1. Phylum: Arthropoda
Arthropods are segmented coelomates with exoskeletons (cuticle) and jointed appendages.
This phylum is represented in nearly all habitats in the biosphere.
Arthropods are regarded as the most successful animal phylum.
The diversity and success of arthropods is largely due to three features:
- body segmentation تعقل الجسم
- a hard exoskeleton جليد خارجي صلب
- jointed appendages زوائد مفصلية

2. The body of an arthropod is completely covered by the cuticle, an exoskeleton constructed from layers of protein and chitin.
The exoskeleton of arthropods is strong and relatively impermeable to water.
Arthropods have well-developed sense organs, including eyes for vision, olfactory receptors for smell, and antennae قرون استشعار for touch and smell.
Have sensory antennae and usually a pair of compound eyes in addition to simple eyes.
Arthropods have an open circulatory system in which hemolymph fluid is propelled by a heart through short arteries.
Arthropods have evolved a variety of specialized organs for gas exchange.

4. 1- Class: Arachnidaطائفة العنكبيات
These include scorpionsالعقارب , spidersالعناكب , ticksالقراد , and mitesالحلم .
They have four pairs of walking legs.
Nearly all ticks are blood-suckingماص للدماء parasites on the body surfaces of most animals.
In most spiders, respirationالتنفس is carried out by book lungsالرئة الكتابية .

5. 2-class: Insectaطائفة الحشرات
They live in almost every terrestrial (earthly) habitat and in fresh water, and flying insects fill the air.
The study of insect, (Entomology) is a vast field with many subspecialties, including physiology, ecology, and taxonomy….etc.
Class Insecta is divided into about 26 orders.
Many insects have one or two pairs of wings that emerge from the dorsal sideظهري of the thoraxالصدر.
They have three pairs of legs.

6. The Insects:
750,000 + species insects described, but may be 30 million species undescribed.
Many adaptations make insects one of the most successful terrestrial animals.
Exoskeleton for water conservation.
Tracheal System for gas exchange.
Metamorphosis.
Many types of mouth parts.
Flight.

7. In the complete digestive system, there are regionally specialized organs.
Metabolic wastes are removed from the hemolymphالدم by Malpighian tubulesأنابيب ملبيجي , out pockets of the digestive tract.
Respiration is accomplished (done) by a branched, chitin-lined tracheal systemالجهاز القصبي that carries O2 from the spiraclesفتحات تنفسية directly to the cells.
The insect nervous system consists of a pair of ventral nerve cordsحبلين عصبيين بطنيين with several segmental ganglia.

8. رأس
صدر
بطن
قرون استشعار
عين مركبة
Fig

9. 3 Kinds of Insect Metamorphosis
Ametabolous Metamorphosis: (بسيطة او عديمة التحول)only difference between larvae and adult are size; both are wingless.
Hemimetabolous (Incomplete) Metamorphosis: (ناقصة التحول)develop from egg to adult has several stages with smaller versions of adults called nymphs. Immature nymphs have no wings or genitalia until adult.
Holometabolous (complete) Metamorphosis: (كاملة التحول)after hatching from egg, immatures (غير ناضج)are called larvae (very different body form than adult). After several instars(stage of development), the last larval molt forms a pupa – undergoes radical body form change.

10. Incomplete or Hemimetabolous Metamorphosis

11. Complete or Holometabolous Metamorphosis

12. You Decide?
Fig