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It’s a growing bug’s world

Figs are popular in Malta with sales of well over 100,000 kilos of early green figs. Right: It remains to be seen whether the Asian tiger mosquito will take over completely from the smaller brown house mosquito.

Figs are popular in Malta with sales of well over 100,000 kilos of early green figs. Right: It remains to be seen whether the Asian tiger mosquito will take over completely from the smaller brown house mosquito.

Birds, plants, fish and molluscs are well studied in Malta but new information keeps flowing in from the diverse world of insects.

Out of 39 insects found on different types of ficus trees, 17 are new records for Malta
- Anne Zammit

Last year’s bulletin (Volume 4) from the Entomological Society of Malta opened another fascinating window on local insect life, with a focus on aphids, moths, butterflies and scarab beetles. For the fifth year running the most recent bulletin (Volume 5, launched in November 2012) begins by shedding more light on fascinating discoveries related to insects associated with ficus trees, among which is the fig tree.

Out of 39 insects found on different types of ficus trees, 17 are new records for Malta. Some of these insects are agricultural pests while others are important for the pollination of these trees.

Ten different species of ficus trees grow in Malta, none of which are truly native. During British rule, the government imported decorative species of ficus from Sicily to plant in streets and squares.

The only productive type of ficus is the fig tree (Ficus carica) which can grow to a height of eight metres and is well loved for its sticky sweet fruit, available for only a very short time in June. Considered to be a ‘false fruit’, the fig is really an accessory in which flowers and seeds grow together to form a single mass. Figs in Malta are a popular seasonal agricultural commodity with sales of well over 100,000 kilos in early green figs. Later crops of purple dry figs during the summer account for tens of thousands more kilos in produce. The tree relies on a particular wasp to pollinate it.

On an international level, only certain insects associated with ficus have been studied so far. New information is now available for these organisms in the local territory by Malta’s entomological society. The study was, in fact, part of a B.Sc. dissertation project by Annushka Falzon supervised by David Mifsud.

The tree’s trunk is delectable to the fig bark beetle. This pest attacks weakened fig trees, accelerates their withering and prevents any recovery of sickly subjects. A description dating back to 1922 notes that there were 32 different varieties of fig trees growing in Malta at the time.

Apart from cultivation, the tree is found growing wild in a number of varied habitats, including maquis, valleys and crevices near cliffs.

The insect species found on ficus trees are grouped according to different ecological regimes with respect to their host plants. Insects found are either wood, leaf or sap feeders.

Another interesting category of insects is represented by the gall (plant cancer) inducers.

The insect forms its own micro-habitat by injecting chemicals to induce a gall in a part of the plant. Such galls can offer food and protection from predators. The larvae develop inside until fully grown then move out of the gall.

Other contributions featured in the society’s bulletin focus on whitefly and sawflies in Malta which have not been studied locally before.

Another group of insects for which almost no information was available in Malta is that represented by plant hoppers, cicadas and related groups with a total of nearly 50 species discovered. Twenty species of flies identified in Malta were reported for the first time in two other contributions.

In the correspondence section, eight papers were accepted for publication, giving information on a variety of topics, in­cluding parasitic wasps useful as biological control agents, food sources of local birds, insects that impact agriculture such as aphids, beetles and mealy bugs, and plant gall-inducing species.

The first incursion of an Asian root mealy bug, Ripersiella planetica, has recently been noted in Malta. A regulated quarantine pest in the EU, the second part of its name comes from the Greek word meaning ‘disposed to wander’.

A revised check-list is included for a species-rich family of wasps that plays an essential role in biological control and in the normal functioning of ecosystems, bringing the total number of species found in Malta to 29.

Another check-list looks at 10 species of parasitic wasps for control of aphids.

Information on the flea beetle, Haltica ampelophaga, newly recorded in Malta, shows the extent of damage to cultivated vines by this pest. A woolly aphid found on pine trees at San Anton Gardens has been added to the growing list of Malta’s aphids.

A small fly with a liking for beeswax has also been newly identified.

A study on insect-eating birds such as the Zitting Cisticola and how they are competing other types of warblers can shed light on the status and distribution of these birds.

Two nests, on untilled land and near carob trees, were selected so that the adult birds could be photographed with food in their bill on the way to the nest, and the insect or spider identified.

The bulletin gives us an inkling of the meticulous work put in by entomologists as they indulge their passion for increasing common knowledge on insects through their laborious research.

Thanks to the efforts of the society’s president, David Mifsud, and many other dedicated individuals we are provided once again with a better understanding of the range and value of our biodiversity.

This latest volume provides information on over 300 insect species inhabiting the natural environment of our islands, with nearly one-third not previously known to live here.

A final section for young entomologists with full-colour plates and in simple but detailed language includes pages on the swallowtail butterfly, emperor dragonfly, Asian tiger mosquito and a fruit fly which attacks olives.

The Asian tiger mosquito is now firmly established in Malta but it remains to be seen whether it will take over completely from the smaller brown house mosquito, Culex pipiens.

The long-horned beetle, another introduced alien (probably entering the country via tree logs intended for timber from central Africa) causes much damage to mulberry trees.

Alien species may have a negative impact as they com-pete with native species which occupy similar ecological niches.

www.entomologicalsocietymalta.org

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