Insect Curation
Part of the Biodiversity in the Schoolyard (BitS) unit
Authors: Ryan Hill, Nicole VanderSal, and Alison Purcell
Overview: In this lesson, students will learn how to curate insects that they collected in previous lessons.
Lesson Concepts:
Specimen curation is a way to preserve field collected specimens to catalogue what species exist in a certain area or to have reference specimens to compare to others in the future.
Arthropod specimens must be properly taken care of so that they are not damaged and may be easily studied.
Insects and non-insect arthropods are preserved in different ways according to how soft the body is.
All specimens must have a data label providing the location, date, and collector.
Soft-bodied arthropods change shape if dried and so are best preserved and studied in fluid (70% ethanol).
Insects with a hard exoskeleton do not change form when dried and so are preserved on insect pins.
Grade Span: 9–12
Materials:
Insects pins (size #2 or 3)
Pinning foam, flat packing foam in approximately 5" x 5" squares (at least 1 per student) works well
Insect drawers or boxes
Note cards for making "abdomen supports"
Scissors
Advance Preparation:
Gather all required equipment and remove insects collected from freezer 1-3 hours before lesson.
Print small, pinning labels (~ 1 x 2 cm to be placed on pin under insect) with State, County, local site data, date, student's name, and sampling method. Must have enough for each student (~ 10).
Print small, fluid specimen labels (~ 1 x 4 cm, to place in vial with specimen(s)) with State, County, local site data, date, student's name, and sampling method. Must have enough for each student (~ 10). Note: Both label types should be printed on laser printers so that ink is fixed to paper (should be warm to touch after printing) and will not come off in ethanol.
Time: 1 hour
Grouping: Have students work in groups of 2 to 4.
Teacher Background: (optional)
Arthropods have a hard exoskeleton but some are still very "soft-bodied." Such soft bodied insects do not make good specimens if pinned. Because of this, soft bodied insect adults, all immature insects (nymphs/larvae), and non-insect arthropods (e.g., spiders, centipedes, scrorpions, etc.) are preserved in ethanol. Only adult insects that have a robust thorax are pinned. This is because only these have enough thorax exoskeleton and muscle to support the weight of the insect on the pin. In fact, the inside of the insect exoskeleton has many rod-like and ridge-like struts and invaginations where muscles attach.
Insects with complete metamorphosis have immature stages that are easily identified as such and are soft bodied (e.g., grubs, maggots, caterpillars). However, immatures of orders with incomplete metamorphisis look like miniature adults so require a bit more care. These immature insects do not have fully developed wings. Instead they have "wing buds" of increasing length (e.g., true bugs). If in doubt about whether an insect is adult or not, it is safest to preserve it in ethanol (it can always be pinned later).
Teaching Tips: (optional)
To help students remember the concept of pinning adult insects through the thorax, emphasize the thorax being the body region specialized for locomotion (walking, running, flying). Locomotion requires muscles and hard exoskeleton for support, both present in the thorax and required for pinning an insect.
Vocabulary: curate/curation, exoskeleton, thorax, head, abdomen
Procedure:
Introduction (10 minutes): Demonstrate the process of correctly pinning insects on the board.
Only adult insects are pinned. All soft-bodied adult insects, immature insects and non-insect arthropods are preserved in ethanol. Adult insects are pinned through the thorax in the 2nd and 3rd thoracic segments where wings and rear 2 legs attach. Pinning is always done the same way with pin perpendicular in lateral and head-on views, and placed right of the midline (show a diagram, or draw on board).
Procedure: grasp a specimen between thumb and forefinger in left hand (right if left-handed). Take pin in other hand and locate 2nd and 3rd thoracic segments (look at sides of insect as well as dorsum). Insert pin into dorsum of 2nd or 3rd thoracic segments penetrating the exoskeleton but not too deep. Line up the pin as you push the pin deeper into the insect. Feel for the ventral exoskeleton and line up the pin in side view and head on view and when perpendicular in both views, push the pin through until the pinhead is a "good gripping distance" from the insect dorsum. A "good gripping distance" is one that allows people to grip the insect pinhead without touching the insect, keep in mind others may have much larger fingers than your own.
Obtaining the correct height on the pin can also be done with a pinning block. Once the insect pin is completely through, forceps may be helpful in adjusting height on the pin. A useful trick is to use a card stock/note card rectangle ~ 1.5x2 to ~ 2x3 cm to support the insect abdomen and legs until they dry. Fold the card rectangle along its long axis making a "v", then take the insect on the pin and pin into the card bringing it up under the insect so that the "v" cradles the insect legs and abdomen (see diagram).
Then with another insect pin gently move the legs and antennae back, and abdomen to the center to make a nice presentation. Now the specimen should have a label placed under the card "v" and set on the foam to dry. After several days to a week air drying, the card should be removed and the label replaced and the insect is ready for further study.
Fluid preserved specimens can be placed, using soft-touch forceps, into a vial with ethanol and data label. Preserve each student’s fluid samples in a separate vial with appropriate label to sort and identify later. Students can sort similar looking specimens into separate vials if time and materials allow.
Curation (35 minutes): Hand out specimens with labels, pins, foam, and card supports. Tell students to pin as many of their insects as time allows. Remind students to label each insect as they go — the data must be correct! Walk around to students to help them individually.
Clean-up (5-10 minutes)
Place all insect specimens in a dry and warm area so they can dry out (oven or in warm part of room). It is best if specimens are not in the sun, but even this is okay if just for a few days.
