SCIBERRAS, A. (2013) Fauna regarded as domestic pests in the Maltese islands - The Woodlice

The Woodlice
By Arnold Sciberras

If there is a high level of humidity in your house then one of your residents must be the tank- like packed creature commonly known as the woodlouse. This friend of ours is a crustacean (same group which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles). The latter hosts 50,000 described species till now and Woodlice is just one suborder of this group called Oniscidea within the order Isopoda, with over 3,000 world-wide known species. Generally, woodlice are identified by their rigid, segmented, long exoskeletal and fourteen jointed limb body. The number of local species is still uncertain, but the level of interest is high as some species like Maltese Wood louse, Armadillidium schmalfussi, Hanzir l-Art ta’ Malta and Maltese Cave Dwelling Wood louse, Armadillidium aelleni, Hanzir l-Art tal-Gherien ta` Malta are endemic to our archipelago and the latter, as name implies, is confined to caves.

Woodlice need moisture because they breathe through gill like structures called pseudo-trachea, and thus are usually found in damp, dark places, such as under rocks, wood or in our basements. They are usually nocturnal (night dwellers) and are detritivores, i.e. they feed mostly on dead plant matter, though they have been known to feed on cultivated plants, such as ripening strawberries and tender seedlings. Woodlice are ecologically very important because their mode of feeding ultimately leads to a faster replenishment of nutrients back to the soil. In artificial environments such as greenhouses where it can be very moist, woodlice may become abundant and damage young plants.

As already mentioned, these creatures have a shell-like exoskeleton, which must progressively shed as it grows. The moult takes place in two stages; the back half is lost first, followed by the front half which takes two to three days to shed. This method of moulting is different from that of most arthropods, which shed their cuticle in a single process.

A female woodlouse will keep fertilized eggs in a marsupium on the underside of her body until they hatch into small, white offspring. The mother then appears to "give birth" to her offspring.

Some species of woodlice are able to roll into a ball-like form when threatened by predators, leaving only their armoured back exposed. This ability, or dominant behaviour, explains many of the woodlouse's common names. Woodlice in the genus Armadillidium can roll up into an almost perfect sphere as a defensive mechanism; hence some of the common names such as pill bug or roly-poly. Most woodlice, however, cannot do this.

Metabolic rate is temperature dependent in woodlice. In contrast to mammals and birds, invertebrates are not "self heating": the external environmental temperature relates directly to their rate of respiration. They are generally not regarded as a serious household pest, as they do not spread disease and do not damage wood or structures; however, their presence can indicate dampness problems and their number may become irritating to the house owners.

Woodlice are eaten by a wide range of insectivores, but the only animals known to prey exclusively on woodlice are spiders of the genus Dysdera.

Pill-bugs (woodlice of the family Armadillidiidae) are usually confused with pill millipedes. Although they are distantly related to one another, the two are taxonomically distinct.

Both of these groups of terrestrial segmented arthropods are about the same size. They live in very similar habitats, and they can both roll up into a ball. Pill millipedes and pill-bugs appear superficially similar to the naked eye. This is an example of convergent evolution (the acquisition of the same biological trait in unrelated lineages).

Pill millipedes can be distinguished from woodlice on the basis of having two pairs of legs per body segment instead of one pair like all isopods. Pill millipedes also have thirteen body segments, whereas the woodlouse has eleven. In addition, pill millipedes are smoother, and resemble normal millipedes in overall colouring and the shape of the segments.

Besides the Common Maltese Woodlouse which one may occasionally find in a residence, the Common Woodlouse, Armadillidium vulgare, Hanzir l-Art Komuni is the most familiar one in establishments and unfortunately the one which regarded the most as a pest. These creatures are harmless and also beneficial but are regarded as pests because they tend to congregate in large numbers. On some hose facades each year thousands cover the facades during the evening and then disperse or die out in the morning. This behaviour is still a phenomenon not understood. This species may reach a length of 18 mm, and is capable of rolling into a ball when disturbed. This ability, along with its general appearance, gives it the name pill-bug and also creates confusion with pill millipede species.

This species is able to withstand drier conditions than many other woodlouse species, and is mostly found in calcareous soils or coastal areas. It feeds chiefly on decaying plant matter, but also grazes lichens and algae from tree bark and walls.

It is able to regulate its temperature through its behaviour, preferring bright sunshine when temperatures are low, but remaining in shadow when temperatures are high; temperatures below −2 °C or above 36 °C are lethal to it. The latter is also less susceptible to cold during the night, and may enter a state of dormancy during the winter in order to survive temperatures which would otherwise be lethal.



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SCIBERRAS, A. (2013) Fauna regarded as domestic pests in the Maltese islands - The Myriapods

The Myriapods

By Arnold Sciberras

As someone at home steps on a creature that instantly releases a foul smell, that present organism defiantly belongs to this group on which the article is about. Myriapoda is a group (subphylum) of arthropods( which also includes insects, arachnids and crustaceans) containing millipedes, centipedes, and others. The group has 13,000 species known, all of which are terrestrial (land dwellers). Although their name suggests they have myriad (10,000) legs, Myriapods range from having over 750 in some species to others having fewer than ten legs.

Myriapods have a single pair of antennae and, in most cases, simple eyes. The mouthparts lie on the underside of the head. A pair of mandibles lie inside the mouth. Myriapods breathe through spiracles (holes on the exterior that let air in) that connect to a tracheal system similar to that of insects. There is a long tubular heart that extends through much of the body, but usually few, if any, blood vessels.

During mating, male myriapods produce a packet of sperm, or spermatophore, which they must transfer to the female externally; this process is often complex and highly developed. The female lays eggs which hatch as much shortened versions of the adults, with only a few segments and as few as three pairs of legs. The young add additional segments and limbs as they repeatedly moult to reach the adult form.

Myriapods are most abundant in moist locations, where they fulfill an important role in breaking down decaying plant material, although a few live in grasslands, semi-arid habitats or even deserts. Most species like millipieds eat plant or decaying matter, with the exception of centipedes, which are chiefly nocturnal predators. Pauropodans and symphylans are small, sometimes microscopic animals that resemble centipedes superficially and live in soils. Millipedes differ from the other groups in having their body segments fused into pairs, giving the appearance that each segment bears two pairs of legs, while the other three groups have a single pair of legs on each body segment. Although not generally considered dangerous to humans, many myriapods produce noxious secretions which can cause temporary blistering and discolouration of the skin.

Centipedes make up the order Chilopoda. They are fast, predatory and venomous, hunting mostly at night. There are around 3,300 species .they can range from species not exceeding 12 mm to others which may exceed 30 cm. About 16 species have been recorded from the Maltese islands.. Common encounters can be with the following 3 species:

The Soil Centipede Himantharium gabrielis Xini Tal-Hamrija is quite a docile species and is restricted to soil environments. It is easily found in gardens and under pots. Very beneficial in controlling a number pest species.

The Yellow Banded Centipede Scolopendra cingulata Xini Isfar is one of the smallest members of the scolopendra family at approximately 10-15 cm. They are easily recognized by the alternating bands of black and yellow/gold.

The head of this centipede has a pair of antennae, jaw-like mandibles, and other mouth parts. Each segment has one pair of legs. The front segment has a pair of venomous claws (called maxillipedes) that are used for both defense and for capturing and paralyzing prey. The venom is less toxic than other scolopendrid centipedes, but still quite painful. they are still fast moving and can be aggressive so it's best just to look at these colorful creatures rather than try to handle them.They are mostly nocturnal and opportunistic carnivorous hunters, feeding on a broad variety of ground dwelling insects. Youngsters will eat crickets, or other small insects. Adults will consume almost any creature that is not larger that itself, including large crickets, other large insects, and even small lizards. Prefers out door environments but can be met with in urban areas .it is very beneficial in controlling pest species of other arthropods.

The House Centipide Scutigera coleoptrata Xini Ta`l-Indewwa is unfortunately a well considered pest locally. Originally endemic to the Mediterranean region, the species has spread to other parts of the world, where it usually lives in human homes. This species can live its entire life inside a building, usually the ground levels of homes. They are generally considered harmless to humans. Bites are not common, and the jaws of most house centipedes are not strong enough to penetrate human skin . the latter feed on spiders, bedbugs, termites, cockroaches, silverfish, ants, and other household arthropods. They administer venom through modified legs. These are not part of their mandibles, so strictly speaking they sting rather than bite. They are mostly nocturnal hunters. Despite their developed eyes they seem to rely mostly on their antennae when hunting. Their antennae are sensitive to both smells and tactile information. They use both their mandibles and their legs for holding prey. This way they can deal with several small insects at the same time. They avoid dangerous insects. They also adapted their feeding pattern to the hazard the prey might pose to them. For wasps, they retreat after applying the venom to give it time to take effect. When the centipede is in danger of becoming prey itself, it can detach any legs that have become trapped. They live anywhere from three to seven years, depending on the environment. They can start breeding in their third year. For mating the male and female circle around each other. They initiate contact with their antennae. The male deposits his sperm on the ground and the female then uses it to fertilize her eggs. Some report that the eggs are deposited in the ground and covered with plant matter. This species was observed providing parental care. The female lies on her side cradling her clutch of eggs, and later the larvae. This behavior was reported to proceed for several weeks. The female applies an antifungal secretion by mouthing the eggs. As its diet shows, it is a very beneficial species.


On the other hand most millipedes are slower than centipedes, and feed on leaf litter and detritus. They are distinguished by the fusion of each pair of body segments into a single unit, giving the appearance of having two pairs of legs per segment. Around 10,000 species have been described, which may represent less than a tenth of the true global millipede diversity .The name "millipede" is a compound word formed from the Latin roots milli ("thousand") and ped ("foot"). Despite their name, millipedes do not have 1,000 legs, although one rare species has up to 750. Common species have between 36 and 400 legs. Most millipedes eat decaying leaves and other dead plant matter, moisturising the food with secretions and then scraping it in with the jaws. However they can also be a minor garden pest, especially in greenhouses where they can cause severe damage to emergent seedlings. Signs of millipede damage include the stripping of the outer layers of a young plant stem and irregular damage to leaves and plant apices. Very few species are carnivores.

The millipede's most obvious feature is its large number of legs. Having very many short legs makes millipedes rather slow, but they are powerful burrowers. With their legs and body length moving in a wavelike pattern, they easily force their way underground head first. They also seem to have some engineering ability, reinforcing the tunnel by rearranging the particles around it. Their bodies have segmented sections which makes them move in a wave-like form.

The head of a millipede is typically rounded above and flattened below and bears large mandibles. The body is flattened or cylindrical, with a single chitinous( what their outer body is made of) plate above, one at each side, and two or three on the underside. In many millipedes, these plates are fused to varying degrees, sometimes forming a single cylindrical ring. The plates are typically hard, being impregnated with calcium salts

Unlike centipedes and other similar animals, each segment bears two pairs of legs, rather than just one. This is because each is actually formed by the fusion of two embryonic segments, and is therefore properly referred to as a "diplosegment," or double segment. The first few segments behind the head are not fused in this fashion, and the first segment is legless, while the second to fourth have one pair each. In some millipedes, the last few segments may also be legless. The head contains a pair of sensory organs known as the tomosvary organs. These are found just posterior and lateral to the antennae, and are shaped as small and oval rings at the base of the antennae. They are probably used to measure the humidity in the surroundings, and they may have some chemoreceptory abilities too. Millipede eyes consist of a number of simple flat lensed ocelli arranged in a group on the front/side of the head. Many species of millipedes, such as cave-dwelling millipedes, have secondarily lost their eyes.

Male millipedes can be differentiated from female millipedes by the presence of one or two pairs of legs modified into gonopods. These modified legs, which are usually on the seventh segment, are used to transfer sperm packets to the female during copulation. A few species are parthenogenetic, having few, if any, males.

Females lay between ten and three hundred eggs at a time, depending on species, fertilising them with the stored sperm as they do so. Many species simply deposit the eggs on moist soil or organic detritus, but some construct nests lined with dried faeces.

The young hatch after a few weeks, and typically have only three pairs of legs, followed by up to four legless segments. As they grow, they continually moult, adding further segments and legs as they do so. Some species moult within specially prepared chambers, which they may also use to wait out dry weather, and most species eat the shed exoskeleton after moulting. Millipedes live from one to more than ten years, depending on species.

Due to their lack of speed and their inability to bite or sting, millipedes' primary defense mechanism is to curl into a tight coil — protecting their delicate legs inside an armored body exterior. Many species also emit poisonous liquid secretions or hydrogen cyanide gas through microscopic pores along the sides of their bodies as a secondary defense. Some of these substances are caustic and can burn the exoskeleton of ants and other insect predators, and the skin and eyes of larger predators As far as humans are concerned, this chemical brew is fairly harmless, usually causing only minor effects on the skin, the main effect being discoloration.

Around 15 species of millipedes are known to occour locally. The most common home encounter is The Common Millipede Pachyiulus flavipes Hanex ta`L-Indewwa or Tad-Djar is found in most local establishments where high level of humidy persists. They can be handled, and are quite docile and slow moving. This species like most have two main modes of defense if they feel threatened: curling into a tight spiral exposing only the hard exoskeleton, and secretion of an irritating liquid from pores on their body.

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SCIBERRAS, A. (2013) Fauna regarded as domestic pests in the Maltese islands - The Hymenopteriods

The Hymenopteriods

By Arnold Sciberras

If you bug their house which is generally built on or under yours, they will sting you. If they don’t sting you, they will invade your property with their large numbers of individuals. Wasps, bees and ants (collectivly known as hymenopterods) are the creatures this article is dedicated for.

Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees, and ants. There are over 130,000 species described with many others remaining to be. It is yet unknown how many species exist in the Maltese Islands as new species are found frequently but a very rough estimate from local literature indicates that till 1995 over 178 species comprising of 113 species of wasps, 46 species of bees and around 52 species of ants were already known locally. A number of these are endemic species such as the Maltese Slave Keeping Ant (Strongylognatus insularis) Nemlu ta’ Kemmuna, which is not only endemic to the Maltese archipelego but strictly to Comino Island.

Females typically have a special ovipositor for inserting eggs into hosts or otherwise inaccessible places. The ovipositor is often modified into a stinger. The young develop through complete metamorphosis — that is, they have a worm-like larval stage and an inactive pupal stage before they mature.

Hymenoptera vary from medium-sized insects to larger ones and usually have two pairs of wings. Their mouthparts are created for chewing, with well-developed mandibles. Many species have further developed the mouthparts into a lengthy proboscis (like butterflies), with which they can drink liquids, such as nectar. They have large compound eyes, and typically three ocelli.

In the more primitive hymenoptera, the ovipositor is bladelike, and has evolved for slicing plant tissues. In the majority, however, it is modified for piercing, and, in some cases, is several times the length of the body. In some species, the ovipositor has become modified as a stinger, and the eggs are laid from the base of the structure, rather than from the tip, which is in turn used to inject venom. The stinger is typically used to immobilise prey, but in some wasps and bees may be used in defence.

The larvae of most hymenoptera, however, closely resemble maggots, and are adapted to live in a protected environment. This may be the body of a host organism, or a cell in a nest, where the adults will care for the larvae. Such larvae have soft bodies with no limbs. They are also unable to defecate until they reach adulthood due to having an incomplete digestive tract, presumably to avoid contaminating their environment.

Among the hymenopterans, sex is determined by the number of chromosomes an individual possesses. Fertilized eggs get two sets of chromosomes and so develop into females, while unfertilized eggs only contain one set (from the mother), and so develop into males; the act of fertilization is under the voluntary control of the egg-laying female.

Different species of hymenoptera show a wide range of feeding habits. The most primitive forms are typically herbivorous, feeding on leaves or pine needles. Stinging wasps are predators, and will provide their larvae with immobilised prey, while bees feed on nectar and pollen.A number of species are parasitoid as larvae. The adults inject the eggs into a paralysed host, which they begin to consume after hatching.

True wasps, bees, and ants together make up the suborder Apocrita, characterized by a constriction between the first and second abdominal segments called a wasp-waist (petiole), also involving the fusion of the first abdominal segment to the thorax (second part of the body). Also, the larvae of all Apocrita look exactly like maggots.

The term wasp is typically defined as any insect of the suborder mentined above that is neither a bee nor ant [1]. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their numbers, or natural biocontrol. Parasitic wasps are increasingly used in agricultural pest control as they prey mostly on pest insects and have little impact on crops.The various species of wasps fall into one of two main categories: solitary wasps and social wasps. Adult solitary wasps generally live and operate alone, and most do not construct nests (below). All adult solitary wasps are fertile. By contrast, social wasps exist in colonies numbering up to several thousand strong organisms and they build nests – but in some cases not all of the colony can reproduce. In the more advanced species, just the wasp queen and male wasps can mate, whilst the majority of the colony is made up of sterile female workers.

Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. There are several different types of bees and in lame terms they are categorised as: (a) sting less bees; (b) honey bees; (c) solitary and communal bee; (d) cleptoparasitic bees and (e) nocturnal bees. Obviously not all caterogerios exists locally.

Ants are distinct from other insects in their appearance in having elbowed antennae, and a strong constriction of their second part of their abdomen. Many animals can learn behaviours by imitation but ants may be the only group apart from mammals where interactive teaching has been observed. A knowledgeable forager of a particular ant (Temnothorax albipennis) leads a naïve nest-mate to newly discovered food by the process of tandem running. The follower obtains knowledge through its leading tutor. Both leader and follower are acutely sensitive to the progress of their partner with the leader slowing down when the follower lags, and speeding up when the follower gets too close.

Although many species are regarded as domestic pests, nearly none have proved to be an actual pest (e.g. carrying disease, etc) but their persistance in numbers is genrally regarded as a niusance to the owner of the establishment.

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SCIBERRAS, A. (2013) Fauna regarded as domestic pests in the Maltese islands - The Fleas

The Fleas
By Arnold Sciberras

As if a long day at work isn’t enough. You arrive home and immediately try to relax a bit on the couch. The areas where your socks end on your legs start itching. You quickly realize you are not alone….you are accompanied by a creature this article is dedicated for.

‘Flea’ is the common name for insects of the order Siphonaptera which are wingless insects with mouthparts adapted for piercing skin and sucking blood. Fleas are external parasites, living on the blood of mammals (including humans) and birds. In the past, it was most commonly thought that fleas had evolved from the flies (Diptera), based on similarities of the larvae. Now it is more certain that they are descendants of the Scorpionfly family Boreidae, which are also flightless. There are around 2000 species of fleas known worldwide and the number of local species is yet to be determined.

Fleas are small, agile, usually dark coloured (for example, the reddish-brown cat flea), wingless insects with tube-like mouth-parts adapted to feeding on the blood of their hosts. Their legs are long, the hind pair well adapted for jumping vertically up to 18 cm and horizontally up to 33 cm. This is around 200 times their own body length, making the flea one of the best jumpers of all known animals (in comparison to body size), second only to the froghopper. Their bodies are laterally compressed, permitting easy movement through the hairs or feathers on the host's body (or in the case of humans, under clothing). The flea body is hard, polished, and covered with many hairs and short spines directed backwards, which also assist its movements on the host. The tough body is able to withstand great pressure, likely an adaptation to survive attempts to eliminate them by such as mashing and scratching. Even hard squeezing between the fingers is normally insufficient to kill a flea.

Fleas are insects that carry out complete metamorphosis, which consists of four stages: egg, larva, pupa and adult. The flea life cycle begins when the female lays the eggs after feeding. Adult fleas must feed on blood before they can become capable of reproduction. Eggs are laid in batches of up to 20 or so, usually on the host itself, which easily roll onto the ground. As such, areas where the host rests and sleeps become one of the primary habitats of eggs and developing fleas. Fleas lay tiny white oval shaped eggs better viewed through a loupe. The eggs take around two days to two weeks to hatch. They are blind and avoid sunlight, keeping to dark places like sand, cracks and crevices, and bedding. The larva is small, pale, has bristles covering its worm-like body, lacks eyes, and has mouthparts adapted to chewing. The larvae feed on organic matter, especially the feces of mature fleas, but also feed on dead insects and vegetable matter.

Given an adequate supply of food, larvae should pupate and weave a silken cocoon within 1–2 weeks after 3 larval stages. After another week or two, the adult flea is fully developed and ready to emerge from the cocoon. They may however remain resting during this period until they receive a signal that a host is near - vibrations (including sound), heat, and carbon dioxide are all stimuli indicating the probable presence of a host. Fleas are known to overwinter in the larval or pupae stages.

Once the flea reaches adulthood its primary goal is to find blood as it is the only diet for adult fleas. Adult fleas only have around a week to find food once they emerge, though they can survive two months to a year between meals. As previously mentioned, adult fleas must feed in order to reproduce. A flea population is unevenly distributed, with 50 percent eggs, 35 percent larvae, 10 percent pupae, and 5 percent adults. Their total life cycle can take as little as two weeks, but may be lengthened to many months if conditions are favorable. Female fleas can lay 500 or more eggs over their life. Adaptation can be clearly observed in Rabbit Fleas (Spilopsyllus cuniculi) Bergħud tal-Fniek. Adult females of this species can detect the changing levels of cortisol and corticosterone, hormones in the rabbit's blood that indicate she is getting close to giving birth. This triggers sexual maturity in the fleas and they start producing eggs. As soon as the baby rabbits are born, the fleas make their way down to them and once on board they start feeding, mating, and laying eggs. After 12 days, the adult fleas make their way back to the mother. They complete this mini-migration every time she gives birth.

Fleas attack a wide variety of warm-blooded vertebrates including dogs, cats, mice, chickens, rabbits, squirrels, rats, ferrets, and humans. The most common species include Cat Flea (Ctenocephalides felis) Bergħud tal-Qtates. The primary host of this species is the domestic cat, but this is also the primary flea infesting dogs in most of the world. The cat flea can also maintain its life cycle on rabbits, rodents, ruminants and humans can be infested or bitten, but a population of cat fleas cannot be sustained by these aberrant hosts. The Dog Flea (Ctenocephalides canis) Bergħud tal-Klieb, is very similar in habit to the cat flea but it is more commonly found in Europe. On the other hand, the Human Flea (Pulex irritans) Bergħud tal-Bniedem, is a cosmopolitan flea species that has, in spite of the common name, a wide host spectrum.

Fleas are a nuisance to their hosts, causing an itching sensation which in turn may result in the host attempting to remove the pest by biting, pecking, scratching, etc the vicinity of the parasite. Fleas are not simply a source of annoyance. Some people and animals suffer allergic reactions to flea saliva resulting in rashes. Flea bites generally result in the formation of a slightly-raised swollen itching spot with a single puncture point at the center (similar to a mosquito sting). The bites often appear in clusters or lines of two bites, and can remain itchy and inflamed for up to several weeks afterwards. Fleas can also lead to hair loss as a result of frequent scratching and biting by the animal, and can cause anemia in extreme cases. Besides the problems posed by the creature itself, fleas can also act as a vector for disease. A very famous example is the Black Death, which killed millions of people in Europe because of a flea species which was common on Black Rats, which acted as a vector for the bacterium Yersinia pestis. Fleas that specialize as parasites on specific mammals may use other mammals as hosts; humans are therefore susceptible to the predation of more than one species of flea.



For more info: http://arnoldsciberras.blogspot.com/ and www.fortpestcontrol.com

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SCIBERRAS, J. & SCIBERRAS, A (2013) Ġnien Il-Libjani, limits of Kordin, Paola, Biodiversity Report.24pgs.