For educational purposes:--
Information on the basics of Entomology
Entomology: ODONATA 1
Kingdom: Animalia, Phylum: Arthropoda
Subphylum: Hexapoda: Class: Insecta: Order: Odonata
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Odonata -- <Adults> & <Juveniles> -- are predacious insects with biting mouthparts. They have two similar pairs of wings with characteristic reticulate venation; prominent eyes and small antennae. The abdomen is elongated with accessory male genitalia on the 2nd and 3rd sterna. The metamorphosis is Hemimetabolous, the naiads are aquatic and they have a modified labium known as the mask.
Fossil Record. -- Specimens date back to over 250 million years. Although present day forms have a wingspread of about 13 cm, extinct forms had a 3/4 meter wingspread.
Body Form. -- They are all large insects, and in the Carboniferous period genera existed which had a wing expanse of two feet. They are strong and rapid fliers, catching their food, in the form of small insects, on the wing. The forwardly directed legs play an important part in catching the prey and holding it while it is chewed.
All the mouth appendages are toothed, and the maxillae and labium augment the mandibles in chewing capacity unlike most insects with biting mouthparts. The compound eyes of Odonata are the largest of all insects.
Mating. -- The process is quite unique for insects. Although the male pore is on segment 9 of the abdomen, the copulatory apparatus is found in the sternal region of segments 2 and 3. Before copulation, spermatozoa are transferred to this structure. The male then grasps the female in the region of the prothorax by means of his posterior abdominal claspers. While in flight in this tandem position the female turns her abdomen down and forwards and receives sperm from the accessory copulatory structure of the male.
Oviposition. -- Dragonfly eggs are laid in water or on waterweeds. The naiads breathe with tracheal gills and are of two kinds: (I) those with external gills in the positions of cerci anales and caudal filaments and caudal filaments-Zygoptera, (2) those with gills on the walls of the rectum- Anisoptera. In the latter case water is pumped in and out through the anus, and this action may be made use of in locomotion-the sudden expulsion of water causing a rapid forward movement on the part of the naiad. However, the naiads on the whole slow-moving creatures, lurking well camouflaged among waterweeds while in wait for their prey. The main difference between the mouthparts of the naiad and imago concerns the labium. In the adult this has normal proportions, but in the naiad the post- mentum and prementum are elongated and capable of being shot out rapidly from the folded resting position, thereby impaling the prey, e.g., a tadpole, on the labial hooks.