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For educational purposes:--

Information on the basics of Entomology

 

Introduction                                                                                                                                                                                                                                                                                         Contents

 

An Introduction To The Study of Entomology 1

Kingdom:  Animalia, Phylum: Arthropoda

Subphylum: Hexapoda: Class: Insecta: Order: Lepidoptera

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General Summary of Lepidoptera


          The name refers to "scaly winged," and there are more than 150,00 species identified.  The fore and hind wings function together.  The butterfly group have a hanging pupal stage or chrysalis, while the moths have a naked pupa or a cocoon.

 

          In the Lepidoptera only a sucking proboscis formed by the maxillae usually represents the mouthparts of the adult.  There are two pairs of membranous wings that are covered with flatten scales, as also is the body.  Metamorphosis is complete.  The larvae are eruciform with chewing mouthparts, with three pairs of legs on the thorax and often five pairs of prolegs on the abdomen.  The pupa is obtect, either enclosed in a cocoon or an earthen case, or free (See Glossary for terminology).

 

          The adults live on flower nectar that they absorb with a specialized proboscis that has been made from the elongated galeae of the maxillae, each being grooved along its inner face and locked to its neighbor.  The laciniae are atrophied and the maxillary palp is regularly greatly reduced. The mandibles are mostly functionless, being fused to the head capsule, and a triangular plate and a pair of large three-jointed palps arethe labium.


          Each half of the proboscis is a tube into which passes blood from the head, and also a trachea and a nerve. Across the cavity of this tube there pass a number of muscles. At rest the proboscis is coiled like a clock spring under the head. When feeding the it is extended and the tip inserted in the food source.   The elastic properties of the cuticular wall of the proboscis accounts for the coiled condition when resting.  The internal oblique muscle of each galea accomplishes an extension of the proboscis. These work together with a stipital valve that controls the closure of the passage between cephalic and galea haemocoeles and causes the proboscis to develop a dorsal keel along its whole length. The attainment and retention of this new shape depends on the turgidity of the galea tube and the elasticity of parts of the cuticular wall. For mechanical reasons it cannot in the keeled position be retained in the coiled state and an extension of the proboscis results (
Borradaile & Potts, 1958).


          During feeding, a complex pharyngeal muscular apparatus causes the fluid food to be sucked into the mouth.  The length of the proboscis in many cases corresponds to the depth of the corolla of the flower which the insect visits, and in the Sphingidae (hawk moths) may be greater than that of the body.  Sometimes the organ is reduced or absent and the animal does not then feed in the adult stage at all (
Borradaile & Potts, 1958).


          The characteristic feature of the wings is their scales.  Enlarged hypodermal cells produce them, and their main function is probably the presentation of color due either to striation of the surface causing interference colors, or to a lesser degree to the pigment they contain.  There are also 'scent scales' which may have a sexual function. Several methods of wing coupling have been

Developed independently in the order.


           
The females of some Lepidoptera, e.g. the winter-moth, Cheimatobia brumata, have totally lost their wings and the insects are confined to the food plant or tree, on which they spend their larval life. The winged male is attracted to the female by scent.


          The larvae have three thoracic and ten abdominal segments with nine pairs of spiracles located on the prothorax and first eight abdominal segments. The mandibles are strong and toothed while the maxillae are stumpy and consist of a cardo, stipes and single maxillary lobe with a two or 3-jointed palp.  The labium has a large mentum, a prementum bearing a median spinneret and small 2-jointed palps.

 

          The thorax has three pairs of legs, and the abdomen five pairs of prolegs on segment 3-6 and 10. Such prolegs are different from the usual insect limbs, being conical and retractile and with hooks on the apex.   In many families there are less than five pairs of prolegs.


          Lepidopterous larvae feed almost entirely on flowering plants with exceptions being the lycaenid caterpillars that feed on aphids or ant larvae, and the micropterygid caterpillars whose diet consist mainly of lichens and mosses. Their digestive enzymes are modified for dealing with plant tissues.


          A cocoon that was previously occupied by the larva usually protects the pupa, which is formed after the last larval molt. In the case of Tortrix moths the cocoon composed of leaves bound together by silk strands. In others, e.g. the silkworm moth, Bombyx mori, it is composed of silk and from it the silk of commerce is prepared. Agglutinated wood particles form a hard cocoon in the puss-moth, Dicranura. In Pieris, the pupa is naked and attached to the substratum by the hooked caudal extremity, the cremaster, and by a delicate belt of silk about its middle. In the more primitive forms (e.g. Micropterygidae) the pupae are free, their segments are free to move and the appendages are not fused to the body. Obtect pupae, in which only a few segments are movable and the appendages are fused to the sides of the body, are most common, e.g. Platyhedra.  Free or incompletely free pupae sometimes emerge from the cocoon before the emergence of the adult.  An armature of hooks and spines often assists emergence, from the cocoon, though the most primitive moths, the Micropterygidae, have pupae with enlarged mandibles. By means of these they bite their way from the cocoon, which is similar to that found in the Trichoptera (
Borradaile & Potts, 1958).

 

          Most Lepidoptera are harmful in the larval stage, few plants being free from their attacks, and some of the world's most serious insect pests, such as the cotton-boll worm, Platyhedra gossypiella, and the gypsy moth, Porthetria dispar, are included in this order. However, some caterpillars have been used as agents in the destruction of invaded cacti in Australia (see ch-87.htm).


          The Lepidoptera are divided into two suborders. In the first of these, Homoneura, the fore and hind wings have venations that are almost identical. To this primitive feature may be added that of the included family Micropterygidae whose mouth parts are mandibulate and the structure of whose maxillae and labium are easily comparable with those of the cockroach. The ghost-moths or swifts (Hepialidae) are also included in this suborder. These nocturnal insects have vestigial mouthparts and short antennae. Their jugate type of wing coupling has already been described. In some species, e.g. Hepialus humuli, the female searches for the male prior to mating. The larvae live in the ground and are white and hairless (
Borradaile & Potts, 1958).


          The second suborder, Heteroneura, is more specialized in that the venation of the hind wing has undergone reduction and so presents a venational pattern very different from that of the Homoneura.  Here are included the majority of moths and butterflies. The families are distinguished largely on venational patterns.


          Among the numerous families of this suborder are the tineid moths, small species still retaining maxillary palpi and possessing narrow fringed wings, with a frenular bristle on the hind wing for coupling.  Tineola biselliella is one of the clothes moths whose larvae can live on the keratin of woolen goods.


          The goat-moths (Cossidae) are large moths without maxillary palps and with a frenular coupling apparatus. They are nocturnal, and lay their eggs on trees. Their larvae tunnel in timber, e.g. Cossus.
Ephestia,
the flour-moth, and Plodia, the meal-moth, are most important as pests of stored products, while Chilo is a form whose larva bores into the shoots of the sugar cane in India. Galleria, the wax moth, able to digest wax after bacteria have broken this down, inhabits beehives in most parts of the world, having become spread by commerce. These belong to the family Pyralidae.
  

          Hawkmoths (Sphingidae) are large, strongly built moths whose fore wings are much larger than the hind ones. A further feature is the obliquity of the outer margin of the wings. The proboscis is long and the antennae, which are thick, end in a hooked tip. Their phytophagous larvae have five pairs of prolegs and usually bear an upturned spine or process on the back of the last segment.

          Of slender build are the geometers (Geometridae). They are weak in flight and a wing-coupling mechanism is not always present. Some species, e.g. Cheimatobia, the winter-moth, are wingless as females. The family gets its name from the fact that in most of the larvae prolegs are borne by the 6th and 10th segments of the abdomen only. Such larvae, therefore, walk by looping the body, bringing the hind segments near to the thoracic and so appear to be measuring distances along the surface walked upon.


          The owl-moths or Noctuidae are the dominant family of the order. They usually fly at night and to this fact is related to their somber coloring which assimilates the insects to their surroundings when resting during the day. The larvae are almost hairless, and in such forms as pupate in the ground the pupa is naked. Tryphaena pronuba, the yellow-underwing moth, is a common species whose larvae devour roots. The larvae of nearly related species, known as cutworms and armyworms, rank among the worst insect pests of North America.


          In the above-mentioned forms, collectively known as moths, the antennae taper to a point and the frenular coupling apparatus is common. The remainder, forming the superfamily Papilionoidea, may be grouped for convenience as butterflies. In these the antennae are clubbed and there is no frenulum on the wings.


          Here are found the whites, e.g. Pieris, the larvae of many of which are restricted to a cruciferous diet, and the 'blues' and 'coppers', in which the metallic coloring on the wings and the shape of the tapering larvae are distinguishing features. There are also the swallowtails, e.g. Papilio, in which the hind wings are commonly extended into tail-like prolongations. Finally may be mentioned the 'skippers', so-called because of their erratic, darting flight quite distinct from the sustained flights of other forms (
Borradaile & Potts, 1958).

 

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Detailed Morphology & Habits

 

          Lepidopteran Wing. -- A jugum is a fingerlike lobe on the forewing that functions to hook the wings together.  It is found in the more primitive Lepidoptera.

 

 

          A frenulum exists as a stout bristle in the male or a bundle of bristles in the female.  This is the more advanced character.

 

 

          Scales are resent on the wings, which may be of various shapes and often overlap.  This arrangement produces colorations.

 

          Mouthparts. -- Adult Lepidoptera possess sucking mouthparts, which appear in the form of a coil.  In some species the mouthparts are nonfunctional or reduced.  Also, rasping spines may be present on the maxillae.

 

          The Larvae. -- The larvae may possess prolegs on the 3-6 and 10th abdominal segments.  These are fleshy outgrowths of the abdomen.  They do not have the characteristic joints of the thoracic legs, but they are movable and are equipped with tiny hooks or crochets on the apex.  When the number of prolegs is reduced, the crochets may remain as remnants in their place.

 

          The Pupae. -- The pupae are obtect and may form a girdle, or a cremaster for suspension.  They may also be enclosed in a silken cocoon.

 

          Moth vs. Butterfly Characteristics. -- According to the pattern and color of adults, moths are mostly drab while butterflies are more colorful.  Butterflies also have clubbed antennae while moths have filamentous or setaceous or plumose antennae.  Butterflies are active in daytime while moths are usually active in twilight or at nighttime.  At rest butterflies hold their wings vertically while moths do so horizontally.

 

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Common Families of Butterflies

 

          The following discussion includes only the most common or important families of Lepidoptera. For greater detail please refer to Borror et al. (1989), and for an expanded treatment of Lepidoptera taxonomy with 125 families noted please see <125 Families>.

 

          The front wings of Lepidoptera males are often diagnostic, enabling a quick means of identification at least to the family level.  The following discussion shows examples of such wings as representative of the family.

 

          Among the common butterflies are the Papilionidae or swallowtail butterflies where an osmatrium is present in the larvae.  The Nymphalidae are often observed but many rare forms are included.  The Subfamily Danainae includes the milkweed or monarch butterfly whose larvae develop on milkweed.  This is one of the few insects that demonstrate migratory behavior.

 

 

          The Pieridae includes the cabbage butterfly, Pieris rapae (L.), where the eggs hatch into greenish larvae.  They attack the foliage of any cruciferous plant.  There may be 3-6 generations per year.  Insecticidal means of control has been required to contain this pest.

 

 

       Another species, the alfalfa butterfly, Colias eurytheme Boisduval, which is native to North America is a direct feeder on alfalfa and related crops.  Control has involved the use of insecticides, insect-attacking viruses and early harvest.

 

 

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Common Families of Moths

 

          The moths contain most economically important species.  The Olethreutidae has the codling moth or apple worm, Carpocapsa (Cydia) pomonella L., with a worldwide distribution.  Larvae feed on all pomaceous fruits such as apples and pears, but only the fruit is attacked.

 

 

          The eggs are laid during the blossoming period or on or near the developing fruit.  The eggs hatch in about two weeks and the larvae are pink in color.  Attack by the first generation causes fruit to drop, while the second generation produces the wormy fruit. Pupation occurs in springtime.  Overwintering is as larvae in a cocoon.  There are 2-3 generations a year and the adult is only about 1.4 cm. long.

 

          Control has involved culling fruit out of an orchard after harvest and the application of insecticides.  Of special interest is the complete absence of this insect in certain geographic areas of western North America, even though host trees are being grown there.  There have been no codling moths found in the Owens Valley of Central California.

 

          Tortricidae -- <Habits>; <Adults> & <Juveniles> -- includes the Mexican jumping bean moth, Lydia saltitans (Westwood), and various forest caterpillars that cause considerable damage.  The wing is notched at the tip.

 

 

          The oriental fruit moth, Grapholitha molesta (Busck) is another serious pest in the family.  It attacks the fruit of peach trees primarily, the injury being similar to that of the peach twig borer.  The larvae are pink in color and feed close to the pit of peach.  However, other kinds of fruit may also be attacked.  Damage is most severe in humid southern regions of North America.

 

 

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          Pyraustidae -- <Habits>; <Adults> & <Juveniles> -- includes the European corn borer, Ostrinia nubilalis (Hubner), which was introduced to North America from Europe in 1917 in broomcorn.  At least two strains have since spread all over the North American continent.  Tremendous damage to maize occurs, as the corn stalk lodges so that mechanical harvesters cannot function and the maize ears often fall.

 

 

          Borer larvae feed on the leaves and surface of maize after which they burrow into the stalk thereby weakening it.  This borer overwinters as larvae in maize stalks and ears in the diapause stage.  One female can lay over 500 eggs.

 

          Control has involved the destruction of maize stubble, late planting, resistant maize varieties, crop rotation and the applications of insecticides.  The addition of the toxin gene of Bacillus thuringiensis into the maize genome has provided containment also.

 

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          Noctuidae (Phalaenidae) -- <Habits>; <Adults> & <Juveniles> -- is the largest family of Lepidoptera that includes the cutworms and armyworms, which are economically destructive.  Cutworms are located underground until the food supply is gone, then they will migrate to feed on the roots.  The armyworms feed on aerial portions of plants.  Their habits are not as secretive as cutworms but they also can ravage crops.  The corn earworm has larvae that feed on the aerial portions of plants, as in the maize ear.  Only one worm is found per ear of maize, the survivor cannibalizes all the others that may have been present.

 

          The corn earworm, Heliothis zea (Boddie) is one of the worst pests in this family that has a worldwide distribution.  It has also acquired the additional names of cotton bollworm, tomato fruitworm, and false budworm relating to the damage it causes.  It is the most important pest of tomato but also attacks lima beans, peppers and eggplant as well as many other crops.

 

 

          There is continuous year-round development in warm climates, but it overwinters as a pupa in colder areas.  It is killed by frost in regions with below freezing temperatures, but it will reinvade again in springtime.  Insecticidal control, whether by direct application or genetic inclusion into the plant genome, has been the only satisfactory means of containing this pest.

 

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          Sesiidae are the clear-winged moths that include the peach tree borer, Synanthedon exitiosa (Say) and Synanthedon spp., cause serious damage by girdling trees.  All members of the plant genus Prunus are affected.  The peak emergence of adults is in mid summer and there is one generation per year.  One female can lay over 800 eggs.  Overwintering is in the larval stage, and pupation occurs in springtime.  Controlling this moth is difficult and requires fumigation in autumn and insecticidal sprays during the growing season.

 

 

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          Geometridae includes the measuring worms or loopers.  Females are apterous.  Banding trees with sticky substances so that the female cannot climb to the tree scaffold best contains them.

 

 

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          Sphingidae are the hawk moths or sphinx moths.  They are very large insects with many patterns on their bodies.  They possess very long tongues that can reach 20 cm.  Charles Darwin hypothesized that orchids were cross-pollinated by a long-tongued insect and later a sphingid moth was found to be the pollinator.  Adults of this family are able to hover, and they are often collected with light traps.  The larvae have a horn on their abdomen and are called "hornworms," even though this horn is not dangerous to handlers.

 

 

          The larvae may cause serious damage to tomatoes, and containment has been through the application of insecticides.

 

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          Saturnidae includes the giant silkworm, the luna moth, Actias luna (L.) and cecropia moth, Hyalophora cecropia (L.). These are very large and attractive moths.

 

 

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          The Microlepidoptera is a group of smaller insects.  The Tineidae includes the clothes moths, Tineola bisselliella (Hummel), whose larvae feed on kerotin, which is present in the form of wool or fur or horn.  They cause considerable damage worldwide and much insecticide has been used for control.  The moths require complete darkness to survive and abatement is possible by storing susceptible items in a lighted area.

 

 

          The Gelechiidae includes the pink bollworm, Pectinophora gossypiella (Saunders), which is especially serious on cotton in North America.  It was first problematic in Texas and Oklahoma but has gradually spread throughout the cotton-growing region.  It is believed to be native to southern Asia.  The insect spreads in cottonseed and overwinters as mature larvae therein.  It can remain dormant for two or more years, and there are 4-6 generations per year.  Control has involved destroying plants in the field and heat treatment of the seed.  The production of cotton varieties containing the toxin-producing gene of Bacillus thuringiensis has also been successful in control.

 

 

          Another important pest of stone fruits in this family is the peach twig borer, Anarsia lineatella Zeller.  It invaded North America from Europe and has spread throughout the continent.  The hairy, banded worms kill tree branch tips in springtime and the fruit sustains the larvae in summer.  In the autumn half grown larvae lodge in the crotch of twigs.  In springtime these larvae feed on plant twigs causing their tips to bend over.  Both twigs and fruit at attacked in summer.  There may be 1-4 generations per year.  Insecticides have been required to contain this insect.

 

 

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          Bombycidae includes the domestic silkworm, which has been propagated for thousands of years by humans in Asia.  The larvae feed on mulberry and related tree leaves.  The larvae are killed while still inside their cocoon after having finished spinning.  Louis Pasteur as a chemist began his interests in biology through the Pebrine Disease of silkworm, which was an epidemic in France.  The pathogen is related to Nosema of the honeybee.

 

 

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Additional LEPIDOPTERA Families

 

Blastobasidae <Habits>; <Adults>  <Juveniles>

Chrysaugidae <Habits>; <Adults>  <Juveniles>

Cosmopterigidae <Habits>; <Adults>  <Juveniles> Cyclotornidae <Habits>; <Adults>  <Juveniles>

Epipyropidae <Habits>; <Adults>  <Juveniles>

Heliodinidae <Habits>; <Adults>  <Juveniles>

Lycaenidae <Habits>; <Adults>  <Juveniles>

Oinophilidae <Habits>  <Adults>  <Juveniles>

Olethreutidae <Habits> <Adults> <Juveniles>

Phycitidae <Habits>; <Adults> <Juveniles>

Psychidae <Habits>; <Adults> <Juveniles>

Pyralidae <Habits>; <Adults> <Juveniles>

 

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Lepidoptera --Biological Control Projects (20.6% of total projects)

 

Brown-tail Moth, Nygmia phaeorrhoea (Donovan) <ch-14.htm>

Carob Moth, Ectomyelois ceratoniae (Zeller) <ch-121.htm>

Citrus Leafminer, Phyllocnistis citrella Stainton <ch-123.htm>

Coconut Moth, Levuana irridescens Bethune-Baker <ch-29.htm>

Codling Moth, Cydia pomonella L. [= Cydia pomonella (L.)] <ch-31.htm>

Colombian Defoliator, Oxydia trychiata (Guenée) <ch-33.htm>

European Cornborer, Ostrinia nubilalis (Hübner) <ch-44.htm>

European Pine Shoot Moth, Rhyacionia buoliana (Schiffermüller) <ch-47.htm>

Grape leaf Skeletonizer, Harrisina brillians B. & McD.  <ch-55.htm>

Gypsy Moth, Lymantria dispar (L.) <ch-60.htm>

Holly Leafminer, Phytomyza ilicis Curtis <ch-63.htm>

Larch Casebearer, Coleophora laricella Hübner <ch-69.htm>

Light Brown Apple Moth, Epiphyas postvittana (Walker) <ch-122.htm>

Mythimna Moth, Mythimna separata (Walker) <ch-75.htm>

Nantucket Pine Tip Moth, Rhyacionia frustrana (Comstock) <ch-76.htm>

Navel Orangeworm, Amyelois transitella (Walker) <ch-77.htm>

Noctuids in New Zealand, Agrotis sp. & Mythimna separata (Walker) <ch-78.htm>

Oriental Fruit Moth, Grapholitha molesta (Busck) <ch-83.htm>

Pink Bollworm, Pectinophora gossypiella (Saunders) <ch-86.htm>

Spiny Bollworms, Earias insulana Boisduval, E. fabia, etc. <ch-100.htm>

Sugar-Cane Borer (Lepidoptera), Diatraea saccharalis (Fab.) <ch-103.htm>

Winter Moth, Operophtera brumata (L.) <ch-114.htm>

 

 

Details of Insect Taxonomic Groups

 

          Examples of beneficial species occur in almost every insect order, and considerable information on morphology and habits has been assembled.  Therefore, the principal groups of insect parasitoids and predators provide details that refer to the entire class Insecta.  These details are available at <taxnames.htm>.

 

 

Introduction                                                                                                                                                                                                                                                                                        Contents

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References