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B. Understanding Cicadas (Continued)

6D. Dissections

Observing the detailed parts of the male abdomen may require careful separation of the parts and study under a dissecting microscope. Since cicadas are very bulky and tough (strongly sclerotized) insects, both dissection and storage of the parts after study is somewhat of a challenge.

Drawing of the abdomen (tibicen) of the male cicada. The terminal segment is withdrawn partially into the preceding segment and includes these parts: hypandrium, uncus, theca and vesica.

Anatomical drawing of the abdominal structures of the male cicada

Starting from fresh or alcohol-preserved specimens is preferable because the segments of the abdomen may be pried apart and any delicate membranes severed with a fine knife or even a sharp needle or insect pin. But if you have only an air-dry specimen, attempting to cut away part of the abdomen will probably shatter the cuticle. Applying some alcohol to the abdomen for a few minutes will remove most of the water-repellent waxes. Then, soaking the specimen in water for at least three hours should make the cuticle flexible enough for dissection.

The male terminal segment usually is withdrawn at least partially into the preceding segment. Lifting up the preceding plate (sternite 8) should allow you to insert a pin at the base of the lower part of the terminal segment (hypandrium) and lever it forward until its retaining membranes can be severed. If this fails, cut away the apical half of the abdomen entire, leaving the tymbals, tympana and associated opercula untouched. The dissected part of the abdomen should then be immersed in potassium hydroxide solution (one solid pellet of KOH in water in a spot plate concavity) and gently heated for 20-30 minutes until the fat and muscle tissue has mascerated.

Warning: KOH is highly reactive; it will rapidly begin to eat away at any skin or other tissue it touches. Spills should be flushed immediately with copious amounts of water.

Once maceration has begun, excess tissues and cuticle fragments may be discarded, leaving only the terminal segment. The remaining tissues adhering to this segment may be expelled by gentle pressure, and then the capsule should be thoroughly rinsed in water to remove the remaining KOH. The washed specimen can be blotted quickly on tissue or towel to remove excess water, and then transferred to a small dish with glycerin at least 5 mm deep to completely cover the specimen. Once it has been examined under a microscope, the specimen should be retained in glycerin in a small capsule and kept with the dry specimen from which it came. Since cicadas are large insects, a capsule for retaining dissected parts must be larger than a standard insect micro vial (6 mm external diameter, 3 mm internal). A cheap but suitable capsule is a 0.5 mL micro centrifuge tube with flat snap lid (7 mm inside diameter).

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