Introduction to pinning insects

Author: Ryan Hill

Overview: In this lesson students are introduced to how to properly pin insects by reviewing insect morphology, insect orders and recognizing that the second and third thoracic segments contain large locomotory muscles that bind to the pin.

Lesson Concepts:

  • Insects can be grouped into orders based on their morphology (review).

  • Insects have body regions specialized for different functions.

  • Insects of different orders are taken care of (curated) in different ways.

  • Hard-bodied insects are best preserved by pinning.

  • Insects are pinned through the thorax.

  • Forewings cover thorax in some insect orders requiring care to ensure that pin goes through thorax.

California Science Education Standards:

  • Students should be able to communicate the steps and results from an investigation in written reports and oral presentations.

  • Bones and muscles work together to provide a structural framework for movement.

  • The slope of the linear graph as the constant in the relationship y = kx and apply this principle in interpreting graphs constructed from data.

  • Students should be able to construct appropriate graphs from data and develop quantitative statements about the relationships between variables.

  • Students should be able to formulate explanations by using logic and evidence.

  • Students should be ablte to analyze situations and solve problems that require combining and applying concepts from more than one area of science.

Grade span: 6-8 or 9-12

Materials:

  • Piece of blank paper and pencil for each student

  • Worksheet to be completed by students (attached)

  • Specimens to demonstrate correct and incorrect pinning

  • Specimens to illustrate different ways to prepare specimens of different orders for museum

Advanced preparation:

Photocopy worksheets, review morphology and insect orders.

Time: 50 minutes

Grouping: Not necessary, but can be done in groups of 3-5, especially if specimens are limited

Teacher background:

Insects are Arthropods with six legs, external mouthparts and many with wings (a few basal orders have not evolved wings and some orders have members that have evolved to be wingless). The insect body is composed of three main regions (together the tagmata), the head, thorax and abdomen. The head is specialized for sensory function, thorax for locomotion and abdomen for circulation, digestion, excretion, reproduction. Soft-bodied insects (and other arthropods) are preserved in 70% ethanol, as are immature stages of insects. Very small hard-bodied specimens may be pointed or fitted with very small “minuten pins”. Odonata are most efficiently preserved dried in clear envelopes. Other hard-bodied adults (nymphs and larvae are preserved in alcohol) may be pinned through the second or third thoracic segments between the forewings with the pin right of center and perpendicular to the insect body axes (see Figure 36-9 & 36-10).

Teaching tips:

This lesson is best if placed in context of field work/collecting trip and curatorial steps to make museum specimens, and after introductory lesson(s) on insect morphology and lesson(s) on identification of insect orders. After this introduction, students should practice pinning specimens soon to reinforce the concepts.

Vocabuary:

morphology, locomotion, head, thorax, abdomen, dorsal, lateral, curation
Advanced: prothorax, mesothorax, metathorax, tagmata

Procedure:

  1. Start with review by asking what is morphology and what makes an insect (3 pair jointed legs; three major body regions (each is a tagma): head, thorax, abdomen; external mouthparts; wings on some).

  2. Have them each fold piece of paper in row along short axis and then in each half draw an insect body on their paper with head, thorax and abdomen following a drawing you do on the board with insect head facing left and paper oriented tall and narrow (see attached example).

  3. Ask what is lateral/side view and dorsal/top view, and with paper lying tall and narrow in front of them have them label above top drawing “side view/lateral” and above bottom drawing “top view/dorsal”.

  4. Next review by asking what is contained in the different body regions [they have already been introduced to terms antenna, head, thorax, abdomen, legs, wings and recognize that these structures look different in different insect orders and the idea that differences in these structures can be used to identify order].

    • a.) Where are the legs attached? (thorax) Wings? (thorax) Are all legs on one segment? (no, there are three thoracic segments) Wings are on what segments? (second-mesothorax, and third-metathorax) On lateral view, have them draw legs and wings emphasizing different segments of thorax. Therefore what is function of thorax? (locomotion) In order to move what kind of tissue is inside thorax? (muscle)

    • b.) What is contained in head? (antennae, mouthparts) Therefore what is specialization of head? (sensory/feeding) On lateral view, have them draw lateral view of antennae, eyes and mouth for sensory and eating.

    • c.) Abdomen? (has visible posterior appendages, and hidden internal morphology) Specialization of abdomen? (digestion, reproduction) Label lateral view abdomen as containing digestive track inside and having reproductive organs.

  5. Next draw the antennae and legs sticking out in the top view on the bottom half of their paper. Ask them to think about how the view of the insect changes when they look from side compared with top: what can they see and not see so far? Later you’ll have them cover the thorax with the forewings.

  6. Ask what ways they can think of to preserve insects for study in museum. What issues are important?(avoid pests, sunlight, damaging specimens, ease of study) Can all insects be preserved the same way? Discuss curating insect specimens and different ways to do this that we’ll show them (pass examples around of Odonata envelopes, pinned Lepidoptera, Coleoptera, Orthoptera, pointed specimens, other orders in alcohol).

  7. What kind of insects should be pinned (hard-bodied ones, adults, NOT nymphs/larvae). Ask where would be best body part to place a pin to make a museum specimen that could last hundreds of years (Thorax b/c of thick cuticle of thorax and muscles for flight and walking will grip pin).

  8. So insects are pinned through the thorax so the muscles grip the pin AND they are pinned off to one side (just right of center) - write this on board for emphasis. Why do you think this is so? (so that no features along the midline are obscured, and to keep one side undamaged for study).

  9. Have them draw single pair of wings on the top view/dorsal view of their body (draw on board with them and tell them there are also halteres (thin clubbed hindwing in Diptera, a balance organ), where do they go? What segments of the thorax have the wings?(second and third) What order would this represent? Mark an “X” where you would pin this insect.
    (9i-9ii Extra drawing and Order review if time allows)

    • 9i. Have them add a pair of hindwings and tell them that there is a thin waist and stinger- what order is it? Where would you pin it?

    • 9ii. Have them expand the wing (lead them by drawing this on board) making previous wing the veins in a lepidopteran wing, add in more veins-tell them there are scales and coiled proboscis(tongue) and ask what order it is and where to pin it?

  10. Ask in what orders of insects could you put a pin directly through the thorax? Hymenoptera, Diptera, Lepidoptera, etc. Show them specimens of properly and improperly pinned specimens focusing them on pinning position.

  11. Ask them to think about a beetle and what makes a beetle a beetle (forewing=elytra that cover the hindwings and abdomen in most families). Can they see the thorax? (not really) What do they see when looking at dorsal view of beetle?(the forewings=elytra) Where are the forewings and wing bases? Where would they pin it? (through the forewing so that goes through 2nd/3rd thoracic segment)

  12. Revisit lateral view drawing of insect morphology and have them draw a beetle forewing lying over the back to illustrate that wing can lie over thorax. Show insect specimens illustrating this.

Reflection:

  1. In what other orders is it difficult to see the thorax in dorsal view, i.e. where you put the pin?(Orthoptera, Hemiptera)

  2. Review questions: what types of insects are pinned? Where are they pinned? What is a problem to watch out for?(forewing covering thorax)

  3. Give them worksheet with insect drawings (see attached) where they circle the thorax where wings articulate and place X on proper pin placement and label insect orders.

  4. Could also give them insects to pin if the lesson is done after a field trip and if time allows.

 
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