Where do an adult shield bug’s scent glands open?

Between the middle and hind legs

What is the best clue for telling it from the scarce tortoise bug?

A slight dip at the front of the head

Tortoise Bug

Eurygaster testudinaria

The tortoise bug (Eurygaster testudinaria) is a 9–11 mm shield-backed bug (family Scutelleridae) found from Portugal and Britain across Europe and Asia to Japan. A huge plate called the scutellum covers almost its whole back, like a tortoise shell. It sucks sap from grasses, sedges and rushes in damp and dry grassland, and spends the winter as an adult in dry leaf litter.

Also known as Tortoise shieldbug, Schildkrötenwanze (German: “tortoise bug”), Gewone pantserwants (Dutch: “common armour bug”)

Tortoise bug abilities

Whole back under one shieldStill debated
A giant scutellum covers its abdomen and folded wings in one smooth, rounded shield.
- Shield-backed bugs are named after this greatly enlarged scutellum. Their colourful tropical cousins are called jewel bugs.
- In the green shieldbug, from a different family, the dark tips of the wings show behind the scutellum.
- How much the shield protects it from birds or spiders has not been tested, so treat “armour” as an idea, not a measured fact.
Body length
Tortoise bug9–11 mm
Scarce tortoise bug8.5–10 mm
Sunn pest≈12 mm
Green shieldbug12–13.5 mm
Bars show the middle of each range.
Sources [1, 2, 3, 4, 5, 13, 15]
3 plant families on the menu
It pushes its beak into grass, sedge and rush stems and sucks up the sap.
- Main foods: grasses (Poaceae), sedges and their kin (Cyperaceae, such as cotton-grasses, Carex and clubrushes) and rushes (Juncaceae).
- Older nymphs and adults sometimes feed on plants of the daisy and carrot families too.
- All shield-backed bugs eat plants; none hunt other animals.
Sources [1, 6, 7, 16]
2 sets of scent glands in one life
Like other true bugs, it carries scent glands that release a strong-smelling defence.
- Nymphs have scent glands on top of the abdomen. Adults use glands in the thorax that open between the middle and hind legs.
- In its close relative Eurygaster maura, the adult scent contains (E)-2-hexenal and (E)-2-hexenyl acetate, which scientists call a typical shield-backed bug mix. The tortoise bug’s own scent has not been analysed.
- In an African shield-backed bug, the nymph glands switch off at the final moult and the adult glands take over.
- Bugs in the shield bug group have had scent glands for at least 165 million years.
Sources [9, 10, 17]
14 eggs per batch (sunn pest)
Tortoise bug relatives lay their eggs in tidy batches on plants: in the sunn pest, 2 rows of 7.
- A sunn pest female usually lays 28–42 eggs in 2–3 batches, on the undersides of leaves, on stems or on weeds. The eggs hatch in 6–28 days.
- Detailed egg counts for the tortoise bug itself are not in the sources we could read.
- Some tropical shield-backed bugs, like Pachycoris stallii in Mexico, guard their eggs and young nymphs.
- Egg-parasitoid wasps attack Eurygaster egg masses. In one Iraqi study, 32–55% were parasitised in April.
Sources [13, 14, 18]
5 nymph stages (sunn pest)
Nymphs grow by moulting their skin, and only the last moult gives them working wings.
- Tortoise bug nymphs feed on grasses from May to August, and new adults appear from July.
- In the sunn pest there are 5 nymph stages over 20–45 days. Wing buds show in stage 4 (front wings) and stage 5 (hind wings).
- The openings of the adult scent glands form quickly, during the final moult.
- Across shield bugs, nymph colours often differ from adult colours.
Sources [4, 6, 9, 13, 19]
Adult the stage that survives winter
Adults spend the winter resting in dry leaf litter, sometimes in small groups, and wake in spring.
- In Britain adults are seen all year, with peaks in spring and autumn either side of winter.
- They winter in dry ground litter, often in drier places than where they feed in summer.
- The sunn pest becomes active when the leaf litter warms to about 12–13 °C.
- In a field test in Iraq, 66–77% of wintering adults were still alive at the end of January.
Sources [4, 6, 7, 12, 13, 20]
5 colour formsStill debated
Tortoise bugs come in pale brown, brown, grey, red or blackish, with faint to bold streaks.
- Brown is the commonest colour. The pale and dark streaks across the back range from almost invisible to strongly contrasting.
- Colour cannot tell it apart from the scarce tortoise bug, which varies in the same way.
- Its browns match dry grass and litter, but no study we found has tested whether this works as camouflage.
Sources [2, 4, 5, 7]
12–14 °C when sunn pests start flying
Its wings stay folded under the shield until it is warm enough to fly.
- In shield-backed bugs the scutellum covers the wings, so they only show at take-off.
- The sunn pest flies into the fields once the average daily temperature reaches 12–14 °C, and later flies back to woods to spend the winter.
- In Britain the tortoise bug used to be uncommon but is now widespread in the south and is spreading northwards.
Sources [2, 3, 4, 13]

Tap a pin on the model or a part below.

Whole back covered by the scutellum
- The big shield is the scutellum. In shield-backed bugs (Scutelleridae) it is greatly enlarged and gives the family its name.
- It covers the whole abdomen and the folded wings, so from above the bug looks like a tiny tortoise.
- Just in front of it, the back corners of the pronotum (the “shoulders”) stick out a little more than in its look-alike, the scarce tortoise bug.
Sources [1, 2, 3, 4]
A tiny dip at the front of the head
- The best field clue: a slight central dip at the front of the head. The scarce tortoise bug (Eurygaster maura) has a smoothly rounded head.
- The dip forms because the middle lobe (the tylus) sits a little lower than the cheek plates on either side.
- Even experts sometimes need to check the genitals under a microscope to be sure.
Sources [4, 5, 6]
1.5× segment 2 vs segment 3
- The second antenna segment is only about 1.5 times as long as the third.
- In the scarce tortoise bug it is about twice as long, another clue for telling the two apart.
Sources [2, 6]
Sap plant juices only
- Like all shield-backed bugs it is a plant-feeder, piercing plants and sucking their juices through a beak.
- It sips from grasses, sedges and rushes. Older nymphs and adults also visit plants of the daisy and carrot families.
- Its relative the sunn pest injects enzymes into wheat grains while it feeds, and these break down the gluten in flour.
Sources [1, 6, 7, 8]
165 million yrs oldest fossil scent glands in its bug group
- Adult true bugs have scent glands in the thorax. Nymphs use different glands on the top of the abdomen.
- In its close relative Eurygaster maura, the adult gland is a reservoir with 2 side glands. It opens between the middle and hind legs onto rough “evaporation areas”.
- Fossils show that bugs in the shield bug group already had scent glands in the Jurassic, about 165 million years ago.
Sources [9, 10]
4 vs 2 spines in the male’s genitals
- Under the shield, the male’s genitals carry 4 small inner spines; the scarce tortoise bug has 2.
- Females have a small gap between the genital plates and the segment in front, which the look-alike lacks.
- Their DNA barcodes are so similar that the tortoise bug and the scarce tortoise bug cannot be told apart by that method.
Sources [5, 6, 11]
3 main plant families
- Grasses, sedges (such as cotton-grasses, Carex sedges and clubrushes) and rushes.
- It likes damp, open to half-shaded places such as tall sedge beds and bogs, and even salty ground.
- In Britain it was once mostly a bug of damp grassland, but it now turns up in dry grassland too.
Sources [4, 6, 7, 12]
2 rows of 7 egg batch of the sunn pest
- We found no detailed egg counts for the tortoise bug itself. Its relative the sunn pest lays neat batches of 14 eggs, 2 rows of 7, on leaves and stems.
- Tiny wasps lay their own eggs inside shield bug eggs. In Iraq, the wasp Ooencyrtus telenomicida parasitised 32–55% of the eggs of wheat-field Eurygaster in April.
Sources [13, 14]

Real tortoise bugs

Photos from Wikimedia Commons. Some of them can repaint the 3D model.

BrownThe commonest colour: brown with paler and darker streaks that can be faint or bold.Most tortoise bugs you will meetA brown tortoise bug, the commonest colour. Photo: Kulac (de.wikipedia), CC BY-SA 2.0 de
From above: the scutellum covers almost the whole back. Namur, BelgiumPhoto: Gilles San Martin, CC BY-SA 4.0
Reddish brownSome tortoise bugs are red-brown or reddish. Others are grey, pale brown or almost black.One of several colour formsA reddish-brown tortoise bug. Photo: Gilles San Martin, CC BY-SA 4.0
In a bog in Dzūkija National Park, Lithuania: damp ground suits itPhoto: Darius Baužys, CC BY-SA 3.0
NymphYoung tortoise bugs have no working wings yet. They feed on grasses from May to August and become adults from July.Wing buds appear in the last nymph stages (sunn pest)A mid-stage nymph, Worcestershire, England. Photo: gailhampshire, CC BY 2.0
A mating pair, Ermingen, GermanyPhoto: Holger Krisp, CC BY 3.0
An adult on the Vlasina Lake plateau, SerbiaPhoto: Slobodan Stevčić, CC BY-SA 4.0
An adult among green plants, FrancePhoto: Jean.claude, CC BY-SA 3.0
Sunn pest (relative)Eurygaster integriceps: about 12 mm, usually light brown, with the same giant shield.A major pest of wheat and barleyIts relative the sunn pest, a major wheat pest, in Israel. Photo: Chaym Turak, CC BY-SA 4.0
Sunn pest (relative)Eurygaster integriceps: about 12 mm, usually light brown, with the same giant shield.A major pest of wheat and barleySunn pest from above; each paper square is 5 mm. Photo: DmitTrix, CC BY 4.0

Tortoise bug by the numbers

Measured by entomologists and recording schemes. Where only its relative the sunn pest has been measured, we say so.

Length: 9–11 mm; adults; one Polish account gives 7–11 mm⁠[4, 6, 2, 7, 13]; Tortoise bug (9–11 mm)10 mmSunn pest (≈12 mm)12 mm
Colour forms: 5; pale brown, brown, grey, red or blackish; brown is commonest⁠[7, 2]
Main food plants: 3 families; grasses, sedges and rushes⁠[6, 7]
Range: Portugal → Japan; also Morocco and Tunisia; north to southern Scandinavia⁠[7, 6, 16]
Generations: 1 a year; nymphs in summer, new adults from July, adults overwinter⁠[4, 12]
Nymph season: May–Aug; nymphs feed on grasses⁠[4, 6]
Winter stage: Adult; in dry ground litter, sometimes in small groups⁠[12, 6]
Nymph stages: 5; measured in the sunn pest: 20–45 days in all⁠[13]
Eggs per batch: 14; 2 rows of 7, measured in the sunn pest⁠[13]
Tortoise bugs in Britain: 2; plus a third species, regionally extinct since 1885⁠[12]

Tortoise bug myths and facts

Tap Myth or Fact for each claim, then check the answer.

0 of 8 answered

“A tortoise bug is a kind of beetle.”
“The tortoise bug’s “shell” is made of its wings.”
“Tortoise bugs can make a stink.”
“Tortoise bugs spend the winter as adults.”
“You can tell a tortoise bug from its look-alike by its colour.”
“Tortoise bugs only live in damp places.”
“Tortoise bugs are serious wheat pests.”
“A small bug can spoil bread.”

Tortoise bug records

Superlatives for the tortoise bug and its relatives, each checked against its source.

Biggest back-plate
Whole abdomen
Shield-backed bugs (Scutelleridae)
their greatly enlarged scutellum covers the abdomen and wings⁠[1, 2]
Hardest twins to tell apart
Same barcode
Tortoise bug and scarce tortoise bug
almost indiscernible by shape, and their DNA barcodes do not separate them⁠[11]
Worst wheat bug of its region
50–90%
Sunn pest (Eurygaster integriceps)
estimated wheat yield losses in West and Central Asia and Eastern Europe⁠[21, 22]
Costliest bug control
$42 million+
Sunn pest
spent on its control in West Asia⁠[21]
Oldest bug stink
165 million years
Scent glands of shield bugs and their kin (Pentatomomorpha)
earliest fossil evidence, from the Jurassic⁠[9]

A year in the life of a tortoise bug

One generation a year: adults sleep through winter, nymphs grow up in summer.

Winter
Resting in the litter
Adults rest in dry ground litter, sometimes in small groups, often in drier spots than their summer home.⁠[6, 7, 12]
Early spring
Warming up
Adults become active again as the ground warms. In the sunn pest, this starts when leaf litter reaches about 12–13 °C.⁠[12, 13]
Spring
First adult peak
Adults are most often seen in spring. In the sunn pest, spring is the time for breeding.⁠[12, 25]
Late spring
Eggs on the plants
Relatives such as the sunn pest lay batches of 14 eggs, 2 rows of 7, on leaves and stems. They hatch in 6–28 days.⁠[13]
May–August
Nymphs feeding
Nymphs suck sap from grasses and moult as they grow.⁠[4, 6]
From July
New adults
The last moult brings the full shield and working wings.⁠[4, 6]
Autumn
Second peak, then shelter
Adults peak again in autumn before settling into their winter shelters.⁠[12]

Tortoise bug vs green shieldbug vs sunn pest

Two tortoise-shaped Eurygaster cousins and a familiar garden shieldbug from another family.

Tortoise bug vs green shieldbug vs sunn pest
	Tortoise bug	Green shieldbug	Sunn pest
Scientific name⁠[26, 15, 13]	Eurygaster testudinaria	Palomena prasina	Eurygaster integriceps
Family⁠[26, 15, 25]	Scutelleridae (shield-backed bugs)	Pentatomidae	Scutelleridae (shield-backed bugs)
Length⁠[4, 15, 13]	9–11 mm	12–13.5 mm	≈12 mm
Colour⁠[7, 15, 13]	Brown, grey, reddish, pale or blackish	Bright green, bronze-brown before winter	Variable, usually light brown
Food⁠[6, 15, 13]	Grasses, sedges, rushes	Many deciduous trees and shrubs (nymphs)	Wheat, also barley and oats
Winter⁠[12, 15, 13]	Adult in dry litter	Adult, hibernating	Adult in leaf litter in woods
Generations a year⁠[4, 15, 25]	1	1	1
Wings⁠[2, 15, 3]	Hidden under a giant scutellum	Dark wing tips show behind the shield	Hidden under a giant scutellum
Wheat pest?⁠[14, 22, 15, 21]	Disputed: only some reports from Iraq	No: it feeds on trees and shrubs	Yes, a major one

Tortoise bugs and sunn pests are so alike that experts sometimes need a microscope or DNA to tell Eurygaster species apart.

Is the tortoise bug endangered?

No. It is common in much of Europe, and in Britain it is spreading.

IUCN Red List

Not Evaluated (NE)

Trend unknown

It is common in Poland and widespread in central Europe. In Britain it was once uncommon, but it is now widespread in the south and expanding northwards.⁠[27, 12, 7, 6, 4]

Not assessed by the IUCN (Great Britain: Least Concern)

Threats

Natural enemies32–55%
Parasitic tachinid flies (Clytiomya continua and Gymnosoma nitens) attack tortoise bugs, and tiny wasps lay eggs inside Eurygaster eggs: in one Iraqi study, 32–55% of eggs were parasitised in April.⁠[7, 14]
Mistaken identity
Tortoise bugs look almost the same as wheat-pest relatives. Experts warn that identification mistakes give plant protection services wrong information.⁠[22, 11]

What’s helping

Spreading north
Once uncommon in Britain, it is now widespread in southern Britain and Ireland and is expanding its range northwards.⁠[4]
Volunteer recording
Records sent to the Terrestrial Heteroptera Recording Scheme feed the British atlas of shieldbugs.⁠[12]
Smarter pest control
For the sunn pest, scientists measure nymph numbers and egg parasitism by wasps to target control where it is really needed.⁠[28]

Relatives

Scarce tortoise bug (Eurygaster maura)Not Evaluated
Nationally Scarce in Britain, mostly on chalk and other lime-rich grassland in southern England.⁠[12, 5]
Eurygaster austriacaNot Evaluated
Regionally extinct in Britain: it lived on the Kent coast but has not been recorded there since 1885.⁠[12]
Sunn pest (Eurygaster integriceps)Not Evaluated
Far from rare: it is the most important wheat pest in Russia and a major pest from North Africa to the Middle East and Eastern Europe.⁠[22, 8]

Tortoise bug quiz

12 questions. Every answer is somewhere on this page.

Question 1 of 12Score 0

What is the tortoise bug’s big shield called?

Tortoise Bug field notes

Diet, food web, safety and badges from the Snappit field guide.

Diet & Feeding

These tiny bugs drink sap from grasses, sedges and rushes.

Primary Foods

Grasses (Poaceae)
Sedges (Cyperaceae)
Rushes (Juncaceae)
Foraging Method: Foraging

Ecological connections

GrassesDepends on
Adults and nymphs feed on the sap of grasses.
SedgesDepends on
They pierce sedge stems and sip the sap.
Tachinid fliesParasite
These parasitic flies attack Tortoise Bugs.

Safety

Danger 1/5 · Very low

It's best to observe Tortoise Bugs from a distance and not touch them.

Traits

Collections

Insects

Classification

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hemiptera
Family: Scutelleridae
Genus: Eurygaster

Also known as

Tortoise shieldbug · Schildkrötenwanze (German: “tortoise bug”) · Gewone pantserwants (Dutch: “common armour bug”) · Starrbärfis (Swedish: “sedge shieldbug”)

Sources for these tortoise bug facts

28 studies and references · checked Oct 16, 2026

Frequently Asked Questions

How to identify Tortoise Bug?

Look for six legs, antennae, three body sections and the shape of the wings. Beetles have hardened front wings; flies have just one working pair. Tiny insects may need a close view before their group is clear. Insect Identifier: upload a photo and compare the visible details.

What is Tortoise Bug's wingspan?

15-25 mm

How big is Tortoise Bug?

7-11 mm

How long does Tortoise Bug live?

180-300 days

What does Tortoise Bug eat?

These tiny bugs drink sap from grasses, sedges and rushes.

Where is Tortoise Bug usually found?

Damp and dry grassland

How many legs does Tortoise Bug have?

What is a tortoise bug?

The tortoise bug (Eurygaster testudinaria) is a 9–11 mm shield-backed bug of grassland in Europe and Asia. Its huge scutellum covers its back like a tortoise shell, and it sucks sap from grasses, sedges and rushes.

Is a tortoise bug a beetle?

No. It is a true bug, with a beak for sucking plant sap. Its shield is an enlarged scutellum, not a beetle’s wing cases, and its wings are folded underneath.

Are tortoise bugs harmful to people?

Tortoise bugs feed only on plant sap. Like other true bugs they can release a defensive smell, so it is best to watch them rather than pick them up, and to wash your hands if you do touch one.

What do tortoise bugs eat?

Sap from grasses, sedges (such as cotton-grasses and Carex) and rushes. Older nymphs and adults sometimes feed on plants of the daisy and carrot families too.

Are tortoise bugs crop pests?

Not in Europe, where they live on wild grasses, sedges and rushes. Their relative the sunn pest is a major wheat pest. Some studies in Iraq name wheat-field bugs as tortoise bugs, but these species are often confused.

How can you tell a tortoise bug from the scarce tortoise bug?

Look at the front of the head: the tortoise bug has a slight central dip, while the scarce tortoise bug’s head is smoothly rounded. The tortoise bug is also slightly larger. Colour does not help, and sometimes only a microscope can tell.

Where do tortoise bugs go in winter?

Adults spend the winter in dry ground litter, sometimes in small groups. They become active again in spring, and new adults appear from July.

What is the sunn pest?

The sunn pest (Eurygaster integriceps) is a 12 mm relative of the tortoise bug. It feeds on wheat and barley from North Africa to Central Asia, and the enzymes it injects into grain break down the gluten in flour.

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