Seed dispersal to germinate away from parent plant

Squirting cucumber (Ecballium elaterium)

Most plants have strategies to disperse their seeds which ensures that they germinate away from the parent plant. 

Seed dispersal is important because most plants have little or no mobility and thus would not be able to colonise new areas and habitats. 

Dispersal is also important as it takes seeds away from areas where they would face stiff competition from plants of the same species.

Plants use both internal and external forces to scatter their seeds far and wide. These include gravity, wind, water, explosive forces, and dispersion by animals including humans. Sometimes dispersal can be by more than one means thus a plant might allow a seed to fall onto the ground so that late it would be carried away by water. This often happens when coconuts fall to the ground along the coast and then carried away when the tide rises.

Some species can forcefully discharge their seeds long over large distances. The seed pods of the bear’s breaches (ħannewija) open with such force that they make a sound like a small pistol shot. 

The squirting cucumber, known in Maltese as faqqus il-ħmir, belongs to the cucumber family. During the summer months it forms a green-yellow fruit about the size of a large olive. 

It gets its name from the fact that when ripe the fruit ejects the seeds out together with a stream of thick liquid. When very ripe the slightest touch is enough for the fruit to explode. 

Children sometimes play with these fruit shooting the seeds and liquid at each other or throwing them in the direction of each other to see them explode and hitting each other with the seeds. 

The liquid that forms in the fruit is highly toxic but it has been used medicinally since classic times. It can act as a laxative and is known as a violent purgative. In parts of Cyprus and Turkey the juice is believed to cure cases of sinusitis, hepatitis and earache.

This article was published in The Times on 24.08.11

The lappet moth family

Lappet Moth (Gastropacha quercifolia)

The lappet is a large moth that is found in all of Europe as well as in northern and eastern Asia. It belongs to a large family of about 2,000 species known as the eggars, snout moths or lappet moths. 

The family is characterised by having feather-shaped antennae, and an atrophied proboscis. The caterpillars are covered in short hair which is used as a defense mechanism as well as to build the cocoon in which they turn into a pupa. Four members of this family have been recorded in the Maltese islands.

The lappet is very common throughout the islands between May and June and from August to October. The caterpillar has decorative skin flaps on some of its legs hence the name lappet. 

It feeds on the leaves of fruit trees and is sometimes considered as a pest. When fully grown the caterpillar descends to the ground and builds a cocoon in which to pupate. The caterpillar is covered in short hair. This hair, together with silk which the caterpillar itself produces is used to build the cocoon.

Female lappet moths are larger than males. They produce a pheromone which smells of charcoal or burnt wood to attract males. When resting, lappet moths are very well camouflaged. They fold their wings in the shape of a tent to look like oak leaves hence its Maltese name werqa niexfa.

In the lappet, the snout, which is a characteristic of members of the snout family, resembles a petiole (the part of the leave attached to the twig or branch). This adds to the resemblance of the moth to a dried leaf and enhances its camouflage.

In the same family as the lappet we also find the oak eggar (baħrija tal-ballut) which is common especially at Buskett and its surroundings, the grass eggar (baħrija tas-silla) which is also common and the lackey moth (malacosoma) which has been recorded in Malta once in 1956. 

This article was published in The Times on 17.08.11

The field bindweed: A bright funnel-shaped attractive flower

Field bindweed (Convolvulus arvensis)

Maltese summers are characterized by high temperatures and lack of rain. Many plants survive this difficult time as seeds. This results in a dry brown countryside. Where it not for the thousands of trees that have been planted during the past fifty years or so it would be very difficult to find any green vegetation. 

Few species of plants are able to flower but those that do immediately catch one’s attention. One of these species is the field bindweed (leblieb tar-raba’). This species grows in fields and gardens from early summer to early autumn. It also grows in similar habitats such as patches of soil in centre strips and along roads.

The flowers of this plant can have different colours. They are usually white or pink but can also be striped white and pink. As practically no other plant is in flower the bright funnel-shaped flowers are very conspicuous and often attract one’s attention to their beauty. Flowers come in a variety of colours, shapes, sizes and scent but their beauty is not there to please us but to attract insects especially bees which are essential for pollination. 

The most attractive part of flowers are the petals which induce insects to land on them and to visit the nectaries from which they obtain nectar.

To make it easier for the insects to locate the nectaries, many flowers have lines or other markings called nectar guides which lead the bees to the centre of the flower where the flowers’ reproductive structures are found. 

Some of the guides are visible to humans while others can only be seen in ultraviolet light which is invisible to humans but which bees can detect. The nectar guides make it possible for the bees to collect nectar faster and more efficiently. This is advantageous for the plant because of more efficient pollination. 

This article was published in The Times on 10.08.11

Moths on the Maltese islands

Moths are far more common than most people believe. They are not as familiar as the closely related butterflies because with the exception of a very small number they are nocturnal insects. They spend the day trying to be as inconspicuous as possible. They often settle on a surface with the same colour as their body, they place the antennae close to their body and keep their wings flat and close to the surface to avoid making a shadow.

Several hundred species of moths have been recorded from the Maltese islands. Some of which are endemic to Malta, that is they are found only on the Maltese islands. Some are very common while others have been seen only once or twice and more species will be added the list as this group of insects is still being studied by lepidopterists.

For many Maltese a moth is a baħrija but for others especially country people who learnt about nature from their parents, moths are known as farfett ta’ billejl (butterfly of the night) or just farfett. For them the baħrija is a hawk moth. 

Moreover the baħrija was associated with either good or evil. If a hawk moth entered a house it meant that somebody was about to die. 

There are several species of hawk moths in the Maltese islands but the one which was believed to be the portent of death was probably the humming bird hawk moth which is known in Maltese as ħabbara (messenger). This species is one of the few day-flying moths and often enters houses.

Many species of moths that are plant pests are known as susa a word that is more widely used for the woodworm (susa tal-injam). 

The caterpillar of these moths lives in the branches, leaves or fruit of plants and like the woodworm feeds on the plant inside which it lives. 

This article was published in The Times on 20.07.2011

Butterfly diversity peaks in June

Butterfly numbers and diversity reach their peak in June. After that month, the number of butterflies in the Maltese countryside start to decrease.

By now, many species have disappeared and will not be seen again, until next spring. At the moment the most common species and the one most likely to be seen is the small white butterfly which happens to be one of the most common butterflies during the rest of the year.

Another common species is the large white butterfly which looks very much like the small white but is usually much larger.

These two species are common because they feed on, among other things, on the leaves of wild and cultivated members of the cabbage family such as cauliflowers, kohlrabi and of course cabbages.

Up to 40 or 50 years ago in some villages in Malta children trapped these butterflies using the same methods that adults used to trap birds.

Their aim was not just to catch the butterflies.

They used to catch them by using very crude methods such as hitting them with a piece of cardboard while they were resting on a flower.

The trapping was a serious exercise which taught them the skills required, later in life, when they would start to trap birds.

In their play they copied adult bird trappers.

They prepared a trapping site by clearing it of vegetation, levelled the ground and removed all stones.

They then laid down two pieces of cloth on the ground. The cloth was attached to two thin sticks to which they attached a long piece of string.

When the string thread was pulled the sticks and cloth flipped onto to butterflies preventing them from escaping.

To make the site more authentic they even had a decoy butterfly attached to a stick by a thread. The stick could be moved up and down by means of a string to make the butterfly flutter as if it was flying. Some boys even had decoy butterflies tied to sticks stuck in the ground around their trapping site.

When caught the butterflies were placed in a carton box or tin can as trophies to be shown to their friends who had also been trapping butterflies.

The best trappers enjoyed a high status and would boast and brag about the number of butterflies they caught and recount stories about the ones that got away...

This article  was published in The Times on 03.08.2011

Rare ferns

Several species of ferns have been recorded from the Maltese islands. Most are rare or very rare. On the other hand one species, the maiden hair fern, known in Maltese as tursin il-bir, is relatively common. It can be found in caves, wells, in valley bottoms and in damp courtyards of old buildings. 

Like many other ferns it thrives in humid habitat away from direct sunshine although some species such as the rusty-back fern (felċi tal ħitan tas-sejjieħ) can live in full sun and requires little humidity. This species is found in Western and Central Europe including the Mediterranean. In Malta it is very rare. The only time I saw it, it was growing on a large boulder in the middle of a dry valley in a spot not reached by the rays of the sun. In some parts of Europe it was used medicinally as a diuretic.

Most other ferns recorded in the Maltese island are also very rare with some species not having been seen for decades. Two or three species are aliens, that is, they were imported into Malta, probably as cultivated species, and can now be found growing wild.

Ferns are primitive plants. They have stems, leaves and roots like other vascular plants but instead of seeds they produce spores and thus do not have flowers. About 12,000 species are found in the world. About twelve have been recorded in the Maltese islands.

The oldest fern fossil records are from 360 million years ago. In geological terms this would be the beginning of the Carboniferous period which lasted until 299 million years ago. The name of this period comes from ‘carbo’ which is the Latin word for coal as during this period many of the coal beds were laid. 

The coal formed because of the appearance on earth of bark bearing trees which found the right climatic conditions for growth and possibly also because the animals and decomposing bacteria which can digest lignin, the main component of wood had not yet evolved with the result that the wood remained on the ground until it was covered by sediment and eventually changed into coal 

This article was published in The Times on 27/07/2011

Watching Cory’s shearwaters

Cory's shearwater (Calonectris diomedea)

This weekend I took part for the second year running in a Birdlife Malta boat trip to watch Cory’s shearwaters off Gozo. Seeing the enthusiasm of the participants while watching the shearwaters brought to my mind pictures I have seen of tourists watching whales in other parts of the world.

Whale watching is attracting millions of people worldwide. The first whale watching trips took place in 1955.

During that year 10,000 persons paid US $ 1 per trip to be able to get close to the whales. 

By 2008 the number of persons watching whales had risen to 13 million. It is estimated that these generated US $ 2.1 billion in tourism revenue annually.

Watching shearwaters in Malta offers an unforgettable experience that is probably as exciting as whale watching. The Cory’s shearwater, known in Maltese as Ċiefa, is a large bird that looks like a long-winged gull. It flies just above the water surface keeping its wings open to make the most out of air currents that form just above the water surface. It is well adapted for life at sea and approaches land only to breed. 

The Cory’s shearwater nests in colonies, usually under boulders or in crevices in undisturbed cliffs. During the day the colonies are very quite and one does not realize that hundreds of birds could be present close by. During the night the colony becomes alive with the loud calls of the shearwaters as these birds visit the nests to relieve their partner and after the eggs hatch to feed the young birds.

At least 5,000 pairs of Cory’s shearwater breed in the Maltese islands. The largest colony is found at Ta’ Cenc in Gozo.

Shearwater watching can become more popular in the Maltese islands and can even attract a good number of specialized visitors to the Maltese islands. Furthermore such activities can help to create more awareness about the Maltese natural environment. 

This article was published in The Times on 13/7.2011