Collection Methods
The right collection method depends on the animal group being studied. Sweep nets are used to collect flying/crawling insects and other arthropods from vegetation. Pitfall traps — containers sunk flush with the ground, sometimes baited — collect ground-dwelling invertebrates that fall in and cannot climb out. Plankton nets (fine-mesh cone-shaped nets towed through water) collect small aquatic organisms. Hand-picking/forceps is used for slow-moving or sessile specimens like snails or sedentary insects. Kick-sampling in a stream (disturbing the substrate upstream of a held net) collects benthic invertebrates for freshwater surveys. Whatever the method, the key principle is to disturb the habitat as little as possible and record the exact locality, date, and habitat type at the time of collection — data that becomes worthless once separated from the specimen.
Killing Methods
Where specimens must be killed for study (rather than observed live and released), a killing jar/bottle containing a fumigant such as ethyl acetate is standard for insects — it kills quickly with minimal damage to delicate structures like wings and antennae, which alternatives (crushing, freezing slowly) would destroy.
Preservation: Wet vs Dry
Wet preservation immerses the specimen in a preservative fluid and is used for soft-bodied organisms (worms, molluscs, larvae, most vertebrates for dissection). Formalin (a dilute formaldehyde solution, typically around 4-10%) is a fixative — it cross-links proteins and halts decomposition and autolysis, and is normally used first for a short fixation period. Ethanol (typically 70%) is used for longer-term storage after fixation, since formalin causes brittleness and continued exposure damages tissue and DNA over time; ethanol also dehydrates and preserves without the same long-term structural damage.
Dry preservation is used for hard-bodied specimens whose structure survives without fluid — insects are pinned through the thorax on entomological pins and dried in a setting board (with grooves that spread the wings symmetrically before they stiffen); shells and exoskeletons are simply air-dried; vertebrate skins are taxidermied (mounted over an artificial form) or prepared as study skins (stuffed simply, limbs folded, for reference collections rather than display).
Labelling
Every preserved specimen needs a label recording, at minimum: species name (or best identification), collection locality, date, collector's name, and habitat notes. A specimen without accurate label data has essentially lost its scientific value, since it can no longer be linked to a place, time, or ecological context — this is emphasised constantly in zoological methodology because it is the single most common practical error.
Why This Matters for Your Exams
Exam questions often present a specimen type (e.g. "a soft-bodied marine worm" or "a butterfly") and ask you to justify a preservation method — always reason from the physical nature of the tissue (soft and easily decayed needs fluid preservation; hard exoskeleton can be dried) and from purpose (short-term fixation = formalin, long-term storage = ethanol). Also be ready to explain why labelling matters, not just that it is required.