The classes in Phylum Arthropoda: class crustacea, class diplopoda, class arachnida, class chilopoda, class insecta and class merostomata

1. Phylum
Arthropoda
Class
Crustacea
(lobster, prawn,
barnacles, crabs)
Class
Chilopoda
(centipedes)
Class
Diplopoda
(milipedes)
Class Insecta
(grasshopper,
cockroach)
Class
Arachnida
(Spider, ticks, mites,
scorpions )
Class
Merostomata
(only 3 genera of
horseshoe crabs )
Reproduction
(Example: common
cockroach
Periplaneta)

2. Class Merostomata
The body are protected by a hard
shell, divided into a cephalothorax and
abdomen
Bear six pair of appendages, the
chelicerae, pedipalps and four pairs of
walking legs.
They live in deep water and feed on
molluscs and annelids.
Considered living fossils –structure
has remained basically unchanged for
the last 300 million years
Pedipalp
Limulus sp.
(horseshoe crabs)

3. Class Chilopoda
Clearly defined head with a pair of antennae
and a pair of mouthparts.
The elongated body consists of numerous
segments. Each segment bears a pair of similar
appendages.
Eyes are simple, compound or absent
 Carnivorous and feed mainly on insects, which
they capture and kill using poison fangs on first
segment after the head
Maxilliped (poison claw)
Lithobius sp.
(centipede)

4. Class Diplopoda
The body segments bear two pairs of
legs each. Each segment also has glands
which secret a foul- smelling liquid
which protects them from attack.
Most are herbivores that feed on live or
decaying vegetation. They play an
important role in the detritus food chain.
Lulus, common millipede

5. Class Arachnida
•Body are divided into cephalothorax (prosoma)
and abdomen (opisthosoma)
•4 pairs of walking legs n simple eyes.
•No antennae, the function of antennae is
performed by numerous sensory hairs which
cover the body and appendages.
•*Have a pair of chelicerae (fangs or pincers)
which are often connected to a poison gland.
•*Have a pair of pedipalps ( second pair of
appendages) which may used to hold food, act
as sensory organ of taste or as pincers to
capture prey.
•Mostly are carnivores that feed on other
arthropods especially insects, which they will
digest externally before ingesting it.
Lycosa
( spider)

6. Class Insecta Have clearly defined head,
thorax, abdomen, a pair of
antennae , 3 pairs of mouthparts. 3
pairs of legs each thoracic segment
with a pair of legs), a pair of
compound eyes and simple eyes.
Adults have one or two pairs of
wings.
Locusta, an insect
The life cycle of insects is characterised
by several moults. The stage between two
consecutive moults is called an instar
Some insects show incomplete
metamorphosis, that is, the eggs hatch
into nymphs which resemble the adults in
most ways, except that they lack wings
and are sexually immature. After the last
moult, the adult (imago) emerges.
There are four distinct stages in
complete metamorphosis :
egg larva pupa imago
The larvae are morphologically,
physiologically and behaviourally different
from adult.

7. Class CRUSTACEA
They have a cephalothrorax whereby the
head is not clearly distinct from the thorax.
They have 2 pairs of antennae , at least one
three pairs of mouthparts (jaws), a pair of
compound eyes raised on stalks.
They have appendages on their abdomen as
well as on their thorax. The appendages in
different parts of the body are specialised to
perform different functions: feeding,
locomotion, reproduction and sensory
structure.
They lack a waterproof exoskeleton.
They use gills which are outgrowths of the
body wall or limbs for gaseous exchange.
Have separate sexes. The male use s
specialised appendages to transfer
sperm to the female. Fertile eggs may
be carried on the body. When the eggs
hatch, they develop into nauplius
larvae which is the characteristic larval
form of all crustaceans. The larvae go
through a number of moults before
reaching maturity.
Penaeus sp.
(prawn)

8. Male and female cockroach
(Clasper)
The male
cockroach has
a pair of
claspers that
grasp the
female during
copulation.
The number of visible segments is higher
in the male than the female. Also the
females posterior abdomen is broader
and more rounded than the male

9. Reproduction system of male cockroach
A pair of testes to produce
sperm
Vas deferens
Seminal vesicles
Ejaculatory duct
Penis
**Accessory gland secret fluid
that is mixed with the sperm
before ejaculation.
Vas
deferens

10. Reproduction system of female cockroach
A pair of ovaries, each made
up of eight ovarioles which
produce ova.
Oviducts
Vagina
** Accessory glands secrete
chemical to make the
ootheca, an egg sac.
** Spermathecal connected
to vagina, which store the
sperm ejaculated from the
male cockroach during
mating.

11. 1. During mating, The tips of the abdomens are held
close together, then a package of sperm wrapped
in a protein capsule is inserted into the vagina of
the female by means of extensible penis
2. When the insect separate, the spermatophore
ruptures and the sperm swim to the
spermatheca.
3. After mating, ova are passed down the vagina
and fertilised by the sperm in the spermatheca.
4. The fertilised eggs are carried in ootheca . It is
carried to the insect for a few days before it is
shed, usually in dark place.
5. When the ootheca breaks after
about six weeks, the young
nymphs emerge.
**Cockroach shows
Hemimetabolous development
(insect development in which
there is incomplete or partial
metamorphosis, typically with
successive immature stages
increasingly resembling the
adult)

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