What's a 'Flat bug'?

If it wasn't for this insect collection I would never have come across this strange insect!  Hiding under the bark of a eucalyptus tree was a collection of flat-looking bugs that I thought had been squashed!  but upon inspection under a microscope I discovered that this was it's natural state.

To find out what this insect could be, my friend photographed it through the microscope and sent it to a colleague who is a forest entomologist by the name of John Bain.  This insect was identified as an aradid bug from the order Hemiptera, from the family Aradidae.  This one is a species in the sub-family Isoderminae. probably Isodermus crassicornis.   Here's the picture:

I wanted to find out some more information on this bug so, as I was given a reference by the forest entomologist, I then began the l..o..n..g process of finding this reference!  The reference was by Prendergast who gave as a source a book published in 1959 by two Americans. This was entitled "Classification of the Arididae (Hemiptera-Heteroptera)".  The librarian at the Lincoln Uni Library eventually found this book hidden in an obscure corner!  Here are some fascinating facts about aradid bugs or 'flat' bugs:

• Key features of the I. crassicornis include rostrum free at base and the wings deciduous, antennae thick with the second segment strongly thickened, forth antennae segment is longer than the third and finally their abdomen is wider than the thorax (see above picture).
• their flattened form and sombre colours are well-adapted for a life on or under the bark of dead trees
• flat bug measures 6.4mm in length and has a depth of 0.10mm!
• their coiled setae are a remarkable adaptation for sucking the juices out of fungi and is more than 6 times as long as the insects body and when not in use is coiled up like a watch spring inside the flat bugs head, as can be seen in the picture below.

• the first of these species was described as early as 1746 by Linnaeus
• the genus Aradus was proposed by Fabricus in 1803
• Aradus is most likely derived from Arados - Greek name of an ancient Syrian city.
• there are about 30 species of aradid bugs found in NZ
• I. crassicornis is a native species and the most commonly found in NZ
• NZ is a natural storehouse of aradid types unequalled by any other continent as they evolved over time from a Carventus-like ancestor

Mating occurs around fungi and or bark, their natural habitat. the male is beneath and to the right of the female. Copulation  can take  between 3 - 8 hours and has been known to go for 24hours! Eggs
(0.45mm-0.86mm) are then laid in frass underneath bark, rotten logs or stumps and could be glued to the surface of the bark or fungi.
The are 5 nymphal instars and nymphs do overwinter with the adults under bark.

if this insect is most commonly found in NZ why have i and others i have spoken not ever seen it before!
if copulation takes that long it must be a mans dream!!
hope you have found this as fascinating as I have!! go forth inspect and explore
amazing insect for its size!

extra information can be read in the following papers.

1. 1965a. The Aradidae of New Zealand (hemiptera, heteroptera) I. Introduction; The Aneurinae. Transactions of the Royal Society of New Zealand, Zoology 6 (5): 53-63.

2. 1965b. The Aradidae of New Zealand (hemiptera, heteroptera) II. The Isoderminae. Transactions of the Royal Society of New Zealand, Zoology 6 (23): 235-243.

3.1968. The Aradidae of New Zealand (hemiptera, heteroptera) III. The Aradidinae and Calisiinae.
Transactions of the Royal Society of New Zealand, Zoology 10 (10): 81-88.