Saturday, May 17, 2008

Katydid (Caedicia simplex)

On April 22nd a katydid nymph (Caedicia simplex) was spotted in a Correa lawrenciana (native fuschia) near the front door. Most insects have become inactive since the onset of cooler weather, so the cold-tolerant katydid has been the subject of close photographic scrutiny.

Unlike their terrestrial relatives, the grasshoppers, katydids spend most of their time in trees or shrubs. As they ingest material from their food plant their colours develop to match the plant on which they feed and rest.

The peregrinations of this particular katydid nymph are fairly limited. Some evenings it ventures 7 cm to the top of the Correa, but most of the time it stands, head downwards, on a leaf.

There was a moment of high excitement on May 3rd when it shed its exoskeleton! Nymphs (depending on the species) take weeks or months to reach full size and will shed their exoskeletons several times while they grow. Eventually wing buds, then wings, develop. I'm expecting that an adult, fully winged katydid will venture further than the Correa...

Male katydids ‘sing’ to attract females; they stridulate by rubbing together specialized veins on their wings. The vigour of their singing is dependent on temperature. To attain the necessary thoracic temperature for stridulation male katydids (most females are silent) shiver.

A 74mm katydid species that lives in the forests of North America, Neoconocephalus robustus, must get its flight muscles to 30 degrees before it can belt out its apparently ear piercing call. The females seem to prefer the loudest (and hottest) males.

Katydids "hear" with their tympanum, a small slit in their tibia (visible in the above picture) covered by a pressure-sensitive membrane.


Showchicken said...

well done mum!

Denis Wilson said...

I have been remiss in not browsing your "back catalogue" before. Beautiful photos.
Loved the Thismia photo. I knew the late Pat Jordan who discovered them in Australia (in Bundanoon). I am sure that someone in official position down there in Tassie would like your photo for reference purposes.
Stunning image of the Katydid moulting. It always feels special to witness such a moment. I once saw a colourful Huntsman Spider doing that. Had the photo on my screen saver for ages, till I decided it was too scarey. An upside-down Huntsman half as big as my screen. Your image is very pretty. Presumably the same Katydid as featured in your later stories.
Lovely work