Parasa lepida, the Blue-streaked Nettle Grub: 7. Eclosion

Earlier posts: 1; 2; 3; 4; 5; and 6.

Pupation of the the Blue-streaked nettle grub (Parasa lepida) takes place within a hard, nut-like oval cocoon, 7-9×10-16mm loosely covered with silk and larval bristles. Under controlled conditions where the larvae were unable to move to the ground by a water barrier, the cocoons were attached to the twig or the underside of a leaf (below).

However, I did find a cocoon in my garden attached to a leaflet of the Lipstick Palm (Cyrtostachys renda). According to this LINK they are found buried in the soil or among leaf litter.

The top of the cocoon comes off as a lid at the time of eclosion to allow the adult to crawl out (above). This takes place 20-23 days after formation.

As the newly eclosed moth crawls out of the pupal case, it hangs on to the cocoon shell and injects fluids from the abdomen to inflate the limp wings. Just before flying off it ejects a jet black excess fluid, known as meconium, a metabolic waste left over after metamorphosis.

Tried as I did, even leaving the video cam on the entire night, and even the following night, I failed to catch the magical moment.

In one case I did notice the moth after it emerged in the early morning. But in trying to move the twig with the cocoon for a better location, the moth fell from the top of the cocoon onto the table top, leaving a trail of black liquid – see video below.

The moth was rescued – see the three images above. It eventually flew off.

YC Wee
Singapore
22nd November 2016