Types of Reproduction in Insects
Physiology of Reproduction
Types of Reproduction
- Majority of female insects are oviparous that is, they lay eggs.
- Embryonic development occurs after oviposition by utilizing the yolk, e.g. Head louse moths.
- Unlike oviparous, here initiation of egg development take place within the mother.
- The life cycle is shortened by retention of eggs and even developing young within the mother.
- Four main types of viviparity are observed in different insect groups.
- Fertilized eggs containing yolk are incubated inside the reproductive tract of the female and hatching of egg occur just prior to or soon after oviposition e.g. Thysanoptera, some cockroaches, few beetles, and some flies-(fleshfly).
- Fecundity of this group is low.
ii. PESEUDOPLACENTAL VIVIPARITY
- This occurs when a yolk-deficient egg develops in the genital tract of the female.
- The mother provides a special placenta-like tissue, through which nutrients are transferred to developing embryos.
- There is no oral feeding and larvae are laid upon hatching. e.g. aphids, some earwigs, psocids and polytenid bugs.
iii. HAEMOCOELOUS VIVIPARITY
- This involves embryos developing free in the female’s haemolymph with nutrients taken up by osmosis.
- This form of internal parasitism occurs only in sterpsiptera and some gall midges.
iv. ADENOTROPHIC VIVIPARITY
- This occurs when a poorly developed larva hatches and feeds orally from accessory (milk) gland secretion within the uterus of the mother’s reproductive system.
- The full grown larva is deposited and pupariates immediately (eg) tsetse flies, louse or wallaby flies, bat flies.
- Reproduction without fertilization is called parthenogenesis.
Different types of parthenogenesis are as follows
I. BASED ON OCCURRENCE
i. Facultative (not compulsory) – e.g. bee.
ii. Obligatory or constant (compulsory) – e.g. stick insect
iii. Cyclic or spordic : alternation of gamic and agamic population, e.g. aphid.
II. BASED ON SEX PRODUCED
i. Arrhenotoky: Produce male e.g. bee
ii. Thelytoky: produce female e.g. aphids
iii. Amphitoky or deuterotoky: produce both male and female e.g. cynipid wasp.
III. BASED ON MEIOSIS
i. Apodictic : no meiosis occurs
ii. Automictic: meiosis occurs, but diploidy is maintained
- This form of asexual reproduction involves the production of two or more embryos from one egg by subdivision.
- Mostly observed in parasitic insects (e.g. platygaster).
- Nutrition for a large number of developing embryo cannot be supplied by the original egg and is acquired from the host’s haemolmph through a specialized enveloping membrane called trophamnion.
- Some insect cut short their life cycles by loss of adult and pupal stages.
- In this precocious stage gonads develop and give birth to young one by parthenogenesis.
i. Larval paedogenesis – e.g. gall midges
ii. Pupal paedogenesis – eg Miaster sp.