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“Phytopathology, agricultural entomology and applied biology” – M.Ferrari, E.Marcon, A.Menta; School edagricole - RCS Libri spa
Lepidoptera, commonly known as butterflies, include over 100,000 species spread all over the world but especially in tropical regions, where there are species with very showy colors and large sizes (some even reach 30 cm in wingspan). In our country we know about 4000 species of small size (microlepidoptera) and medium (macrolepidoptera). The characteristics that distinguish them from other insects are:
- the presence of wings covered with overlapping scales of various colors, hence the name (lepid = scale, scale);
- the presence of a mouthparts in adults transformed into a proboscis or spiritromba.
The head has large compound eyes, sometimes two ocelli, and antennae of various conformations: feathery, combed, filiform, clavate, etc .; the antennas can be of different shape also according to the sex, and finally the clavate antennas are not generally present in the species with nocturnal habits. The buccal apparatus, of the adult insect, is, in most of the species, suggested (spiritromba); in some primitive Lepidoptera (belonging to the family of Micropterygidae that feed on pollen) the mouth apparatus is chewing. In rest the spiritromba is coiled; when the insect feeds it is unrolled by the pressure of the hemolymph. In some species the spiritromba is very developed and allows to suck the nectar even from particularly deep flowers. In some groups the buccal apparatus is reduced, or absent, so the insect does not feed on the adult stage. The thorax carries: the legs, rather slender and suitable only to lean on the substrate, and the wings (two pairs) membranous and scaly; in some species they are reduced or absent. In most butterflies with diurnal habits, the resting wings are kept in a vertical position, in butterflies with night habits, on the other hand, the wings are folded to the roof on the back or kept in a horizontal position.
Lepidoptera are divided into two suborders according to the characters of the wings:
- Homoneuri: they are more primitive and have wings almost equal in size and ribs;
- Hetoneuri: the front wings are larger and in the hinds the number of ribs is reduced, compared to the front ones. In the Hetoneuri wing, unlike the Homoneuri, the ribs form a large cell, called the discoidal cell, from which the other ribs originate.
The abdomen is made up of nine segments in males and ten segments in females; the females have a replacement ovipositor, formed by the last telescopic retractable segments. In the last uritis, the sexual pheromones (= pheromones) glands blossom which, in virgin females, serve as a call for males (the presence of these pheromones is exploited to set up sexual traps). Males can in turn produce pheromones (aphrodisiac pheromones) which cause females to mate. Generally Lepidoptera are oviparous insects; the eggs can be laid individually or in groups (ovations), glued together and to the substrate by means of substances secreted by the colleter glands. In some cases the eggs are protected by scales or hair from the mother's abdomen. Reproduction is normally amphigonic; in some species parthenogenesis can sometimes appear. Lepidoptera are holometabular insects and some also present hypermetabolia; the larval stages are almost always four or five. The larvae (or caterpillars) are generally polypod; the abdominal pseudo-legs start from the third uritis or from the subsequent urites to the third and, in most species, there are five pairs, rarely more. In certain groups, such as the Geometrids, they are present in small numbers; in many mining microlepidoptera the larvae are devoid of thoracic and abdominal legs (apode larvae). In many species the larva presents the thorax and abdomen covered with bristles and in some species (Limantrie and Processionaria) there are also stinging hairs for defensive purposes. The larvae have 6 ocelli, short antennae and well developed chewing mouthparts. In the larvae the salivary glands are transformed into silk glands. The pupa, with the exception of the primitive Micropterygidae in which it is exarata, is obtecto type and is called chrysalis. The cocoon, if present, can be made up exclusively of silk, as is the case with the silkworm (Bombix mori L.), or silk mixed with excrement and debris (earth and browning materials). The adults, in most species, feed on the sugary liquids of the flowers (nectar); some Lepidoptera, however, are able to suck up liquid substances, piercing the fruits. Some species feed on animal liquid secretes, and finally, the well-known dead head Sphinx is able, through the pointed and rigid spiritromba, to prick the cells of the bees and suck their honey.
In Lepidoptera, the harmful form for agriculture and foodstuffs is the larva. Crop damage is caused by larvae that have a well-developed chewing mouthparts; some species are voracious defoliators. The larvae of certain species feed on fruits, others dig tunnels in the leaves (Mining Lepidoptera), still others dig tunnels in the wood of the trunks and branches (Lepidoptera xylophages).
Some families feed on foodstuffs (flour, grains and derivatives); some species feed on animal substances (wool, skins and preserved animals), others feed on excrement. Finally, there are predatory species of other insects.
Vanessa I or Peacock Eye Inachis io L.- Fam. Nymphalinae (photo www.odezia-atrata.be)
Lepidoptera are often parasitized, at the larval and egg stage, by various Hymenoptera (Braconidae, Icneumonidae, Chalcididae, etc.) and by Larvevoridae Diptera; they can also be prey to several insectivorous birds (woodpeckers, titmouses, etc.), finally the birds and bats are active predators of adult butterflies.
Given the large extension of this order we will analyze the families of agricultural interest; they all belong to the suborder of Heteroneurs and are further divided into two sections: Monotrisi and Ditrisi.
A. Monotrisi section
This section is represented by a small number of primitive species; these are characterized by females having only one genital outlet, with the dual function of mating and laying eggs. The most important family in this section is represented by the Stigmellids.
B. Ditrisis Section
This section includes most of the species of the order; these are characterized by the presence of two separate genital openings: one for coupling and the other for deposition.
Small-sized species (not exceeding 10 mm in wingspan) and with fringed rear wings belong to this family. In most species the larvae are leaf miners; they attack various arboreal deciduous trees including fruit trees.
- Leucoptera malifoliella Costa (= Leucoptera, Cemiostoma scitella Zell.).
Lithocolletidae or Gracillaridae family
This family includes small species (less than 10 mm wingspan), with thin and long fringed rear wings. The species belonging to the genus Phyllonoricter Hb. (= Lithocolletis) attack various broad-leaved trees (Platano, Alder, Beech, Poplar, Elm, Bagolaro, Querce, Carpini and Robinie) and can also be harmful to fruit trees.
Tineids are small butterflies (they reach about 10 mm in wingspan). The larvae feed on grains or other vegetable or animal substances (hairs, wools, skins, feathers or fabrics) found in domestic environments and in warehouses. The larvae are covered with silky threads, interspersed with the debris in which they live, and subsequently pupate in these species of bags.
Among the various species we remember:
- Nemapogon granella (L.) (= Tinea granella L.) known as false wheat moth.
Hyponomeutids are small butterflies (wingspan varies from 10 to 20 mm), with rather narrow and long front wings, and long fringed rear wings. The larvae generally have gregarious habits in fact they remain associated inside a tangle of silky threads. They can live by feeding on various parts of plants, for example of leaves in which they behave like mining larvae, of buds, of flowers and also of fruits, in which they dig tunnels.
Particularly harmful species belong to the Hyponomeutid family including:
- Prays oleae (Bern.), Tignola dellolivo.
Tortricides are a large family of small butterflies with wingspan that can exceed 20 mm; they have trapeze-shaped front wings, while the rear ones, wider, have a short fringe. The larvae feed on various parts of the plants (leaves, shoots, fruits, seeds and even hypogean parts), gnawing them outside or penetrating inside the affected organ.
The Tortricides group numerous species particularly harmful to agriculture, among which we remember:
- Argyrotaenia pulchellana Haw. known as Eulia of the fruit-bearing and the Vine;
- Archips sp. Hb .;
- Cydia pomonella (L.) (= Carpocapsa pomonella L.), Cidia or Carpocapsa, known as the common apple worm.
Cochilids are a small family of Lepidoptera, similar to Tortricides in both adult and larval stages. The larvae feed mainly on flowers and fruits from the inside. The Moth of the vine belongs to it: Eupoecilia ambiguella (Hb.) (= Clysia ambiguella H.).
Sesidi or Egeridi family
The Sesidi are small and medium sized butterflies (some can even exceed 40 mm in wingspan); characteristics are the wings which for the most part are transparent, due to the loss of the scales that covered them. The body is long and rather showy due to the coloration, in bands, of the abdominal part which ends with a tuft of bristles; these morphological characteristics of the wings, the abdomen and the shape of the body camouflage them with the wasps and with some species of Diptera. The larvae are xylophages; they have five pairs of pseudo-legs and live in tunnels dug in the wood or in the bark of many plants, including fruit trees. Among the species of greatest agricultural interest are those belonging to the genus:
- Synanthedon, including Synanthedon myopaeformis (Bosk.) Or Sesia del melo.
The geometrids are a large family of Lepidoptera, mostly crepuscular, however also diurnal and nocturnal. They vary in size from small to medium (some species even reach 40 mm in wingspan); the wide and delicate wings are characteristic for the triangular shape of the first pair. In some species (e.g. Operophthera bramata) the females have reduced wings. The larvae generally have a thin and elongated body; they carry, in most species, two pairs of pseudo-legs (on the 6th and 10th uritis) for which they move, curving and lengthening the body as if to measure the path they are making; this characteristic movement of the larvae gives its name to the family.
Among the species we remember:
- Operophthera brumata (L.), called winter moth or fruit tree moth.
The Nocturnes are a large family of butterflies, ranging in size from small to medium-large, with typically nocturnal habits. They have the body covered with scales and the chest, very developed, brown in color. The wings are well suited for long flights (some species are migratory); the front ones have gray-brown colors, with dark spots and variegations, the rear ones have lighter shades. The larvae are short and robust, generally carrying five pairs of pseudo-legs; they are almost always hairless and have a green-gray color. Normally they are incrisalidate in the soil.
Nocturnes, often polyphages, come out of the ground, at night, to feed by gnawing vegetables and causing damage especially to the arable land. Among the most dangerous species we remember:
- Agrotis ypsilon (Hufn.) (= Scotia ypsilon Rott.), Nocturnal of the sown.
Taumetopeids are medium-sized butterflies (they can reach a wingspan of 30-40 mm) with nocturnal habits; they are known as processionaries, for the long lines that form the moving larvae. In females, the presence of a tuft of abdominal hair with which the ovature is protected is characteristic. Adults have atrophic spirithromb, therefore they reproduce within a short time from their appearance, therefore they die. The larvae are covered with hairs of two types, of which the short ones arranged in tufts on the abdominal segments are stinging; these can cause serious irritation, even to humans.
The larvae live gregarious, typically moving in procession, they build bulky silky nests on the attacked vegetation; they are voracious leaf strippers. Some species that are particularly harmful to forest plants belong to the family, for example:
- Thaumetopoea pityocampa (Den et Schiff.), The pine processionary.
Limantridae are medium and large size butterflies, with hairy legs and regressed spiritromba.
In many species there is sexual dimorphism. In females, especially in the terminal part. the abdomen is rich in hairs with which the eggs are covered and laid, in plates of a few hundred, on the trunks and branches of the trees to which they are glued with the secretion of the colleter glands.
The wings in females can be atrophic or absent. The larvae, equipped with five pairs of pseudo-legs. they are provided with hairs carried by tubercles; in some species there are tufts of stinging hairs. The pupae are protected by cocoons of silk threads mixed with hair. Limantridae are polyphages and feed on gnawing the leaves of the forest essences (they are defoliating larvae) and sometimes attack even the fruit trees. Among the most important species we mention:
- Lymantria dispar (L.), Limantria or Bombice odd, very polyphagous.
Arctidae family (Arctiidae)
Medium and large sized butterflies belong to this family with habits, almost always, nocturnal; frequently have very showy colors. The front wings are narrower and longer than the rear ones which are ovoid in shape. The larvae carry long tufts and are very agile and quick to move. For the most part, the pupae are protected by a silky cocoon, mixed with hairs; they incrisalidate among the vegetation or in shelters near the base of the plants. The Arctids feed on various herbaceous and arboreal plants, and mosses and lichens are also included in their diet. Crop damage is occasional, however serious infestations have recently been reported by Hyphantria cunea Drury (Ifantria americana or American caterpillar).
Numerous moths that attack cereals, their derivatives and other preserved plant materials, such as dried fruit, belong to this family. Among the phycytids we remember:
- Plodia interpunctella (Hb.), Banded Wheat Tignola.
The dangerous Ostrinia nubilalis (Hb.) (= Pyrausta nubilalis Hb.), Corn borer belongs to this family; in addition to corn and other grasses, it also attacks pepper, beet, tobacco and, in some cases, also vines and apple trees.
Cossides are medium to large sized butterflies with nocturnal habits. The body is stocky and large, the abdomen is hairy and, in the female, generally equipped with a long replacement ovipositor.
The spiritromba is atrophic or completely missing, so the adult does not feed.
The larvae are generally bare and have five pairs of pseudo-legs; The mouthparts are well developed chewing machines. They are normally xylophagous larvae and feed on wood of both epigean and hypogeal tissues. Among the most harmful species we remember:
- Cossus cossus (L.), red Rodilegno or red Perdilegno.
- Zeuzera pyrina (L.), yellow Rodilegno or yellow Perdilegno.
Red Rodilegno adult - Cossus cossus (photo http://home.scarlet.be/entomart)
Red Rodilegno Larva - Cossus cossus (photo Pavel Krasensky)