Tuesday, 13 September 2016

The Marchantia liverwort.

The tiny Marchantia for me has always had a fascination.  It looks so exotic.   Though the fruiting stems stand less than 4 cms high, they have the appearance of tiny palm trees. The plant has two forms of reproduction.  The 'palm tree' growths carry the sexual organs.  On the wide spreading 'thallus' there are 'gemma cups' easily visible in this photo. These are non-sexual reproductive structures.  The gemmae which develop inside the cups are simply large groups of cells.  They become dislodged with drops or rain and so can be dispersed to grow elsewhere.
The plants are either male or female (dioecious) so that the little palm tree growths carry on the separate plants either the male or the female organs. These called in the male 'antheridia' and the in female 'archegonia' are suspended on the under side of the 'palm like ' 'fronds'.  It is amazing
 to many that the male antheridia produce motile sperm which swim in the raindrops to fertilise the ova in the female archegonia.
After that process has been achieved  tiny capsules grow from the fertilised ova These capsules develop in their interiors tiny spores which eventually may be blown away in the wind to find a new place to grow.
The whole plant carries in every cell nucleus only a half number of chromosomes (haploid). Only the fertilised ovum and the immediate divisions of that ovum have the full double set of chromosomes (diploid).
This photo is of the plant growing in my courtyard, where it can cover a  considerable area.

The Biting Fly Stomomyx calcitrans

 This cursed fly seems to be more common than it used to be.  To the unaided eye it looks like a rather small house fly.  With the aid of a super macro camera one can see more detail. The lower photograph shows the offending proboscis.  It is as hard as horn and can penetrate the soft skin of the human leg with ease, causing much irritation.
It is said that the skin is first cut using the lower lip of the labium and that is certainly how it feels.  The larvae develop in rotting straw or hay especially if it has been used as animal bedding and has been impregnated  with urine. 

Monday, 29 August 2016

The Black Soldier Fly - Hermetia illucens

 The sort of beastie which is a creature that one should really know more about, but one doesn't.
There are quite a few who do know a good deal, however.  Among the avant-garde of gardeners there are those who are quite familiar with this insect.
Its original home is in the continent of America. Now it is probably found world-wide.  Looking up the recorded distribution in France, I find it is recorded in departments along the Atlantic Coast and here and there elsewhere, but not in the Department of the Lot, till now.

This large fly (16 mms long) was sitting on a window frame, looking almost moribund, which it probably was, for the adult only lives a few days.  It cannot eat and is but a reproductive element in the life cycle, in the same manner that exists with mayflies.  I thought at first that it was a species of horsefly (Tabanid) but the length of the antennae seemed to suggest otherwise.  Then what attracted my attention strikingly were the two transparent discs on the forepart of the abdomen. One can see right through the body like windows.
This insect is, as a larva, a maggot, a voracious scavenger of both plant and animal remains.
Further reading tells me that the insect is actually 'cultivated' to reduce compost and food waste.  The larvae can be used as chicken feed and even it is suggested as human food.
The adults live  for a few days, in which they mate, lay eggs and then die.
The references in general say that it causes no disease problems and is probably most useful in clearing up the waste generated by us humans.

Wednesday, 24 August 2016

Grasshopper hunting wasps.

 In late summer when one opens a window, it is not unusual to find the groove at the bottom packed with pieces of cut hay packaging a number of small 'grasshoppers'.  The green insects are in fact 'sauterelles' as the French call them. To create confusion in English they are called crickets, whilst to make that yet more confusing what the French call criquets, the English call 'grasshoppers'.
Wasp hoard of hay and oak-bush crickets
This mass of sauterelles and hay is placed there by a large black and red wasp named Sphex rufocinctus.  The sauterelles are Meconema meridionalis - In English called the southern oak-bush cricket.  This species is quite tiny rarely reaching 15 mms.  Indeed they are small enough to be confused as larval forms. They tend to hide away during the day underneath the leaves of oak, high up in the trees.  
The crickets are paralysed by the wasp. And into this heap of Hay and crickets, the wasp lays about one egg to every four crickets.  After  some short period the eggs hatch and the larvae commence to eat the food stored for them. That you can see in the photo on the right.
These larvae will then pupate first enveloping themselves in silk rather as caterpillars will do.  The firm dark brown pupae will await there till the next spring.

Thursday, 5 May 2016

Another pest from the Far East - Chestnut leaf gall wasps.

Dryocosmus kuriphilus

It looks almost like a Christmas decoration, doesn't it.  But those two shining berry-like structures are a pest from China.  They are galls created by a minute wasp with the jaw cracking Latin name written below the picture.  The wasp is classified in a group known as cynips. Such wasps are about two to three millimetres long and pitch black in colour but with bright orange legs.
 Image of the wasp  taken from the Forestry Commission site, 
and originally courtesy of Gyorgy Csoka, 
Hungary Forest Research Institute, Bugwood.org
The tiny wasp does not reproduce via normal mating.  The females lay eggs in small batches amounting to about 100 eggs at the end of summer. This is without any mating i.e it is parthenogenesis. The eggs are placed just inside the developing winter buds.  The larvae develop slowly and induce the surrounding plant tissues to develop into protective galls. The following summer the adults emerge to infect new buds.
 Gleaning information from the internet one learns that its original home is China, from it spread by 1940 to Japan,  and then to Korea in 1974 and on to the United States. In 2002 it appeared for the first time in Europe. The species has been extensively recorded from Italy since 2005. In 2007 it reached the south of France.
At that time the infested trees were burned but the spread has not been stopped. It has reached England and again burning of trees was tried.  
The pest weakens the trees which must have a toll on both fruit and timber production.
The insect is clearly now widespread through France.
It looks as though it is here to stay.  Just as the Asian hornet is now established and also the Asian Box tree  caterpillar so this Oriental Chestnut Gall Wasp is here to stay.