Reproductive strategies Flashcards
Sexual reproduction
- Most common form.
- Fertilization of eggs.
- Direct or indirect sperm transfer.
Indirect sperm transfer
type of sexual reproduction
Male deposits spermatophore & female takes it into genital opening
Mostly in primitive wingless insects and other Hexapoda
Methods of indirect sperm transfer
- Female may be directed to it by the male
- Spermatophore produced when insects are found in aggregation
- Spermatophore may be produced in large number
Direct sperm transfer
type of sexual reproduction
Aedeagus enters female & sperm is transferred directly
* Species-specific position
* Species-specific morphology
Asexual reproduction
Development from unfertilized eggs. Obligatory (no males) or facultative.
Haemocoelic insemination
Type of direct sperm transfer
Injection of sperm into body wall of female
Spermalege
Organ in bed bugs through which hemocoelic insemination occurs
Parthenogenesis
Type of asexual reproduction
- Most common type of asexual reproduction
- Only females are produced
- Eggs develop without being fertilized
XO sex determination system
Sex determination
- X = female
- XO = male
Haplodiploidy
Sex determination
Sex determined by # of chz. an insect receives (Hymenoptera)
* Unfertilized egg: male (haploid)
* Fertilized egg: female (diploid)
Viviparity
Embryonic development
- Give birth to live young
- Embryonic development is completed within the body of the female.
- Silverfish, some cockroaches, some flies, some beetles and in aphids
Oviparity
Embryonic development
- Production of eggs that hatch outside the body (most insects)
- Embryonic development starts outside the body
Swarming
Mate location and recognition
- Multiple individuals of the same species aggregate together
- The swarms usually consist of males, waiting for a female to pass by
- Swarms are the result of a common response to a visual marker
- Good when individuals are rare or dispersed
Flashing
- Fireflies
- Both sexes produce light.
- Females often flightless: respond to the flashing of the male.
- Duration and frequency of flash is species-specific
Singing
Mate location and recognition
- Usually only male.
- Stridulation: Rubbing together 2 body parts
- Vibration of special membranes (tymbals)
- Striking body part against substrate
Pheromones
Mate location and recognition
- Often produced by female
- Detected by male’s antennae
- Can detect very low levels of pheromone
- Great way of finding mate over a long distance
Courtship
Close-range attraction mechanism that induces sexual receptivity before mating
Visual displays
Courtship
- Usually performed by males
- Movement of body parts, display of color patterns, elaborate dance
Tactile stimulations
Courtship
- Occurs immediately before and sometimes during copulation.
- Involves rubbing of antennae, palps, legs, abdomen, etc.
- Important for final species recognition
Pheromones
Courtship
Used for close range recognition and sexual excitation
* Androconia: Scent scales on wings of male Lepidoptera
* Abdominal hairpencils: Found in male Lepidoptera and release pheromones
* In some species, males may clap their wings repeatedly catching the female’s antennae
Singing
Courtship
- Different sounds sometimes produced in close-range courtship
- Most singing insects continue once they found each others.
- Others sing only in close-up courtship
Nuptial gifts
Courtship
Males provide females with food item to increase chance of mating
Predatory insects
Nuptial gifts
Consist of a prey item
Ultimate nuptial sacrifice
Cannibalism of the male by the female
Non-predatory insects
Nuptial gifts
Consist of glandular product secreted by male
Spermatophylax
Sperm-free portion of spermatophore which is eaten by female
Copulation
Union of male and female genitalia, usually followed by insemination
Sexually selected adaptations in males to increase certainty of paternity
Copulation
- Male can displace sperm of other male
- Male can reduce effectiveness or occurrence of subsequent inseminations
Methods of displacing sperm
- Pushing sperm of other males to the back of spermatheca
- Direct scooping or indirectly by flushing out with sperm
Methods of reducing effectiveness
- Mating plugs
- Prolonged copulation
- Decreasing receptiveness of female to other males
- Improved structures for gripping female during copulation
- Guarding of females until oviposition
Hormones
Hormones and pheromones
Chemicals released by endocrine system & transported to specific sites where they influence a variety of physiological processes.
Ecdysone
Hormones
- Initiates molting process.
- Released by the prothoracic glands
Juvenile hormone
Hormones
- Inhibits metamorphosis.
- Released by Corpora allata
Pheromones
Hormones and pheromones
Chemicals released by exocrine glands to communicate with individuals of the same species.
Sex pheromones
- Long distance: Sex attractant. Produced by female to attract male
- Short distance: Courtship chemical. Produced by male prior to mating
Aggregation pheromones
Cause individuals of same species to aggregate
Spacing pheromones
Cause individuals to keep their distance from each other
Trail-marking pheromones
Communicate information on location of food source
Alarm pheromones
Signal danger causing insects to disperse or attack enemies
Social pheromones
Regulation of colony structure
