Ethanol Fixation
Definition
Preservation of killed insect specimens in 70-80% ethanol. The alcohol denatures proteins and prevents decay, maintaining morphological structure for months to years.
- Concentration used
- 70-80% ethanol
- Mechanism
- Protein denaturation preventing decay
- Applies to
- Killed insect specimens in forensic entomology
- Preservation duration
- Months to years
Common questions
Why is 70-80% ethanol used rather than a higher concentration?+
That range denatures proteins effectively while limiting excessive tissue shrinkage and brittleness that stronger concentrations can cause, keeping morphological features intact for later species identification.
Does ethanol fixation preserve DNA as well as morphology?+
Ethanol preservation is primarily chosen for morphological integrity; DNA can degrade over long storage, so specimens intended for molecular identification are often preserved separately or processed for DNA extraction sooner rather than relying on long-term ethanol storage alone.
Are all insect life stages preserved the same way in ethanol?+
No. Larvae are commonly killed first, often in hot water, before transfer to ethanol to prevent discoloration and distortion, while adults may be preserved directly, so the killing step before fixation matters for accurate identification.
Related terms
- Chain of Custody
- The documented chronological record of who collected, handled, transferred, and examined a piece of evidence. For digital evidence, chain of custody includes...
- Hot-Water Killing
- The method of killing insect larvae by immersion in water at approximately 75-85 degrees C for 30-60 seconds before fixing in ethanol....
- Instar Determination
- Assigning a collected larva to first, second, or third instar based on body length, spiracle morphology, and mouthhook features. Instar determines which...
- Scene-to-Laboratory Transfer Record
- The portion of the chain of custody covering the movement of samples from the scene or mortuary to the receiving laboratory, including...
- Voucher Specimen
- A preserved specimen formally deposited in a collection or retained in the case file as a permanent reference. In forensic entomology, the...