FOR THE YOUNG ENTOMOLOGIST
Blastophaga psenes
♀
Ficus species are mutualistically associated with their host-specific fig wasps (Agaonidae), for pollination. The common figs that most people grow don’t require pollination. But other types, set fruits only after pollination by a very tiny female wasp. This wasp, native to Asia Minor, Blastophaga psenes, live inside fruits of pollen-bearing wild figs called Capri figs, or caprifigs. For this reason the process of fertilizing figs with wasps is called caprification. The presence of this wasp in Malta is documented in several works related to agriculture.
♂
Caprifigs bear three crops of Syconia annually, the mamme, profichi and mammoni, which mature respectively in spring, summer and autumn. In the beginning of the cycle, a mature female pollinator wasp enters a receptacle (“fruit”) through a small natural opening, the ostiole, passes through the mouth of the fig, which is covered by male flowers, and deposits her eggs in the cavity. In depositing her eggs, the female also deposits pollen she picked up from her original host. As the fig develops, the wasp eggs hatch and develop into a larva, while the fig ovule and ovarian tissues become hypertrophic and transformed into distinct “galls”. The Adult male wasps are wingless and emerge before the winged females. The females only are involved at the pollination fig–fig wasp relationship. In commercial edible fig inflorescens, which lack staminate florets, the fig wasp visit the long stylepistillate florets but they are not receptive to parasitism by the wasp larvae.
Blastophaga psenes
Alessio Vovlas & Nicola Vovlas
Ovule gall
146
Wild fig
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FOR THE YOUNG ENTOMOLOGIST
Trithemis annulata Dragonflies and damselfies are medium- to large-sized, primitive insects that belong to the order Odonata. They are very fast fliers and voracious predators, with streamlined bodies, front-facing legs and eyes with a vision span of virtually 360 degrees in order to spot and capture prey easily. The violet dropwing, or violet marked darter, Trithemis annulata is a species that belongs to the family Libellulidae, it is a widespread and common species throughout Africa, the middle East, Arabia and Western Asia. It was first recorded on the Maltese Islands in 2004 and has since been frequently observed, often in rather large numbers in different locations. The species typically frequents standing water bodies such as pools and ponds, although it has also been spotted around slow moving stretches of water.
Exuvia
Trithemis annulata female
The violet dropwing is a medium sized dragonfly (body length 33-38 mm) with a very distinctive coloration. The red body of the males tends to develop a bluish powdery deposit, typical of many Libellulid species, referred to as pruinosity. The effect of this deposit is to give the specimens a violet–purplish hue, which may become intense if the specimen is old. Wing venation in males is red. Females are yellowish - olive in colour. Wing venation in females is amber. Males of this species are territorial. They establish their territories around water ponds and pools while waiting for females to visit in order to mate. After this happens the females patrol the nearby water bodies where they deposit their eggs. The larvae which hatch from the eggs have a compact body shape. They live in the water until they reach the final instar stage. Larvae are predators and constantly survey the pond bed to capture prey such as mealworms, bloodworms, and mosquito larvae. As in all dragonfly species, when the larvae reach the final instar, they climb up stalks protruding out of the water, moult and develop into teneral adults, leaving behind an empty skin or exuviae. Although physiologically developed, these specimens are sexually immature, rather pale in colour and usually spend time hunting prey, often away from water sources, in order to build nutrient reserves needed during the mating period. Godwin Degabriele
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Trithemis annulata male 149
FOR THE YOUNG ENTOMOLOGIST
Hermetia illucens Hermetia illucens belongs to the family Stratiomyidae (Diptera) popularly known as Soldier Flies, nine species of which are known from the Maltese islands. Soldier flies vary in size from small to large, and they are often strikingly white, yellow or green patterned, sometimes with a metallic sheen. The larvae of many species are aquatic, but many live in terrestrial habitats. Adult flies feed on nectar and often visit flowers. Hermetia illucens popularly known as the Black Soldier fly is a large, striking insect which closely resembles a wasp in habitus and colouration and is often mistaken for one. Originally from South America, it has been spread to most parts of the world by commerce on account of its being able to develop in a wide variety of decaying matter. Eggs are laid in cracks near or on decomposing dung, carrion, compost and garbage. The larvae feed voraciously, and are effectively used commercially in manure management, for both house fly control and reduction in manure volume. The mature larvae and prepupae raised in such operations are themselves used as food supplements particularly in aquaculture. Larval development takes about 14 days. Adult flies do not feed, relying on the large fat body accumulated from the larval stage. Adult males are territorial, and defend their territory from invading males.
Puparia
In Malta, Hermetia illucens was first recorded in 1936, but this appears to have been an isolated finding as the fly was not seen again until 1995. Since that time, it has become a fairly common visitor to houses and gardens, where it can often be seen flying slowly with a loud buzzing sound, or else sunning itself on foliage or walls, in summer and autumn. Paul Gatt
Hermetia illucens 150
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FOR THE YOUNG ENTOMOLOGIST
Icerya purchasi Icerya purchasi is a scale insect commonly known as the cottony cushion scale. Scale insects belong to the Superfamily Coccoidea in the Order Hemiptera. They spend most of their life attached to their host plant sucking its sap, and as a result are very vulnerable to predators. They counter this by secreting some sort of defensive shield either in the form of a hard scale or else as a layer of wax. Icerya purchasi is native to Australia. The cottony cushion scale is quite polyphagous having been recorded from numerous tree species with a marked preference for citrus and Pittosporum. The insect spread rapidly to other parts of the Southern Hemisphere and it soon became a very important pest of the citrus plantations in Florida and California. It now has a widespread world distribution wherever citrus trees are cultivated and is still rated as a major pest causing severe damage to the citrus industry. When the scale insect reached California towards the end of the 19th Century, it posed a grave threat to the new citrus industry. In order to control it the California Department of Agriculture imported a ladybird, known as the vedalia beetle (Rodolia cardinalis) from Australia. This ladybird is a voracious predator of the cottony cushion scale and it soon set about saving California’s orange trees from the new pest. This is recorded as one of the first successful examples of Biological Control, in which pest insects are controlled by insect parasites or predators.
Rodalia cardinalis
Icerya purchasi Professor John Borg
Icerya purchasi first reached Maltese shores from Sicily in 1907. Four years later Professor John Borg imported the vedalia beetle from Portici in Naples and embarked on a successful programme of biological control. The ladybird soon became established and it is now quite common, still making its contribution to reducing the damages caused by Icerya. The adult female is at first a reddish insect about 5 mm long, but it soon starts extruding wax, forming a fluted egg-sac which eventually exceeds the length of the insect itself. This egg-sac contains up to 1000 red eggs which soon hatch to give rise to the motile first instar larvae termed crawlers. These move around looking for a suitable place to settle and soon develop into adult females. David Dandria 152
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FOR THE YOUNG ENTOMOLOGIST
Zizeeria knysna Commonly known as the African grass blue, Zizeeria knysna is a tiny butterfly (18-24 mm in wing span) that is often very common where found. It belongs to the butterfly family Lycaenidae. It is always associated with damp places, usually with lucerne or mint, such as irrigation ditches or drains and desert oases. The butterflies are very fond of lucerne fields. This butterfly is a rare species in the Maltese Islands breeding in a few isolated locations. In Malta the species was recorded from Wied Żembaq, Birżebbuġa, Għadira, Wied Qirda, San Gwann, Chadwick Lakes, and from Ħondoq ir-Rummien in Gozo. Locally this species feeds on the Common knotweed, Polygonum arenastrum, a plant found in a variety of habitats. The species is known from a number of South European and Mediterranean counties, Africa, Tropical Asia and Australia.
Larvae and pupae
The species is on the wing in autumn and goes through a number of generations until winter time when temperature cools down. Upperside of male forewing, violet blue with wide dark marginal borders, otherwise unmarked. Underside pale fawn with discal and marginal markings in slightly darker shade of fawn. Female upperside brown with restricted and variable patches of blue above inner margins of both wings. Underside as male. The larva is of a green or brown coloration. Sometimes larvae are ant-attended because of honeydew secretions which the larvae produce. Aldo Catania
Zizeeria knysna 154
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FOR THE YOUNG ENTOMOLOGIST
Eurynebria complanta Eurynebria complanata belongs to a group of beetles, commonly known as ground beetles (Carabidae) and represented in the Maltese islands by about 150 different species. This species is highly specialized, inhabiting sandy beaches of the Mediterranean basin and those of the Atlantic Ocean. It is a strictly nocturnal predator and its preferred food source includes juvenile sand-hoppers. Being a fast runner it is capable of moving long distances along the strand line which is delimited by the highest point that waves and tides reach. This area generally holds rotting seaweed and other debris that is washed ashore, and this detritus is the habitat and daytime refuge of Eurynebria complanata. The same habitat is also shared by sand-hoppers and other arthropods. Eurynebria complanata is considered as a good biological marker on sandy beach ecosystems. Relatively common in the past, this species is becoming scarcer due to sea pollution that affects it main food source, the continuous pressure from beach users and the mechanical cleaning of the beaches that has a negative influence on the biological cycle of its prey and the habitat of the beetle itself. Once present in most coastal areas of Italy, it is now restricted to very few undisturbed sandy beaches. In 1907, Eurynebria complanata was first recorded from Melli침a bay in Malta. The species was reported again from Ramla in Gozo in 1998 probably on material collected in the 70s or 80s. In recent years the species was never found again in sandy beaches of the Maltese islands and most likely the species is locally extinct.
Eurynebria complanata
Henry Borg Barthet
Larva 156
Ramla Bay 157