Morphology and Adaptation of Immature Stages of Hemipteran Insects

Home , Cercopidae, Cimicidae, Coccidae, Diaspididae, Hydrometridae, Phylloxeridae

Devina Seram and Yendrembam K Devi

Assistant Professor, School of Agriculture, Lovely Professional University, Phagwara, Punjab

Introduction

Insect Adaptations

An adaptation is an environmental change so an insect can better fit in and have a better chance of

living. Insects are modified in many ways according to their environment. Insects can have adapted legs,

mouthparts, body shapes, etc. which makes them easier to survive in the environment that they live in

and these adaptations also help them get away from predators and other natural enemies. Here are some

adaptations in the immature stages of important families of Hemiptera. Hemiptera are hemimetabolous

exopterygotes with only egg and nymphal immature stages and are divided into two sub-orders,

homoptera and heteroptera. The immature stages of homopteran families include Delphacidae,

Fulgoridae, Cercopidae, Cicadidae, Membracidae, Cicadellidae, Psyllidae, Aleyrodidae, Aphididae,

Phylloxeridae, Coccidae, Pseudococcidae, Diaspididae and heteropteran families Notonectidae,

Corixidae, Belastomatidae, Nepidae, Hydrometridae, Gerridae, Veliidae, Cimicidae, Reduviidae,

Pentatomidae, Lygaeidae, Coreidae, Tingitidae, Miridae will be discussed.

Homopteran families

1. Delphacidae – Eg. plant hoppers

They comprise the largest family of plant hoppers and are characterized by the presence of large,

flattened spurs at the apex of their hind tibiae. Eggs are deposited inside plant tissues, elliptical in shape,

colourless to whitish. Nymphs are similar in appearance to adults except for size, colour, under-

developed wing pads and genitalia.

2. Fulgoridae – Eg. lantern bugs

They can be recognized with their antennae inserted on the sides & beneath the eyes. Some

species are tropical types and are luminous, which secrete large quantities of wax. Eg. wax-tail hopper

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like egg case. Nymphs often form long filaments presumably for protection against predators.

3. Cercopidae – Eg. spittle bugs

Eggs are laid in mass on leaves surface, rounded in shape. Nymphs cover themselves on 7th & 8th

abdominal segments with frothy mass which is a foam made of fluid voided from anus & from a

mucilaginous material secreted by epidermal glands. Through caudal appendages, the air bubbles are

inserted into the foam. Only nymphs are capable of producing foam for protection against other

organisms and to avoid dessication. Adults do not produce foam.

4. Cicadidae – Eg. cicadas

Eggs are inserted into grasses, shrubs, living or dead twigs of trees, which are elongated in shape,

colourless to whitish in appearance. Nymphs can be recognized with massive & enlarged pincher-like

forelegs adapted for digging and grasping. They hatch from the eggs in a month & are dropped to the

ground, the last nymphal instar climbs up on tree where the final moult takes place. The 17-year cicada,

Magicicada septendecim (L.) spends almost 17 years of its life cycle in its nymphal stage.

5. Membracidae – Eg. tree hoppers

Eggs are laid individually or in groups either placed into living tissue of plant or deposited on

surface, overwinter & hatch in spring. Nymphs are dropped to vegetation where they complete their

development. The dorsal sides of thorax in nymphs are covered with tubercles or spines and can be

differentiated from the adults by the absence of pronotal structure, but sometimes formed filaments or

spinose projections on tergites.

6. Cicadellidae – Eg. leaf hoppers

Eggs may either remain dormant for a month to almost a year or develop and hatch within few

weeks. They undergo a series of 5 moults and reach its adult stage. Some special adaptations in nymphs

are presence of jumping hind legs with the hind tibiae having two or more rows of spines, which are

capable of powerful leaps adapted for search of food & avoiding predators; large eyes for excellent visual

and also acts as avoidance from detection or capture by potential predators. Nymphs are also capable of

detecting reflectance spectrum of several colors, with hues of yellow being most attractive. Several

species (e.g. Glassy-winged sharpshooter - Homalodisca vitripennis) have the ability to produce white

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surfaces, females then scrape this material to "powder" the area and cover the eggs for protection and the

process is known as "powdering”.

7. Psyllidae – Eg. psyllids

Psyllids are different from other hemipterans since they are not phloem specialists (feed on xylem

and mesophyll) and therefore they have rudimentary filter chamber and only four Malphigian tubules.

Eggs are pedunculate or stalked and are placed on exposed surfaces of leaves which enables them to draw

water from host plants. The hind legs of nymphs are fitted for leaping and ability to jump high as in

jumping plant lice. Many species produce large quantities of white waxy secretions which resemble

woolly aphids. Nymphs are smooth, possess large wing pads and sometimes have small abdominal

fringes. There are 5 nymphal instars and some species' nymphs live under sugar covers called "lerps,"

while others are gall-enclosed or free-living. Lerps are protection cover formed from sugar and wax

excreted by insects which hardens in contact with air. These lerps vary in size, colour and shape viz.

cones, univalves, bivalves or fan & white to dark brown.

8. Aleyrodidae – Eg. whiteflies

Eggs are pedunculate, connected by a short stalk & deposited in a circle or crescent on the

underside of the leaves. There are 4 larval instars and only the 1st instar is with well-developed legs called

“crawler” and the subsequent instars are sessile. Wings develop internally during metamorphosis. They

differ from other families in the presence of an extra form i.e. the 4th instar forms a "pupal case” or

"puparium" which resembles like the pupa of other holometabolous insects. The nymphs are often mistaken

for soft scales. Thus, they can be differentiated by the presence of vasiform orifice, operculum & ligula.

Sometimes, nymphs and pupae of some species are covered with various types of wax while others are

devoid of wax.

9. Aphididae – Eg. aphids

The most common reproductive strategy in this family is viviparous parthenogenesis alternating

with sexual reproduction (holocyclic). Some of the spp. (esp. crop pest) prevails in warm climate with

anholocyclic life lacking sexual reproduction. In typical life cycle, fundatrix ♀ hatches from the

overwintering eggs. Female fundatrices are those which are viviparous, parthenogenic, often without

wings (apterous) and in turn produce more viviparous and parthenogenic ♀, both with wings (alate) &

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for defense against natural enemies in aphids include secretion of defensive wax fluid (triacylglycerols)

from cornicles. In some species of aphids, whole body is often covered with white waxy fibers secreted

by dermal gland; excretion of honeydew from anus which is produced in sufficient quantity to cause

stickiness on surface to ward off natural enemies. A structural adaptation in myrmecophilous aphids

(aphid species being predated by ants) is the presence of group of setae in anal region to hold honeydew

droplet while the attending ant imbibes it.

10. Phylloxeridae – Eg. phylloxera

Phylloxerids resemble like aphids. These insects overwinter duirng their egg stage. In early spring,

nymph hatches and migrates to developing leaf to feed thus causes irritation in plant tissues ultimately

forming galls. When they are matured, ♀ produces numerous parthenogenetic young ones which will

migrate to other host plants to form new galls. Some nymphs can fall to the ground after a few

generations and burrow into the roots for feeding. The winged adults will emerge from the ground in

mid-summer and lay eggs on vines where they develop into nymphs and adults. Single egg lay again on

the vine after mating, thereby completing its life cycle.

11. Pseudococcidae – Eg. mealy bugs

Some spp. are oviparous (egg laying) and others viviparous (give birth to young ones). Oviposition

take place in a loose, cottony wax called as ovisac. The first instar nymphs are very active and mobile

called ‘crawlers’. After the 1st moult, they lose their legs & antennae and become sessile during

subsequent moults. ♀ excrete large amount of honeydew. In arid regions, excreted honeydew solidifies

on the leaves and accumulates in thick layer forming a sweet, sugar-like material called “Manna”. They

survive and over-winter during cold conditions as eggs in ovisac or other stages. During warm climates,

mealy bugs remain active and reproduce throughout the year increasing its populations.

12. Coccidae – Eg. soft scales

Coccids either lay oval shaped eggs under scale or produce live young ones on vegetation. The

nymphal characters are similar to that of pseudococcidae. Waxy or scale like materials are secreted

covering the body and ♂ develops like ♀ except for the last instar which is quiescent & called as false

pupa. Wings start developing externally within pupal stage itself. In Stellate scale (Vinsonia stellifera,

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body giving them a star-like appearance.

13. Diaspididae – Eg. hard scale

They lay oval shaped eggs in large numbers inside ovisac. The nymphs produce fibrous scale

cover by incorporating the exuviae of previous stage. In the later stage of the insect, the insect body is

separated from the scale-like covering. The 1st instar nymph is active and mobile which locates a feeding

site before settling to feed. After settling, they begin to secrete waxy cover. The 2nd instar incorporates

the exuviae & waxy cover of 1st instar into its own scale cover adding up the material to its outer edge to

increase its diameter.

14. Cimicidae – Eg. bed bugs

The nymphal body is broad and flat without wing pads. They are mainly parasitic and obligatory

in nature, which feeds only on the blood of birds and other mammals. The adult females attach small,

elongated (1mm long) whitish eggs, in loose clusters, to surfaces where bugs hide. There are 5 nymphal

instars, each instar requiring >1 blood meal. The life-cycle is completed within 4-5 weeks @ 75-80%

RH and 83-90o F, laying 200-500 eggs during its lifetime. Mating is through Traumatic Insemination. Eg.

Cimex lectularius in temperate and subtropical and C. lotudatus in tropical Africa and Asia.

15. Reduviidae – Eg. assassin bugs

These bugs are predaceous in nature, feeding mainly on other minute insects. Some of the species

attack other organism’s habitations in search of the prey, household pests and they may often inflict

wounds on humans also. The fore legs are somewhat thickened. They eggs are oval shaped, brightly

coloured and laid on the undersurface of leaves.

16. Pentatomidae – Eg. stink bugs

The nymphal body is broad and oval shaped with the presence of more than 3 dorsal and

abdominal scent glands, 3-segmented tarsi and 5-segmented antenna. Most of the species are herbivores

and few are predators on lepidopteran larvae. The eggs are barrel shaped, variously coloured and are laid

in groups on leaves.

17. Lygaeidae – Eg. lygaeid bugs

Most of the species are destructive to crops and few spp. (eg. Geocoris sp.) are predaceous on

other injurious insects. Antennae are placed high at the head edge, around the upper half of the eye level.

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on insects like paper wasp. Many phytophagous heteropterans scavenge dead insects in their immature

stages.

18. Coreidae – Eg. coreid bugs

Coreid bugs are somewhat similar in appearance to that of lygaeids with difference in wing

pattern, colour, position of the eyes, distinctly segmented antennae. Also the eggs are oval shaped and are

laid singly on plant surface.

19. Tingidae – Eg. lace bugs

They usually feed on plants. The eggs are laid on plant surfaces in groups, elliptical in shape and

dark coloured. Tingid nymphs can be recognized with the presence of spines on the upper body surface

and the mesoleuron and metapleuron are fused together into a single piece.

20. Miridae – Eg. leaf bugs

Most of the species are plant feeders and some are predaceous on small insects. Eg. Tarnished

plant bug, Lygus oblineatus (Say). The body of nymphs is not spinous, meso and metapleuron are distinct

unlike tingid bug and elongated eggs are laid singly, attached on plant tissue. The species, Creontiades

pallidus (Rambur) can carry plant disease.

Heteropteran Aquatic Insects

1. Notonectidae – Eg. backswimmer

Backswimmers are found in pond, streams and lake margins, small pools, and intertidal marshes.

They swim on their backs and their natatorial legs aids in swimming. The front legs are adapted for

holding prey whereas the middle and hind legs are covered with long hairs, hind legs acting like an oar.

They are capable of trapping air bubble within hairs present on the body which helps in respiration

(plastron). Eggs are laid on or in plant tissues in rows and groups. They are predaceous on other insects,

snails and small fish.

2. Corixidae – Eg. water boatman

In certain ways, they mimic backswimmers such as body form, middle and hind leg structure, and

the use of a plastron for breathing and also share the same habitat type. Others include brackish mud,

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their backs and have a modified beak that is short, blunt, triangular and not clearly segmented. This

unusual beak configuration is not restricted to the intake of just juices as in most hemipterans. Oval-

shaped eggs are laid in groups and placed on nearby aquatic plants or other objects. Depending on the

organisms, these may be herbivores, detritivores, omnivores, predators, or scavengers.

3. Nepidae – Eg. water scorpions

They are either small and elongated, or wide and rectangular in shape; they breathe through a long

snorkeling or caudal cord. The legs are long and slender with a raptorial outline of forelegs while the rear

legs are adapted for walking through the vegetation and debris underwater where they hunt prey. They

are slow swimmers but inhabit marine vegetation much of the time. Nepidae eggs have respiratory horns

that serve the same function of connecting the inner layer of air to the outside atmosphere while

simultaneously restricting the area through which rapid water loss can occur.

4. Belostomatidae – Eg. giant water bugs

These can be some of the biggest aquatic insects and are slightly flattened and oval in shape. They

obtain oxygen through a pair of strap-like retractile appendages situated at the tip of the abdomen. The

fore legs are raptorial, and the hind and middle legs are fringed with swimming feathers. The large

raptorial forelegs allow belostomatids to attack prey that can be up to twenty times larger. Belostoma

males sp. Abedus, and sp. Bear (deposited and glued) eggs on their backs before they hatch. Some

species target small fish, as well as other small animals including ducklings. The Hydrometridae and

Hebridae families are more terrestrial organisms and are considered to be closely related to the shores

and surfaces of marine environments whereas the Gerridae and Veliidae families (water striders or water

treaders) are more marine and are typically found on the water surfaces. They are typically found in

intertidal or marine environments. Some Gerrid species may lack wings. Since these are not underwater

organisms, there is no need for special breathing adaptation, and they simply breathe through spirals.

Other species, especially those inhabiting rough waters, have hairs that cover their bodies to create an air

bubble that will lift them back to the surface when they are submerged. The gerrids have long legs, and

some species have fur on their legs allowing them to walk or skate on the water surface. They feed in the

water on dropped insects, or catch prey from the water bed.

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