Factors Influencing Insect Abundance

Factors Influencing Insect Abundance

• Factors influencing population growth can be categorized as biotic (density-dependent) or abiotic (density-independent).
• Biotic factors include interactions between individuals of the same species (intraspecific) or different species (interspecific). These interactions can be beneficial, harmful, or neutral.

Interaction Between Organisms

• Competition: Members of a species or different species compete for limited resources (food, mates, oviposition/pupation sites). Competition is more intense when populations increase and resources are limited.

• Intraspecific Competition: Competition among individuals of the same species for resources includes aggregation, concurrence, cannibalism, sexual interactions, parental care, and social life.

• Aggregation: Insects tend to concentrate in larger numbers than their normal distribution. This can alter the microclimate and affect morphology, physiology, and ecology.

• Concurrence: Many insects are solitary, but some gather for activities like hibernating, feeding, or mating. Overcrowding can lead to competition for resources and may be harmful to the species.

• Cannibalism: Overcrowding and food scarcity can lead to cannibalism—individuals of the same species killing and consuming each other.

• Association of Sexes: The sex ratio affects population growth. Different sex ratios can lead to different numbers of offspring produced.

• Parental Care: Many insects care for their eggs and young by protecting them from predators, providing food, or cleaning them.

• Social Life: Some insects (honeybees, termites, ants, wasps) exhibit social behavior—complex interactions and division of labor for the welfare of the colony.

Interspecific Competition

• Competition between members of different species occurs when they have the same resource requirements. Species with identical requirements cannot coexist in the same place long-term. Example: Flour beetles (Tribolium castaneum and Tribolium confusum).

Positive Interactions

• Symbiosis (Symbiont): Both insects and their host live together without negative effects.

• Commensalism: One insect benefits without harming the host. Examples: Staphylinid beetles living in Hymenoptera nests to consume leftover food.

• Phoresy: A commensal using its host for transport instead of food. Examples: Parasitoid wasps using moths for transport.

Mutualism

• When both interacting species benefit from the relationship. Example: Ants and aphids, providing shelter and food respectively.

Negative Interactions (Predators and Parasites)

• Predators: Free-living insects that hunt and consume other animals (prey). Obligate predators prey on one species, while facultative predators prey on multiple species.
• Required prey for predator growth: Some have specific requirements for numbers/types of prey.

Parasites

• An organism that depends on another (host) for metabolic support. This often involves weakening or killing the host.
• Super Parasitism: One host is attacked by numerous individuals of the same parasite species.
• Multiple Parasitism: One host is attacked by multiple species of parasites.
• Hyperparasitism: A parasite is itself attacked by another parasite.

Food

• Insects directly or indirectly rely on plants for food.
• Factor influencing insect abundance.
• Food quantity affects survival, longevity, reproduction, and distribution of insects.
• Food quality (nutritional status of plants/food source) also impacts insect populations.

Quantity and Quality of Food

• Quantity: Short supply contributes to intraspecific and interspecific competition.
• Quality: Nutritional availability from different plants/food sources impacting insects differently. Insect's cannot produce their own food.