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Section 1a: Identification of Monarch Eggs and Larvae

Monarch Egg Close Up

This is the second video of the Monarch Larva Monitoring Project video training series, reviewing monarch biology and identification skills for eggs and larval instars.

Next Video in Training Series > Section 1b: Identification of Monarch Pupae, Adults, Host Plants, and Nectar Plants

Glossary of Terms

  • androconial scales
    an-dro-KO-nee-al): wing or body scales that disperse a pheromone.
  • Asclepias syriaca
    (u-SKLEE-pee-us sir-I-uh-kuh): common milkweed. The most common host plant for monarch larvae in the upper Midwestern U.S. Monarchs also eat other members of the genus Asclepias.
  • camouflage
    to hide or disguise. There are two types of camouflage: protective resemblance and protective coloration. Protective resemblance is when something looks like something else in its environment. Protective coloration is when something has the same color or pattern as its surroundings.
  • chorion
    KOR-ee-ahn): the hard outer shell of insect eggs. (In general, the chorion is the outermost membrane enclosing the developing embryo. In reptiles, this layer lies just inside the shell, and in mammals the chorion becomes the placenta.)
  • cuticle
    the hard outside part of the butterfly's skin that is no longer living.
  • eclose
    to emerge as an adult from the pupa stage.
  • family
    a category of classification that contains related genera.
  • genus (plural, genera)
    a category in a classification that contains one to many similar or related species.
  • hemolymph
    (HEE-muh-lim(p)f): the name for the blood of insects.
  • instar
    a period between larval molts. There are five of these periods in the growth of a monarch larva.
  • larva
    (LAR-vuh), plural, larvae (LAR-vee): the second stage, after the egg, in metamorphosis. Also known as a caterpillar. Monarchs molt five times in their larval stage, which lasts about 9-14 days.
  • Lepidoptera
    (lep-uh-DOP-ter-uh): the order of insects that is made up of butterflies and moths. This word should be capitalized, but the adjective lepidopteran should not.
  • meconium
    (mi-KO-nee-um): the fluid monarchs excrete shortly after they emerge from the chrysalis.
  • metamorphosis
    (met-uh-MOR-fuh-sis): the series of developmental stages through which insects go to become adults. Through metamorphosis a butterfly is transformed from an egg, to a larva, to a pupa, to a butterfly. There are two types of metamorphosis: incomplete (simple) and complete (complex) metamorphosis. The four distinct stages of metamorphosis found in butterflies is considered complete metamorphosis. Incomplete metamorphosis does not have a prolonged immobile (pupa) stage.
  • molt
    the process of shedding the skin or exoskeleton. Monarch larvae molt five times.
  • order
    a category in classification that contains related families.
  • pheromones
    (FAIR-uh-mohns): special chemicals released by some animals to communicate with other members of their species. They may be sensed over long distances to help mates find each other. They may also help ensure that mating only occurs with other members of the same species.
  • pigmentation
    coloration caused by all light wavelengths, but that of the color emitted, being absorbed.
  • proboscis
    (pro-BAHS-kiss): the adult monarch's feeding tube, for sucking nectar, which is coiled under the head when not in use.
  • prolegs
    the "false" legs on the abdominal segments of the monarch larva.
  • pupa
    (PU-puh) plural, pupae (PU-pee): the third stage in metamorphosis, after the larval stage. In monarchs this stage lasts 8-13 days.
  • pupate
    to change from a larva (caterpillar) to a pupa (chrysalis).
  • scales
    overlapping pieces of chitin (the same material of which exoskeletons are made) that insulate butterflies' bodies and wings, improve their aerodynamics, and give them color and markings. Many people think the scales look like fine dust on butterfly wings.
  • species
    a group of organisms recognized as distinct from other groups. Differentiates between members of a genus.
  • tactile setae
    TAK-tile SEE-tay): hairs through which butterflies and moths sense touch. They extend through the exoskeleton and connect to nerve cells inside the insect's body.
  • tentacles
    the fleshy black extensions at the front and rear of the monarch larvae, which function as sense organs. Also called filaments.
  • thorax
    the middle section of an insect's body. The wings (if present) and legs are attached to this segment.
  • true legs
    jointed appendages located on the thoracic segment of the larva. Contrast with prolegs.

Photo Credits (in order of appearance)

1. Monarch egg close-up: Monarch Lab Photo
2. 5th instar eating: Denny Brooks
3. Pupa on a leaf:
4, Adult male monarch on purple flower: Dave Astin
5. Common milkweed: Wendy Caldwell
6. Finding an egg on milkweed: Wendy Caldwell
7. Eggs on young milkweed: Gail Gilliland
8. Monarch egg close-up: Monarch Lab Photo
9. Hatching larva close-up: Siah St. Clair
10. Five larvae stages: Karen Oberhauser
11. Molting larva: Jessica Womack
12. 5th instar eating milkweed flower: Denny Brooks
13. 1st instar eating chorion:
14. 1st instar eating patterns: Karen Oberhauser
15. 2nd instar larva against ruler: Karen Oberhauser
16. Two 2nd instars: Karen Oberhauser
17. 2nd and 3rd instar comparison: Karen Oberhauser
18. Tentacles of 3rd instar close-up: Karen Oberhauser
19. True-legs: Karen Oberhauser
20. Pro-legs: Karen Oberhauser
21. 4th instar larva: Karen Oberhauser
22. 5th instar on milkweed: Wendy Caldwell
23. 5th instar eating: Denny Brooks
24. 5th instar eating pattern: Lynda Andrews Wayne
25. 2nd instar comparison: Karen Oberhauser
26. Recently molted 3rd instar: Karen Oberhauser
27. 3rd and 4th instar comparison: Karen Oberhauser
28. 5th instar size comparison: Kip Kiphart
29. Monarch egg look-alikes: Anurag Agrawal