Reproduction in insects

It provides a brief knowledge about Reproduction in insects. Also helps in differentiation of male and female reproductive systems.

1. S yed M uhammad A li Z ahid Department of Entomology University College of Agriculture University of Sargodha

2. Insect Physiology, Ent-502, 3(2-1) Reproduction in Insects by: Syed M. Ali Zahid (BAGF13-E270)

3. What is Reproduction ? A biological process by which new individual organisms (off-springs) are produced from their parents OR Sexual or asexual process by which organisms generate new individuals of the same kind A fundamental feature of all known life

4. Types of Reproduction in Insects Insects have different & opposite sexes and reproduce by sexual reproduction There are following 7 types of reproduction in insects Oviparity Viviparity Parthenogenesis Paedogenesis Polyembryony Hermaphroditism Castration

5. Oviparity Most common mode of reproduction in insects Insects lay the fertilized eggs, which hatch outside the body of the female Such insects are said to be oviparous E.g. Butterflies, Moths, Flies, Beetles, Bugs, Locusts, Grasshoppers, Dragonflies, Mayflies, Springtails, Bristletails etc.

6. 2. Viviparity Eggs complete their embryonic development & hatch within the body of the female Hence the female gives birth to the young ones, instead of laying eggs Such insects are said to be viviparous E.g. Aphids, certain flies, Stylopids etc.

7. 3. Parthenogenesis Eggs undergo full development without having been fertilized Females lay the unfertilized eggs Eggs have both the haploid (half) or diploid (double) number of chromosomes These eggs undergo full development & give rise to males, females or both sexes. E.g. Aphids, Bees, Wasps, Some whiteflies, Thrips etc.

8. 4. Paedogenesis Immature stages (larvae & pupae) produce young ones Have functional ovaries in which eggs are developed parthenogenetically E.g. In some cecidomyids ( Miastor & Oligarces ) the larvae gives birth to other larvae, which become adult under favorable conditions In certain midges ( Henria & Tanytarsus ) the pupa produces larvae, some of which become normal adults A few beetles ( Micromalthus ) also show this phenomenon

9. 5. Polyembryony It is a rare phenomenon A single egg produces two or more larvae E.g. several parasitic wasps (Hymenoptera), some cecidomyids & a few Stylopids

10. 6. Hermaphroditism It is an extremely rare phenomenon A single individual has both the male & female reproductive organs E.g. In the scale insect ( Icerya purchasi ) the outer cells of the gonads produce eggs, while the inner cells produce sperms Thus the eggs are fertilized in the gonads by sperms in the same individual In the Phorid flies of the genus Termitostroma each individual has a pair of ovaries & testis to release the eggs & sperms

11. 7. Castration Production of mature gametes is ceased in the organism having well developed gonads This may occur in any insect Due to any disease attack, any parasitic attack or physiological disturbance

12. SEXUAL ORGANS IN THE MALE & FEMALE INSECTS Male Reproductive organs Paired testis composed of follicles (testicular tubes) Paired vasa deferentia Vesiculae seminales Median ejaculatory duct Accessory glands a. Mesadenia b. Ectadenia 6. ---------- 7. Genitalia Female Reproductive organs Paired ovaries composed of ovarioles (ovarian tubes) Paired oviducts Egg-calyces Common oviduct & vagina Accessory gland a. ------- b. Colleterial glands 6. Spermatheca 7. Bursa copulatrix 8. Ovipositor

13. Male Reproductive organ Female Reproductive organ

14. REPRODUCTIVE SYSTEM Male Reproductive system: Consists of a pair of testes Each testis is composed of a large number of tubular testicular follicles Each follicle opens by means of a short, slender duct, the vas efferens (pl. vasa efferentia), into the long genital duct, the vas deferens (pl. vasa deferentia).

15. Follicles are attached to the body wall by a suspensory ligament Vasa deferentia opens into a wider tube, the ejaculatory duct Anterior to the points of opening of vasa deferentia, two groups of long tubular accessory glands also open into the ejaculatory duct A medial pair of accessory glands serve as seminal vesicles for storing the sperms The ejaculatory duct opens into ejaculatory sac , which opens into the aedeagus

16. Female Reproductive system:

17. Female Reproductive system: Consists of a pair of ovaries Each ovary is composed of a large number of tubular ovarioles which arise from the side of the oviduct. Ovarioles are attached to the body wall by suspensory ligament The oviducts also extend anteriorly to form two accessory glands .

18. Oviduct makes a short bend and unite in the common oviduct (vagina) The vagina terminates in the genital chamber . Spermatheca is a sac-like oval body which receives and stores the sperms It opens by means of a coiled spermathecal duct into the genital chamber Ovipositor is present at the end of female reproductive system

19. Female Reproductive system: