infetive stage: embryonated eggs
3. Route of infection: by mouth

8. 4. No intermediate and reservoir hosts
5. Life span of the adult: about 1 year
LIFE CYCLE OF HOOKWORMS
Hookworm is the second most common human helminthic infection (after ascariasis).
Hookworm species are worldwide in distribution, mostly in areas with moist, warm
climate. Infection of the host is by the larvae, not the eggs. While a duodenal can be ingested, the
usual method of infection is through the skin; this is commonly caused by walking barefoot
through areas contaminated with fecal matter. The larvae are able to penetrate the skin of the
foot, and once inside the body, they migrate through the vascular system to the lungs, and from
there up the trachea, and are swallowed. They then pass down the esophagus and enter the
digestive system, finishing their journey in the intestine, where the larvae mature into adult
worms
The cycle
Once in the host gut, Necator tends to cause a prolonged infection, generally 1–5 years (many
die within a year or two of infecting), though some adult worms have been recorded to live for
15 years or more. On the other hand, Ancylostoma adults are short lived, surviving on average
for only about 6 months. However, infection can be prolonged because dormant larvae can be
"recruited" sequentially from tissue "stores" (see Pathology, above) over many years, to replace

9. expired adult worms. This can give rise to seasonal fluctuations in infection prevalence and
intensity (apart from normal seasonal variations in transmission).
LIFE CYCLE OF RAT
Rats are born in a nest, in a litter of 6-8 young. The nest is often in a secure place with nesting
debris such as in an attic in the insulation. They are born tiny and hairless (pinkies), with eyes
sealed shut. After two weeks of nursing, their eyes open, and within 4 weeks, they are weaned.
After three months of life, they are independent and on their own, although they typically use the
same habitat as their birthplace (i.e. they live in the same home or attic).
Small rats after born
Rats don't live particularly long in the wild. Like all rodents, they rely upon breeding in high
numbers and eating a lot and growing quickly. In this respect, they are somewhat like insects,
and thus can sometimes swell to large numbers given the right conditions. In normal
circumstances, disease and predators keep their numbers in check. Rarely do rats live for more
than a year in the wild. During that year, however, they can create a lot of new rats and a
Rats don't live particularly long in the wild. Like all rodents, they rely upon breeding in high
numbers and eating a lot and growing quickly. In this respect, they are somewhat like insects,
and thus can sometimes swell to large numbers given the right conditions. In normal
circumstances, disease and predators keep their numbers in check. Rarely do rats live for more
than a year in the wild. During that year, however, they can create a lot of new rats and a lot of
damage. Just one adult female can create more than 40 new rats in a year. In their lifetime, rats

10. tend to stick to familiar territory.
They are not explorers. They find an area that suits their needs, with shelter and food (human
homes and attics quite often fit the bill) and rarely venture more than a few hundred feet from
that area. They rarely die naturally, but when they do, it's often in safe place like your attic, and
you'll notice the smell. Most will be killed by predictors.
Cycle of rat.