The phylum Arthropoda contains a wide diversity of animals with hard exoskeletons and jointed appendages. Many familiar species belong to the phylum Arthropoda—insects, spiders, scorpions, centipedes, and millipedes on land; crabs, crayfish, shrimp, lobsters, and barnacles in water.

1. Shri Shivaji Education Society, Amravati's
Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly. Dist. Buldana
Topic: Phylum Arthropoda
Class: B.Sc-I, Sem-I
Shantaram Bhoye
Assistant Professor & Head
Department of Zoology
M.Sc., NET-JRF, SET, M.A.(Eng.)

2. Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana
Phylum: Arthropoda
 Arthropoda is the largest phylum with about nine lakh species.
 They may be aquatic, terrestrial or even parasitic.
 They have jointed appendages and a chitinous exoskeleton.
 This phylum includes several large classes and contains the class Insecta which itself
represents a major portion of the animal species in the world.
 They possess the ability to survive in every habitat.

3. Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana
Arthropoda Characteristics
The arthropoda characteristics are mentioned below:
1.The body is triploblastic, segmented, and bilaterally symmetrical.
2.They exhibit organ system level of organization.
3.The body is divided into head, thorax, and abdomen.
4.Their body has jointed appendages which help in locomotion.
5.The coelomic cavity is filled with blood.
6.They have an open circulatory system.
7.The head bears a pair of compound eyes.
8.The exoskeleton is made of chitin.
9.The terrestrial Arthropods excrete through Malpighian tubules while the aquatic ones excrete through green glands or
coaxal glands.
10.They are unisexual and fertilization is either external or internal.
11.They have a well-developed digestive system.
12.They respire through the general body surface or trachea.
13.They contain sensory organs like hairs, antennae, simple and compound eyes, auditory organs, and statocysts.

4. Classification:
Kingdom : Animalia
Phylum : Arthropoda
Class : Insecta
Superorder : Dictyoptera
Order : Blattodea
1) Habit and Habitat of Cockroach:
 Cockroach prefers to live in damp but warm places and generally found in kitchens, hotels, bakeries,
restaurants, warehouses, grocer’s shops, sewage, ships and public latrines, etc., where plenty of food
is available.
 It is a nocturnal animal hiding in holes and crevices during the day and coming out at night when it
tastes diverse objects like clothes, shoes, books and human food to feed upon.
 Thus, it is omnivorous in diet.
 It is a fast runner, i.e., cursorial in habit.
 It can also fly but it flies very rarely.
 It is dioecious and oviparous and exhibits parental care.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

5. 2. External Features of Cockroach:
a) Shape, Size and Colour of Cockroach:
 Its body is narrow, elongated, compressed dorsoventrally and bilaterally symmetrical.
 The adult cockroach measures from 2 to 4 cm in length and about 1 cm in width.
 The colour is reddish-brown.
 There are two dark patches surrounded by a light-brown margin in the first thoracic segment.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

6. (b) Exoskeleton:
 The entire body of cockroach is covered by a hard, brown-coloured exoskeleton.
 The exoskeleton of each segment has four separate sclerites which are joined together by
delicate and elastic articular membrane.
 The sclerites of the dorsal side are called tergite, of ventral side are called sternite and those of
lateral sides are called pleurites.
 The exoskeleton, in fact, consists of a thick and strong chitinous cuticle which provides
protection to the body, prevents unnecessary water loss and points for the attachment of
muscles.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

7. (c) Segmentation:
It shows clear cut segmentation in its body except the head.
The thorax consists of three segments and abdomen ten segments in adults which were eleven in embryo.
The head is said to be formed by the fusion of six embryonic segments.
However, the total body segments in embryo remain twenty but in adults only nineteen.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

8. (d) Division of Body:
 Its body is clearly divisible into three regions, i.e., head, thorax and
abdomen.
Head:
 It is ovate and flattened antero-posteriorly region.
 It is highly mobile in all directions due to a flexible neck.
 The head bears a pair of compound eyes, a pair of antennae and
appendages around the mouth.
 Each antenna has three parts, a large basal scape, followed by a smaller
pedicel and a long filamentous, many-jointed flagellum.
 Such an antenna is called filiform antenna.
 The antennae possess small sensory bristles and it can be moved in all
possible directions.
 The antenna belongs to the second segment of the head.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

9. Mouth parts:
 The appendages around the mouth constitute the mouth parts which are of chewing or
mandibulate or orthopterus type.
 The mouth parts consist of a labrum, a pair of mandibles, a pair of maxillae, a labium
and a hypo-pharynx.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

10. 1. Labrum:
 It is movable due to the muscles inserted on its base.
 It lies in front of the mouth as the upper lip.
 On its ventral surface many sensory setae are situated which are possibly
gustatoreceptors.
 Fused to the inner surface of labrum is a thin membranous plate, called the
epipharynx.
2. Mandibles:
 The mandibles are jaws used for crushing and cutting the food.
 The mandibles are movable with the help of adductor and abductor sets of muscles.
 The contraction of adductor muscles brings the mandibles closer so that their teeth are
inter-fitted and in this position the food is broken down into small fragments.
 Then the abductor muscles contract and the mandibles get separated from
each other.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

11. Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana
3. Maxillae:
 These are two, one on either side of the
head.
 Lacinia which is a flat, tapering lobe
ending in two sharp claw-like projections,
its inner margin bears stout bristles.
 The maxillae hold food by the claws of
the lacinia and bring it to the mandibles
for mastication.
 The maxillae are also used for cleaning
the antennae, palps and front legs.
 The maxillae belong to the fifth segment
of the head.

12. 4. Labium:
 It represents the lower lip of the cockroach and covers the mouth from the ventral side.
 It is also known as the second maxillae as it is supposed to be formed by the fusion of two
maxillae.
 It is made of two basal chitinous plates, mentum and sub-mentum.
 It helps to hold food in place when the insect feeds.
5. Hypo pharynx:
 Between the maxillae and in front of the labium is flat cylindrical structure called the hypo
pharynx or lingua.
 The common salivary duct opens at the base of the hypo pharynx.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

13. Neck:
 The neck or cervicum is a slender soft region supported by chitinous cervical plates, two dorsal
and two ventral.
 The neck has muscles which retract and protract the head and turn it up or down or from side to
side.
 The cockroach can also stretch its head like other insects.
Thorax:
 The thorax consists of three segments, the prothorax, mesothorax and metathorax.
 Each segment bears a pair of walking legs and the first pair of wings arise from the mesothorax,
while the second pair from the metathorax.
 The prothoracic segment is the largest and due to the presence of three pairs of walking legs it is
also called hexapoda.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

14. Walking legs:
 All the three pairs of walking legs are similar and they help
the cockroach in its cursorial (fast running) habit.
 Each leg consists of five segments—a large basal coxa, it is
followed by a smaller trochanter which is freely movable
on the coxa but is fixed to the next segment, the femur
which is long and broad; this is followed by a long
uniformly thick tibia which bears stout bristles, the known
as tibial spurs; the last segment is a tarsus having five
movable joints or podomeres or tarsomeres which have
five bristles, and their lower sides have soft adhesive pads,
the plantulae.
 Between the claws is a soft hollow lobe, the arolium having
small bristles.
 The arolium is an adhesive organ for holding on the smooth
surfaces.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

15. Wings:
 The wings are two pairs, the first pair arises
from mesothorax and second pair from
metathorax.
 The first pair of wings are heavily sclerotized
and are known as elytra or tegmina.
 These are protective and cover the hind wings
in a folded state, the left tegmen partly
overlaps the right.
 The second pair of wings are membranous
and larger, they lie folded below the tegmina
when at rest.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

16. Abdomen:
 Abdomen consists of ten segments.
 The exoskeleton of the abdomen is formed of
hardened sclerites.
 A typical abdominal segment has a dorsal
tergum, ventral sternum and between them a
narrow membranous pleuron on each side.
 The genital apertures of both sexes are
surrounded by sclerites called gonapophyses.
 In the male, the gonapophyses belong to the 9th
segment and they form the external genital
organs or external genitalia.
 In female the gonapophyses belong to the 8th
and 9th segments and they form an ovipositor.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

17.  The membrane between the 5th and 6th abdominal terga forms two deep pockets in the male,
each pocket has two slit-like pouches which are probably glandular and produce a secretion
which excites the female for copulation in the breeding season.
 These are called stink glands.
 Some workers suggest that the secretion of these glands possesses a characteristic odour which is
probably repulsive for the enemies and helps the female in detecting the presence of its mate.
 The male genital aperture is situated between the 9th and 10th sterna, while the female genital
aperture is situated on the 8th sternum.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana

18. Spiracles:
 There are ten pairs of slit-like spiracles, two on the thorax and eight on the abdomen.
 The first pair of thoracic spiracles lies on the pleuron between the pro-thorax and metathorax
and the second pair lies between the mesothorax and metathorax.
 The first pair of spiracles being larger than the other.
 Abdominal spiracles are smaller than the thoracic ones.
 These are the exits of respiratory system.
Mr. Shantaram Bhoye, Assistant Professor, Shri Pundlik Maharaj Mahavidyalaya, Nandura Rly., Dist. Buldana