The white wall rocket

The white wall rocket is a very common annual plant. It grows in disturbed habitats such as uncultivated fields and roadsides. Despite or because of the fact that it is very common few people actually take enough interest to look closely at the flowers.

The flowers are white sometimes with a tinge of violet. Their structure is similar to that of other members of the mustard family to which the rockets belong. It is made up of four petals arranged in the form of a cross. The family is also known as the crucifers, meaning cross bearing, or sometimes as the cabbage family.

After having lain dormant for a whole summer, the seeds of the white rocket sprout quickly soon after the first autumn rains. Within weeks the plant starts flowering.

The white rocket is native to southern Europe and the Mediterranean. Probably as a result of climate change it is now found further north and has even reached southern England.

The crucifer family is of importance because several species have been cultivated for thousands of years. 

Members of the family include the cabbages, broccoli, cauliflower, turnip and mustard. The leaves of the white rocket are similar to those of the cultivated rocket and they are sometimes added to salads to add a spicy taste. The leaves are said to have diuretic properties but it seems that the plant is not used medicinally.

Many species of crucifers are food plants for the caterpillars of various species of white butterflies including the small and cabbage whites which can become pests of cultivated plants.

Members of the crucifer family are characterised by fruit in the form of a capsule known as a siliqua. The siliqua is an elongated structure with seeds inside. The capsule breaks open along a line of weakness in dry condition. In some species the siliqua breaks open explosively and the seeds are thrown far and wide away from the parent plant.  

This article was published in the Times of Malta on 18 December 2013.

The yellow-legged gull

An injured yellow-legged gull found at Għadira Bay last Sunday.

I regularly visit the Ghadira Nature Reserve to check what birds are present and to take pictures. Last Sunday as soon as I got there a man came to the reserve’s reception centre and informed the weekend wardens that there were two large birds on the beach. One had a broken wing and could not fly and the other was dead. 

One of the young wardens immediately went to the beach to save the injured bird, an immature yellow-legged gull as was the dead bird. The injured bird was picked up and taken to the reserve so that it would be taken to a vet.

The day before this incident somebody went to the reserve to inform the warden that he saw two hunters shooting at gulls from a boat in the bay.

The yellow-legged gull has been protected by Maltese law for over thirty years. It is illegal to shoot at them kill them or harm them in any way.

The yellow-legged gull is a large bird. Males can have a wingspan of over one and a half metres.

Adults are recognised by their silvery grey back and upper wings. Immature birds are mottled grey and can be confused with other similar species. The yellow-legged is the only gull likely to be seen around the Maltese islands during the summer months.

The yellow-legged is Malta’s largest breeding bird. The largest colony is found on the plateau of the small island of Filfla. Other colonies can also be found along the cliffs in both Malta and Gozo.

It is only recently that the yellow-legged gull started to be recognised as a separate species. In previous year, it was considered as a subspecies of the herring gull. The herring gull is a similar gull but adults have pink instead of yellow legs. At one time the yellow-legged gull was assumed to be the same species as the Caspian gull but with the help of DNA analyses it was realised that it is a separate species and is nowadays known scientifically as Larus michahellis. Throughout these changes in scientific classification and common name this species retained its Maltese name, gawwija prima.

This article was published in the Times of Malta on 11 December 2013.

Black-headed gull

To many people in Malta say that there are no birds to see. They could not be more wrong. They only have to visit one of the bays or harbours in winter to watch gulls, terns and other seabirds.

The good thing about gulls and other sea birds is that most of the time they come so close to the shore that they can be observed without using binoculars although a camera is a bonus.

At this time of the year the most common gull and the one you are most likely to see is the black-headed gull.

Black-headed gulls breed throughout most of Europe and Asia as well as along the eastern coast of Canada. Most populations are migratory. Migratory and wintering birds arrive in the Maltese islands in autumn and many remain until early spring. The numbers one can see close to the coast vary from day to day. On calm days they prefer to wander further out at sea but on windy and stormy days they congregate in sheltered areas especially in harbours.

Despite its name for most of the year the black-headed has a white head with a small black spot behind its eyes. It is only during the breeding season that it has a chocolate-brown hood. The Maltese name, gawwija rasha kannella, is a better description as the hood is not black. Sometimes one can see one or two birds in breeding plumage in late February or March before these birds leave for their breeding grounds further north in Europe.

Other species of gulls as wells as terns and the occasional grebe or cormorant can also be seen around the coast.

The Mediterranean gull, which winters in smaller numbers, is known in Maltese as gawwija rasha sewda because its head, face and part of the neck turn black during the breeding season.

The yellow-legged gull, gawwija prima, is much larger and can be seen throughout the year because it breeds in the Maltese islands.  

This article was published in the Times of Malta on 4 December 2013.

A fly to keep away pests

The tachinids are flies belonging to a family known scientifically as Tachinidae.

The tachinid family consists of over 8,200 species. About 1,600 species are found in the Palearctic region, which is the faunistic regionl region in which we live. Just over forty species have been recorded in the Maltese Islands.

The first list of Maltese tachinids can be found in a book on Italian flies written in 1859 by Camillo Róndani, an Italian entomologist noted for his interest in flies.

The author recorded nineteen species of tachinid flies from the Maltese islands. At the time Italian naturalists included the Maltese islands as part of the Italian territory and listed species of  Maltese plants and animals as part of  Italy’s flora and fauna.

Of the nineteen species recorded by Róndani, six are no longer found in the Maltese islands. The disappearance of these species could be due to natural causes but it is likely that it is a result of human activities such as the degradation and destruction of the Maltese countryside. Biodiversity is also reduced by the use of pesticides as well as the burning of vegetation during the summer months.

Fischeria bicolour, the species in the photo, is a member of the Tachinid family. It does not have a common name and is often overlooked by non-naturalists. This species is normally seen on vertical rock faces and on walls.

The larvae of all known tachinids are parasitoids. They live mainly in other insects especially on bees, wasps and ants eventually killing their host.

Tachinids play a major role in the natural control of other species including pests. Some species are used in biological pest control. Many species from around the world have been introduced into North America to control pests.

As adults, tachinid flies are not parasitic. During the adult stage many species do not feed at all but some visit flowers in search of pollen and nectar while others feed on decaying matter. 

This article was published in the Times on 27 November 2013.

The large white butterfly

The large white is one of the most common butterflies to be found in the Maltese islands. The only other butterfly which might be more common is its close relative the small white.

The large white is also known as the cabbage white or cabbage butterfly because its caterpillars feed on members of the crucifer family (or as it is sometimes called the mustard family) to which the cabbage belongs. In Maltese it is known as farfett tal-kabocci.

This species is found throughout Europe, North Africa and many parts of Asia. In 1995 it started breeding in South Africa and in 2010 it reached New Zealand.  It is found mostly in open spaces, farms and vegetable gardens.

Wherever it occurs it is considered a pest because it feeds on cultivated plates such as cauliflowers, broccoli and kohlrabi which belong to the cabbage family.   

Both males and females have white wings with black tips on the forewings but the female has two black beauty spots which the male does not.

The large white is a well-known migrant. It moves both north – south as well as laterally. It is difficult to follow its migration patterns because of the large distances it travels. In Malta it sometimes arrives in large numbers. It migrates in both spring and autumn but most large cabbage white migrations that have been recorded in the Maltese islands took place between September and November.

Most Maltese are not aware of the migration of butterflies. Butterflies do not migrate in a regular pattern and their arrival can never be predicted. Furthermore migratory butterflies were never harvested so there was never any need to await their arrival.

Both adult cabbage whites and their caterpillars have a bad taste which they get from chemicals derived from mustard-oils which they obtain from their food-plants when they are still in the larval stage. The caterpillars are brightly coloured and do not bother to hide themselves as predators tend to avoid them.  

This article was published in the Times of Malta on 20 November 2013.

Plain but beautiful

The past week was noted for the arrival in the Maltese islands of a non-resident butterfly – the plain tiger or as it is sometimes known the African monarch.

The plain tiger is widespread and common in Africa and Asia as well as on most of the islands of the south Pacific, and across much of Australia.

By butterfly standards it is considered as a medium-sized butterfly but compared to the butterflies found in the Maltese islands it is definitely a large butterfly. ts body is black with many white spots but anybody spotting this butterfly is more likely to see it flying or resting on a flower with its wings open. In this case one would see the tawny and black upper wings and perhaps the series of white spots on the hindwing.  

The plain tiger is highly migratory. In the Maltese islands it is used to be a very rare visitor but nowadays it is being recorded with increasing frequency and in larger numbers. This could be due to this species expanding its range possibly as a result of climate change.

There are no records of this butterfly ever having bred in the Maltese countryside but this does not exclude the possibility that it could breed or even become a regular breeder in the future especially if the food-plant of its caterpillar, the milkweed, becomes more common.

In Maltese it is known as farfett ta’ danaus, clearly not a folk name but a name given to it by entomologists who made up the Maltese name from its scientific name Danaus chrysippus.

This week’s bad weather might stop the arrival of more plain tigers but more might still arrive as soon as the weather changes It would be very useful if readers email me the records of any plain tigers that they have seen or that they might see in the coming days and weeks. 

This article was published in the Times of Malta on 13 November 2013.

The flesh-eating flies

The flesh-fly is one of over thirty species of flies whose larvae live mostly on living or dead flesh. Like other species of flies they are of medical and sanitary importance mainly because they help in the decomposition of organic matter and cause disease.

In Maltese the flesh-fly is known as dubbiena tal-laħam.

Flesh flies belong to the Sarcophagidae family. The family  name is made up of two Greek words sarco and phage meaning ‘flesh’ and ‘eating’. The word sarcophagus has the same roots.

The flesh–fly family consists of about 2,500 species.

Like other species of flies, flesh-flies are carriers of pathogenic agents especially bacteria, one of which is the bacillum that causes leprosy.

Flesh-flies can also cause myiasis in humans and other vertebrate animals. Myiasis is the term used to describe the invasion of tissues or organs by the larvae of flies. The name of the condition is derived from the ancient Greek word myia meaning “fly”.

Humans can become victims of flesh-flies. The larvae of flies are in fact sometimes used in hospitals to remove dead flesh from patients.

The most common victim are sheep which become host to the larvae of the blowfly. Adult blowflies lay their eggs on the sheep’s skin. When the eggs hatch, the larvae eat their way through the skin and tunnel through the sheep’s flesh causing irritation and unless treated the myiasis can result in the death of the sheep.

Flesh flies are ovoviviparous. Most insects lay eggs which hatch after some hours, days or weeks. Flesh-flies lay their eggs while day are hatching or even allow the eggs to hatch in their body before depositing the larvae onto their preferred food.

Some flesh-flies parasitize other insects such as grasshoppers and solitary bees and wasps. 

This article was published in the Times of Malta on 6 November 2013.