Abdominal appendages & genitalia:
The abdomen of adult insect represents a large hint techma of the body bearing no signal paired appendages except the cerci, style & external genitalia.
Each abdominal segment of insect embryo bears a pair of rudimentary appendages but most of them disappear during post embryonic development. The adult insect particularly pterygotes have the appendages mostly on some posterior segment of the abdomen, a pair of cerci. On the XI segment & genitalia on the segment 8 & 9 in female & only 9 in male. The segment of this called genital segment. The segment pair to 8 are Pregenital segment which are in adult pterygotes devoid of any appendages. In pterygotes an immature pterygotes various pregenital
appendages are seen. The 11 segment of some insects bear a pair of appendages, the cerci.
Which may be consider post genital appendages.
1) Pregenital Appendages: the vertical tube of the adult Collembola is formed due to a fussion of paired appendages of embryotic segment I of abdomen. Similarly, adult protura & Diptura also bear a pair of 1st abdominal segment. They though occur as pair glandular appendages & commonly termed as the pleuripedia on the abdominal segment 1 of embryo. They disappear
completely in the Thysanura pterygota with the post embryonic development. Similarly,
segments 2-7 bear paired appendages as legs the larva of Pneumonia. Sialis & Sisyra & in addition serve that secondary function of the tracheal gills. Similar type of structure are also found in the larva of some Mecoptera, Hymenoptera & Lepidoptera. In which they developed
into larvel legs known as pseudopods. In Apterygota , however they are continue to few segments & are widely modified.
2)Genital appendages-Genitalia: The genital segments 5-10k in male n 8th & 9 in female bears a group of appendages commonly called genital organs & the constitute well defined male &
female external genitalia. They are involved in the mechanism of population & perform sperm transfer & oviposition in male n fe. Respectively.
The main genital organ in male penis while in female is ovipositor and other are accessory genital organs. A/C Snoolgrass 1935 accessory genital organs can be defferentiated into 2 types._ Median intromittent apparatus called the phallic organ & the other group the peripheral
accessory structures are called the periphallic organs. The phallic org. Are involved in coitus while the periphallic organs are formed the fun. Of folding or grapping the female during copulation.
3.Post genital appendages: The cerci -These are the appendages of segment XI. They are found in Apterygota, all Hemibnetabola except Hemiptera & are also reported in Mecoptera & symphyta (Hymenoptera) from Holomentabola.
The cerci are simple in Orthoptera, annulated in Dicttyoptera & filamentous in Thysanura, Emphemeroptera & plecoptera. In some insects they represent sexual demorpheism.
They are primary tactile sense organs & are provided with the trichoid hair that may function as sound receiver or defensive devices (Darmaptera) or clasping organs(Embiptera) feeding organs (reptorial) as in Japygidae or many modify into lateral gills performing respiration and
ionic exchange (Zygoptera) or swimming organs (Emphemeroptera nymphs).
4) Secondary copulatory apparatus in Odonata: In male dragonflies the external genitalia & almost rudimentary. The funtnl genitalia the 2dry copulatory apparatus is developed as the ventral surface of 2nd & 3rd abdominal appendages.