Halteres help balancing and improve flight. They help flies to perform their fast aerobatics. In addition to providing rapid feedback to the muscles steering the wings, they also help stabilise the head during flight.
They are flapped rapidly and work as gyroscopes, telling the insect about its body position during flight.
Every vibrating object tends to maintain its plane of vibration, a result of the Coriolis effect. If the body of the insect changes direction in flight or rotates about its axis, the vibrating halteres exert a force on the body. The insect detects this force with sensory organs at the base of the halteres.
The two halteres vibrate in different planes, each forming an angle of about 45 degrees with the long axis of the insect. This increases the information got from the halteres.
In Diptera, the formation of the haltere during metamorphosis is dependent on the homeotic gene "Ultrabithorax" (Ubx). If this gene is experimentally deactivated, the haltere will develop into a fully developed wing. This is an excellent illustration of an important mechanism of evolutionary development; a simple homeotic gene change can result in a radically different phenotype.
The Strepsiptera, small insects parasitic on bees, wasps and cockroaches, also have halteres. We know the evolution was independent because in the Strepsiptera the "forewings" evolved into halteres while, in the Diptera, the "hindwings" changed into halteres. This is a classic case of convergent evolution.
Grimaldi and Engel say halteres have evolved at least seven times in insects, and "in most cases it is known to be associated with improved manoeuvering in flight".
Chartres
Chartres is a French commune in the Eure-et-Loir department. About 39,000 people live there.
Chartres is twinned with:
Jethou
Jethou is a small island that is part of the Bailiwick of Guernsey in the Channel Islands. It is privately leased, and not open to the public.
It is immediately south of Herm and has an area of approximately 44 acres (18 ha).
It is said that in AD 709 a storm washed away the strip of land which connected the island with Herm.
The island's name contains the "-hou" suffix, which means "a small island".
In 1416, it became part of Henry V of England's estate. It is still a Crown lease, and is owned by the States of Guernsey.
From 1920 to 1923 it was leased by Compton MacKenzie along with Herm and remained part of that estate for years, although it is currently part of a different one.
The British 1957 musical "Free as Air" by Dorothy Reynolds & Julian Slade was set on the fictitious island of 'Terhou', which was based on Jethou.
On the top is a marker. It is said that in earlier times, pirates were hanged on it with chains, like nearby Crevichon.
From September 1964 until December 1971 the island was occupied by the Faed family consisting of Mr Angus Faed, his wife Susan Faed and their four children, Colin, Erik, Colette and Amanda. Mrs. Susan Faed was the 22nd tenant of Jethou.
It is flanked by two islets, Crevichon to the north and Fauconniere to the south. There is one house on the island and two cottages as well as a large garage where vehicles such as quad bikes and tractors are stored.
It is now leased by Sir Peter Ogden of IT company Computacenter.
Unlike the largely autonomous islands of Sark and Alderney within the Bailiwick, Jethou cannot pass its own laws. It is administered by the States of Guernsey, and elects members to the States of Deliberation as part of the St. Peter Port South electoral district.
At the east of Jethou, puffins can be seen swimming off the rocks.
They also nest there in the east clifftop.
Communes of the Eure-et-Loir department
The following is a list of the 403 communes of the Eure-et-Loir "département", in France.
Lihou
"Not to be confused with Lihou Reef National Nature Reserve"
Lihou () is a small tidal island (95 vergées; 38½ acres; 15.6 hectares) that is part of the Bailiwick of Guernsey, Channel Islands. It lies off the west coast of Guernsey and is the most westerly point in the Channel Islands. Coordinates: . The island was bought by the States of Guernsey in January 1995. Lihou is connected to Guernsey at low tide by an ancient stone causeway between the island and L'Eree headland. It is part of the Parish of St. Peter's. Lihou's bird and marine life makes it an important conservation area.
Like many other Channel Islands, Lihou's name contains the Norman language suffix ""-hou"" of Old Norse origin.
The island has the ruins of the priory of St. Mary which is believed to have been set up by Benedictine monks in the 12th century. The monks of the priory were not very popular with the local people, who thought they were devil worshippers. This animosity may be due to the monks' insistence on rights of wreck. Until 1415 it was under the control of Mont Saint Michel and then Eton College until the Reformation when it was closed and fell into disrepair.
The house on Lihou was used for target practice by heavy artillery during the German Occupation of the Channel Islands during World War II. It has now been rebuilt as accommodation for school groups, and is used as an educational resource.
"Vraic" (seaweed) was harvested and dried on frames set up on the beach. A 1927 factory building produced iodine from seaweed. All traces of the industry disappeared during the German Occupation.
The Lihou family name is included in parish records which go back as far as the early 15th century and there are a number of groups who study the ancestry of the Lihou's. More recently a group was set up using the social networking site 'Facebook' which links Lihou's around the world.
-hou
-hou is a suffix (part added to the end of a word) found in many Channel Islands and Norman names. It is the Norman language version of the Old Norse "holmr", meaning a small island, and often found anglicised elsewhere as "holm". It can still be found in modern Scandinavian languages, e.g. Stockholm.
The Norman "hommet/houmet" also comes from this suffix.
In Parisian French, the equivalent is "îlot", which is the same as the English "islet".
Vergée
A vergée, or vergee, is a unit of area, a quarter of the French acre. Other spellings include vergie and vrégie. It is not an SI unit. The SI unit of area is the square metre.
The term derives from Latin "virga" (rod). Compare French "verge" (yard).
In the Channel Islands, it is a standard measure of land, but the statutory definition differs between the bailiwicks.
In France a vergée was 12,100 square Paris feet (1,276.8 m²). It was 25 (square) perches. The surveying perch measured 22 French feet. the royal perch was 18 French feet.
1 vergée (Guernsey) is equivalent to:
1 vergée (Jersey) is equivalent to:
Derby Industrial Museum
Derby Silk Mill, is a museum of industry in Derby, England. The museum is housed in a historic former silk mill which is part of Derwent Valley Mills. Between 1717 and 1721 George Sorocold built Britain’s first mill beside the River Derwent. This mill was built to produce silk threads using machines powered by a water wheel.
John Lombe copied the design for the machines used for spinning large quantities of silk, when he was working within the Italian Silk Industry. This may be the first example of industrial espionage.
Traditionally the spinning wheel had been used for producing small quantities of silk thread at the homes of local spinsters. But these new, large machines were able to produce far greater quantities of silk and came to compete with the Italians. However, these machines required large buildings and a huge power source. An undershot water wheel turned by the mill fleam on the west side of the new Silk Mill drove these large spinning machines.
John Lombe unnaturally died in 1722. It was believed that he was killed with poison by an Italian as the revenge for stealing trade secrets. His half brother, Sir Thomas Lombe Knt., died on 2 June 1739 leaving his estate to his widow and their two daughters.