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ACE Prep · Module 1 of 11

Insect Biology & Morphology

Quick answerUpdated September 24, 2026

What does ACE module 1 cover?

This module covers arthropod classification, insect anatomy, development, and the 12 pest management orders. Understanding how insects are built and how they develop is the foundation for understanding how pesticides work and why control strategies differ by pest.

Key factApproximate exam weight: 10%.

Reviewed by LTK editorial team

Must-know facts

  • Arthropods have a hard exoskeleton, segmented bodies, and jointed legs. The four pest management classes: Insecta (6 legs), Arachnida (8 legs/2 body regions), Chilopoda (centipedes), and Diplopoda (millipedes).
  • Insect body regions: head (sensory — antennae, eyes, palpi), thorax (movement — 3 pairs legs, 2 pairs wings), abdomen (digestion, reproduction).
  • Leg segments in order: coxa → trochanter → femur → tibia → tarsus.
  • Exoskeleton is made of chitin. Desiccant insecticides (diatomaceous earth, silica aerogel) disrupt the waxy cuticle layer.
  • Insects breathe through spiracles and tracheae. Oils kill small insects by clogging spiracles (physical mode of action).
  • Gradual (incomplete) metamorphosis: 3 stages — egg, nymph, adult. Examples: cockroaches, termites, grasshoppers. Nymphs resemble adults.
  • Complete metamorphosis: 4 stages — egg, larva, pupa, adult. Examples: flies, beetles, butterflies, fleas, ants, bees.
  • The orders that matter most in pest work: Collembola (springtails, now usually grouped with other hexapods outside the true insects), Zygentoma (silverfish, formerly Thysanura), Orthoptera (crickets/grasshoppers), Blattodea (cockroaches and termites; termites were formerly the order Isoptera), Dermaptera (earwigs), Hemiptera (true bugs), Coleoptera (beetles), Siphonaptera (fleas), Diptera (flies), Lepidoptera (moths/butterflies), Hymenoptera (ants/bees/wasps).
  • Mouthpart types: chewing (beetles, caterpillars, termites), piercing/sucking (fleas, lice, true bugs), sponging (house fly), siphoning (moths/butterflies).
  • Scientific naming: Genus species. Example: Blatella germanica. Common names vary by region; scientific names are universal.

What the exam likes to ask

  • If asked about a pesticide's mode of action affecting the cuticle, think desiccants (DE, silica aerogel).
  • If asked how oils kill insects, the answer is physical suffocation via spiracle clogging.
  • If asked about metamorphosis type for a specific pest, know: cockroaches/termites = gradual; flies/beetles/fleas/ants = complete.
  • An insect with piercing-sucking mouthparts cannot cause chewing damage — know the mouthpart types and what damage they cause.

Field takeaways

  • Knowing insect orders helps you make sense of behavior, life stage, and vulnerability windows.
  • Metamorphosis type tells you which life stages to target with IGRs vs. adulticides.
  • Mouthpart type helps diagnose plant or structural damage even before you see the pest.

Listen, watch, read

Podcast

The Alien Engineering of Insect Anatomy

Deep dive into insect morphology — body segments, appendages, mouthparts, and why anatomy drives pest behavior.

Slide deck · 15 slides

ACE Insect Biology

View the slides

Insect Biology & Morphology

10:00

Insect Detective Lineup

8:28

Module 1 quiz

25 questions. Answer them all, then grade to see the reasoning.

  1. Q1How many pairs of legs does an adult insect have?
  2. Q2Which type of metamorphosis is correct for fleas?
  3. Q3Diatomaceous earth kills insects primarily by
  4. Q4Which insect order contains cockroaches?
  5. Q5An insect with piercing-sucking mouthparts is found on a plant with chewed leaf margins. Which statement is most accurate?
  6. Q6Chitin, the main structural material of the insect procuticle, is chemically best described as a
  7. Q7On a winged adult insect, which thoracic segments carry the wings?
  8. Q8Which leg segment joins the insect leg to the body?
  9. Q9Air enters an insect's body mainly through
  10. Q10A horticultural oil spray kills soft scales and aphids mainly by
  11. Q11The empty, insect-shaped skin left behind after a molt is called the
  12. Q12A technician finds a pure white cockroach among normal brown German cockroaches. The most likely explanation is that it is
  13. Q13Which of these pests develops by gradual (simple) metamorphosis?
  14. Q14An immature insect with visible wing pads on its thorax is most likely a
  15. Q15In complete metamorphosis, larval tissues are broken down and rebuilt into the adult body during the
  16. Q16A coiled, straw-like proboscis used to sip nectar is the mouthpart type of
  17. Q17Which fly has sponging mouthparts that cannot pierce skin?
  18. Q18In the scientific name Supella longipalpa, the word Supella is the
  19. Q19Why can only female bees, wasps and ants sting?
  20. Q20An arthropod has two body regions, four pairs of legs and no antennae. It belongs to the class
  21. Q21A long, cylindrical arthropod with two pairs of legs on most body segments is a
  22. Q22An insect has hardened front wings that meet in a straight line down the back and protect membranous hind wings. Its order is
  23. Q23An insect has a jointed beak for piercing and sucking, and front wings that are thick near the base and membranous at the tips, folded flat over the back. Which order is it?
  24. Q24Based on molecular evidence, most entomologists now classify termites as
  25. Q25Desiccant dusts such as silica aerogel will give the best results in which location?

0 of 25 answered

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