Tuesday, June 26, 2018

Leaf-foot Bug Birth

I was photographing an alien-looking bug when I noticed a small cluster of insect eggs on the underside of a leaf.  I stored them safely in a bug box, hoping to video their births.  

The creature was a common leaf-footed bug, characterized by the leaf-shaped tibias on the hind legs.  These are plant-sucking bugs, similar to stink bugs, commonly considered garden pests. This one was easily identified as Acanthocephala terminalis, (AT). The genus name comes from the Greek akanth- 'thorn/spine' + kephale 'head', and refers to the spine on the front of the head.  Terminalis comes from the bright yellow-orange terminal segment of the antennae.

Egg - Click to enlarge
I gently moved the eggs onto the sticky part of a post-it note for handling.  We watched the eggs daily and noticed a change in color on day 16.  They were a little cloudy and had developed some red streaks.  This was a sign on maturation of the larva.  Unfortunately by the next morning the little stinkers had emerged overnight.

Empty eggs - Click to enlarge.
Now we could see the eggs with a lid cut out by the nymph.  The first instar is very distinctive with orange streaks that we had seen through the translucent eggs the day before.  I was amazed that an infant that size can emerge from a tiny egg overnight, but my wife reminded me of how compact our children were packaged before she gave birth.  Once the body of these unfolded their size was mostly the gangly legs.  There are even better photographs on Buggtracks.

The upward curve of the abdomen is common to a lot of different bug nymphs.  As they age by going through sequential molts the later instars of AT darken and develop a spiny back.  There is a series of pictures of one molting at Bugguide.  The one on the right was initially misidentified as an assassin bug nymph.

Later instar - Bugguide

Unlike beetles with their chewing mouth parts, bugs have a proboscis that resembles a hypodermic needle. Their feeding is more complex than just sucking up juices. They first inject their saliva with enzymes into the tissue, then suck up the digested liquid. Assassin bugs attack insects and other prey, while plant bugs like our AT suck the juices of leaves and fruit. It can be difficult to separate some plant bugs from their assassin brethren so it is best not to pick them up with bare hands. Although a few leaf-footed species can be listed as agricultural pests, our AT is not a problem.