Sunday, July 3, 2011
|Island bluetail damselfly (Ischnura genei)|
It lives in valleys with running water and near ponds, pools and reservoirs.
It is a weak flyer and does not stray too far from aquatic habitats on which it depends throughout its life cycle. Like dragonflies the damselfly lays its eggs in water. The larva spends its entire life under water feeding on smaller organisms.
Two forms of this species are found in two colour forms: green and reddish-brown. Both forms can occur in a particular place and the colour might a result of different environmental temperature during the larval stage of the damselfly.
In other insect species larvae that are developing later in the season, when the temperature is higher give rise to brown adults which are thus better camouflaged in the dry summer vegetation. As far as I know this has not been investigated in damselflies but a future study might show such a link.
Like dragonflies, it has very interesting courtship and mating habits, quite different from that of other insects.
The genital opening is near the tip of the tail, but before mating the male transfers his sperm to an accessory genital organ on the underside of his abdomen, just behind the thorax.
He then finds a female and seizes her by the neck with a pair of claspers situated at the hind end of his body. They then fly in tandem and settle, linked together in this way.
When mating takes place, the female bends her body around under the male’s body and the sperm is transferred for fertilization.
Damselflies and dragonflies use different methods to lay eggs. Some insert them in the plants of aquatic plants or in vegetation at the water’s edge.
Others fly over the water and drop them, while others dip the abdomen into the water to wash the eggs off the tip. Some species remain in tandem whilst the female is laying.
Their larvae or nymphs spend all their time under water hunting smaller animals. A hunting larva stalks its prey to within a centimetre or less, than shoots out the labium and seizes its prey with its claws.
The victims are mostly insects, but large well-grown larvae can even catch tadpoles and small fish. The labium is a segmented organ, found in all insects below the mouth. In dragonfly larvae this organ bears a pair of pincer-like jaws near the tip and is elongated and hinged so that it can be extended in front of the head.
This article was published in The Times on 20.04.2011
|Scilly buttercup (Ranunculus muricatus)|
In Malta it is found in humid valley bottoms such as at Chadwick Lakes and Fiddien. It is an annual or sometimes biennial herb producing a mostly hairless stem up to half a meter long which may grow erect or decumbent along the ground.
The buttercups belong to a large genus of plants that can be found almost throughout the world. It consists of about 400 species some of which are terrestrial while others are aquatic. In the genus, known as Ranunculus, we also find the spearworts, water crowfoots and the lesser celendine.
The name Ranunculus derives from the Latin words rana (frog) and ulus (little). This probably refers to many species being found near water, like frogs. Most buttercup species are poisonous when eaten by sheep, and other livestock but they are left alone because they have a bitter taste and have a blistering effect on the mouth caused by the poison.
Most of the species have bright yellow or white flowers. If the flowers are white they have a yellow center. In many species the petals are highly lustrous making it difficult to photograph them especially in direct sunlight.
In Malta at least 13 species have been recorded some of which are aquatic and can be found floating in pools and streams especially in the numerous small pools found in the rocky habitat known as garigue.
All Ranunculus species are poisonous when eaten fresh by cattle, horses and other livestock but their acrid taste and the blistering of the mouth caused by their poison means they are usually left uneaten. Poisoning can occur where buttercups are abundant in overgrazed fields where little other edible plant growth is left, and the animals eat them out of desperation. Symptoms include bloody diarrhea, excessive salivation, colic, and severe blistering of the mucous membranes and gastrointestinal tract.
When Ranunculus plants are handled, naturally occurring ranunculin is broken down to form protoanemonin, which is known to cause contact dermatitis in humans and care should therefore be exercised in excessive handling of the plants. The toxins are degraded by drying, so hay containing dried buttercups is safe.
This article was published in The Times on 13.04.2011
This species of land snail is found throughout the western Mediterranean. It is common on calcareous soils near the coast and inland. It can be found on soil, in crevices in rocky ground, under stones and among fallen leaves. Sometimes it buries itself in the soil while the specimens I photographed were living on a tree trunk. In the Maltese island it is common on Malta, Gozo and Comino as well as on some of the smaller islands.
There was and probably still is some controversy about this snail in the Maltese islands. Some biologists have listed it as a distinct species endemic to the Maltese island others as a subspecies while others believe that the snails found on Malta are not different enough from the snails found in other parts of the Mediterranean to be considered as a separate species or subspecies.
Pomatias sulcatus is not the only species of pomatias that can be found in the Maltese islands. Another species, Pomatias elegans which is known as the round mouthed snail, can be found at San Anton Gardens at Attard. It probably found its way there on imported plants. This species is common in southern Europe and lives in similar habitats as Pomatias sulcatus.
The pomatias are one of the few groups of land snails that have an operculum. This is a calcareous structure like a small lid that fits neatly in the opening of the shell sealing the soft body inside. The operculum is found in most species of marine and freshwater snails but very rarely in land snails. Its main function is to prevent desiccation especially in those species that live in the intertidal or splash zone of the coast. The presence of an operculum in the pomatias suggests that these snails evolved from marine snails.
This article was published in The Times on 06.04.10
|Ground beetle (Carabus morbillosus ssp. alterans)|
In Maltese the oil beetle is known as dliela żejtnija.
It is normally found crawling in humid areas feeding on vegetation. Its forewings which in most beetles cover and protect the whole abdomen are small leaving the soft elongated abdomen exposed. Compared to most other beetles that are found in the Maltese islands it is big. The female grows up to 30 mm while the maximum length of the male is 21 mm.
Although it has no distinctive warning markings, sheep and I assume goats seem to be aware of its danger. Shepherds have told me that grazing animals sometimes leave a tuft of vegetation uneaten because of the presence of this beetle. According to them if a sheep eats this beetle it immediately becomes bloated and dies.
There are records outside Malta of horses accidentally ingesting a blister beetle (not necessarily a species found in Malta) and dying.
The poison, found in this and other related beetles, is known as cantharidin. This causes blistering of the skin and is used to remove warts although its use is not recommended because of its toxicity.
The poison is generally obtained from a small shiny emerald-green beetle known as Spanish fly which is related to the common oil beetle. The product which is also known as Spanish Fly is given to animals to induce them to mate. Spanish fly has been used by some as an aphrodisiac because during excretion the chemical irritates and stimulates the urethra.
This is a very dangerous practice as the amount used is very small and the difference between an effective and a toxic dose is very small.
Most toxic animals, especially insects, advertise their toxicity by having warning colours which predators learn to leave alone. Wasps have yellow and black stripes. Ladybirds have black spots on a black background and the great ground beetle (photograph) has a shiny violet body and emits a foul smell when threatened.
Until last week very few people were aware of the toxicity of this beetle. One should keep in mind that this is not the only species of poisonous beetle in the Maltese islands. There are another nine species that belong to the same family in the Maltese islands and they are probably as poisonous as the common oil beetle .
This article was published in The Times on 30.03.2011
Saturday, July 2, 2011
|Aleppo Pine (Pinus halepensis)|
The Aleppo pine is normally light green but just now the predominant colour is light brown although its hue varies under different conditions. If seen early on a sunny morning the tree is nearly yellow and shines as if it has a light of its own. When it rains it becomes much darker.
The changes are caused by the appearance on its branches of male and female cones. The cones are the reproductive organs of pine trees.
The male cones produce pollen which is transferred to the female cones so that when it meets the female gametes fertilisation takes place.
On pine trees, the transfer of pollen takes place without the intervention of any animal. Pines rely on wind to carry the pollen from male to female cones.
This is a wasteful method as much of the pollen never reaches its target so the tree has to produce large quantities of very small, light pollen to ensure that at least some of it meets its female counterpart.
When the weather is right, that is, if it has not rained and the air is dry, the slightest breeze is enough to blow the pollen off the male cones. I
f there is no breeze swaying the branch slightly, as what happens when a bird lands on it, is enough to set the release of the pollen in motion. So much pollen can be released every time that this happens that the pollen looks like a small cloud of fine dust.
These changes take place very quickly and do not last long but few people notice them because many of us go through life without being fully aware of our surroundings. Our lives would be much richer if we had to take the time to look around more carefully and become aware of the obvious and the subtle.
This article was published in The Times on 23.03.2011