Entomology: Insects and Their Benefits

Study Notes

Insects are predators that help maintain the balance of the environment by consuming harmful insects.
Parasitoids live on or in their host, eventually killing it.
Insects provide multiple benefits to humans, such as honey, beeswax, silk, shellac, and dyes.

Apiculture is the rearing of honeybees (Apis mellifera) for honey, wax, royal jelly, and other products.
Sericulture is the rearing of silkworms (Bombyx mori) for the production of silk, often raised on mulberry trees (Morus alba).

Insects have three distinct body regions: head, thorax, and abdomen.
Insects have one pair of antennae.
Insects have three pairs of legs, although some are legless or have additional leg-like appendages in their larval stage.
Insects often have one or two pairs of wings, attached to the second and/or third thoracic segments.
Insects have postoral appendages on their head, including mandibles, maxillae, labrum, and labium.

The insect body wall consists of an epidermal cell layer, a cuticle, and a basement membrane.
The epidermal cell secretes molting fluid important for growth.
The cuticle is a non-cellular layer that covers the entire body surface and lines internal structures.
The epicuticle is the outermost thin layer, containing cuticulin, wax, and cement.
The exocuticle is the middle layer, providing strength and resilience, composed of chitin.
The basement membrane separates the body wall from internal organs.

The head is the anterior body segment, housing the eyes, antennae, and mouthparts.
Insects can be classified by head position in relation to the body axis.

Hypognathous: Mouthparts at a right angle to the body axis (e.g., grasshoppers, roaches, mantids).
Opisthognathous: Mouthparts projecting backward between the legs (e.g., cicadas, bugs, leafhoppers).
Prognathous: Mouthparts in line with the body axis (e.g., termites, ground beetles).

Insect mouthparts vary in type based on dietary needs.
Mandibles: Tooth-like structures used for chewing, grinding, tearing, or pinching.
Maxillae: Segmented structures used for mastication, located behind the mandibles.
Labrum: Movable, flap-like structure acting as the "upper lip."
Labium: Structure found posterior to maxillae, acting as the "lower lip."
Hypopharynx: Tongue-like structure hanging from the head's floor, bearing the opening of salivary ducts.

Mandibulate or Chewing: Mandibles cut and grind solid food, maxillae and labium push food into the esophagus.
Cutting-Sponging: Modified mandibles act as blades, maxillae form long probing styles.
Sponging: Non-functional mandibles and maxillae, forming a proboscis with a sponge-like apex called labella.
Chewing-Lapping: Mandibles and labrum for chewing, used for grasping prey, molding wax, or nest materials.
Piercing-Sucking: Modified mouthparts pierce tissues and suck juices.
Siphoning: Long proboscis formed from maxillae, used for sucking nectar or liquids.
Rasping-Sucking: Cone-shaped beak formed from clypeus, labrum, parts of maxillae, and labium.

Antennae are elongated, segmented structures used for sensory functions and, sometimes, defense.
Three main parts:
- Scape: Basal segment
- Pedicel: Second segment
- Flagellum: Whip-like part beyond the pedicel