This nicely colored insect are abundant in the garden. It is the commonly found Green shield bug (Palomena prasina) ^{[Aukema et al. 2016]}.

The animal is green in the summer and changes to a brown color in the autumn.

1. DISTRIBUTION

The Green shield bug is one of the most common large true bugs in the Netherlands. In the garden they are represented every year as well in larger numbers.

2. BEHAVIOUR

2.1. ACTIVITY

The bug is active between March and November and has a peak between Juli and September. Nymphs appear in June. The adults overwinter ^{[Schuh 2018]}.

2.2. DEVELOPMENT

True bugs are hemimetabolous, which means that they develop by moulting a number of times towards adulthood. With each molt they change a little bit towards the final adult stage, which is contrast with holometabolous insects that will undergo a complete metamorphosis, like a butterfly.

P. prasina has one generation per year, and ovipositioning occurs between spring and Juli ^{[Schuh 2018]}. In 5 moults, instars, adulthood is achieved ^{[Tuncer et al. 2015]}.
Eggs are laid in clusters on plant stems and hatch after about 5,5 – 12 days, in a period of 0 – 4 days, depending on temperature ^{[Saruhan et al. 2010]}.

Temperature influences the development speed of instars (in the referenced research it varied between 16 – 28°C) ^{[Saruhan et al. 2010]}:

1^st intar: ±4 – 8,6 days
2^nd intar: ±7,5 – 20 days
3^rd intar: ±7,5 – 20 days
4^th intar: ±6,5 – 17,8 days
5^th intar: ±8 – 23 days

As the species can only overwinter as adult, the nymphs undergo growth acceleration as the day length becomes shorter ^{[Saulich & Musolin 2014]}. The new adult generation appears mid to late Juli ^{[Schuh 2018]}.

Aggregation

The first instars of shield bugs aggregate in a group after hatching. The reason for this behaviour is that it increases their survivability. First instars do not eat and only consume moisture ^{[Lockwood & Story 1986]}. Research has shown the following advantages of aggregation ^{[Lockwood & Story 1986]}:

1. Protection against dehydration
   The nymphs in an aggregation are better protected against dehydration as the air pockets that occur between the aggregation members contains moisture which remains than accessible to the nymphs. Individuals that are alone do not have this
2. Temperature regulation
   Aggregation provides a slightly lower mortality rate at higher temperatures.
3. Increased development speed
   The development speed of the nymphs in the aggregation at higher humidities, is higher than of those that are alone. This benefit exists up to a temperature of 31°C. The aggregation is capable of temperature regulation and positively influences the growth speed.
4. Increased adherence to the substrate
   Aggregation increases adherence to the plant surface and prevents nymphs from falling from the plant. The effect becomes lower as the aggregation increases in size because at a threshold of 11-15 nymphs the individuals start to stack in layers and hold each other instead of the plant.
5. Increased protection against predators
   The aggregation offers protection against certain predators:
   • Hempitera: less individuals are eaten with the lowest amount in aggregations of 3 nymphs and the most in aggregations of 15
   • Ants: least casualties in aggregations of 10 to 15 nymphs, and the most in aggregation of five or less
   • Against wasps aggregation does not seem to offer protection

Aggregation is controlled by pheromones as described in paragraph 3.4.

2.3. FOOD

De nymphs are polyphagous on different plants and trees and coprophagous on bird dropping, as shown by some remarkable observations.
The first instar nymphs don’t eat and only consume moisture ^{[Lockwood & Story 1986]}. The second instar feeds on herbs ^{[Tuncer et al. 2015]}. The other stages feed especially on fruit ^{[Tuncer et al. 2015]}.

Bird droppings

This as well as other true bug species feed on the white part of fresh bird droppings ^{[Ramsay 2013]}, which consists almost entirely of uric acid and is rich in nitrogen. It’s the fifth instars that show this behaviour.

Pest

The species is a pest on a number of commercially cultivated plants ^{[Tuncer et al. 2015],[Alford 2014]}:

• Hazel
• Apple
• Pear
• Raspberry

In Turkey the species is a major pest on hazel and the damage caused by the insect is characterized by ^{[Tuncer et al. 2015]}:

1. Premature dropping of nuts
   nuts are light colored and shrunken on the bottom
2. Spots and damage to the kernel
3. Shrunken kernels
   (note: the quoted article indicates that this damage cannot be addressed unambiguously to bus damage)

On raspberry the bug damage gives the fruit an  unpleasant taste ^{[Alford 2014]}.

On apple and pear the damage causes spots and dents in the fruit surface ^{[Alford 2014]}.

3. COMMUNICATION

In shield bugs communication between the sexes occurs in two phases ^{[Virant-Doberlet & Cokl 2004],[Drosopoulos & Claridge 2006],[Borges et al. 1987]}:

1. Using pheromones the insect is brought to the proper plant
2. Using song the insect is guided to the partner

3.1. SEX PHEROMONES (long distance)

The male secretes a species specific volatile pheromone to guide the female towards him. She detects the pheromone using her antennae that she will hold in a ‘V’ shape in the direction of the source, which enables her to find the proper plant where the male resides ^{[Borges et al. 1987]}.

The pheromones are produced in glands in the thorax of the adult animals ^{[Millar 2005]}.

3.2. SONG (short distance)

Like many other insect families true bugs produce songs for:

• attraction / repulsion (repulsion only by the female)
• mating

After the female has arrived on the plant where the male resides she will produce, stimulated by pheromones, a calling song that is followed by the male while producing the its own answer song and excreting pheromones ^{[10],[Drosopoulos & Claridge 2006]}.

The songs are produced by the tergites in the abdomen ^{[Čokl 2008]}. The instrument consists of tergites I and II and is vibrated using muscles ^{[Čokl 2008]}.
The song is soft but is amplified by the plants on which the bug resides. The vibrations from the tergites spread through the body and the legs into the branch and can extend tens of centimeters through it.

The bugs have a number of vibration receptors in their legs to listen to vibrations ^{[Čokl 2008]}. Using time difference in the arrival of the vibration waves between the spread out legs, the bug can determine the direction of the source. The bug will stop at branches to listen in order to take the proper exit or direction. In this way the male can accurately track the sending female.

Each species has it own preference in plant. P. prasina has specialized in woody plants and produces frequencies that are best amplified for those types of plants ^{[Polajnar et al. 2013]}. The species is capable of adapting the frequency based on the substrate it is standing on ^{[Polajnar et al. 2013]}. 
The song uses tones between 70 – 150 Hz with peaks towards 900Hz.

Lilac

The adult insects emerge everywhere but especially in Lilac (Syringa vulgaris).

When pruning the dried flowers they often contain bugs, sometimes in pairs. The relation to the plant is described in one observation (Assmann, 1854, als Pentatoma dissimile) ^{[Assmann 1854]}. 
Possibly it is related to larvae as one research article mentions feeding the larvae leaves of this plant ^{[Musolin & Saulich 1997]} and another reference mentions the it as a food plant for other species of shield bugs ^{[Beeles 2019]}.
I suspect it has to do with mating and the fact that Lilac is a woody plant that works well in communication between the sexes. This would explain the relatively high number of pairs I find in the plant.

3.3. TOUCH

When the sexes finally meet they will touch each other using their antennae. The bugs will turn around each other and the male encourages the female by pushing her behind up with his head. When the female accepts the male during this process she will point her abdomen in the air and the male will move against her in reverse.
If she does not accept the male during this process she will repel him using pheromones ^{[Borges et al. 1987]}.

3.4. AGGREGATION PHEROMONES

Aggregating first instar nymphs communicate using pheromones to keep the group together or disperse in case of imminent danger ^{[Borges et al. 1987]}.

Nymphs produce pheromones in glands in the abdomen ^{[Millar 2005]}.

3.5. DEFENCE AND OFFENCE

The bugs use pheromones with the purpose to ^{[Lockwood & Story 1986]}:

1. Distract the predator
   Pheromones contain components that occur in the alarm pheromones of their attackers, which confuses them.
2. Repel / intoxicate their attacker
   Some components are very distasteful or even lethal to their enemies.

4. IDENTIFICATION

4.1. EGGS

The eggs of the Green shieldbug are bright grass green in color and become gradually more green-yellow as the nymphs inside them develop. They are clearly barrel shaped with a round lid on top.

The eggshell is thin so developed nymphs become visible through it.

4.2. INSTARS

1^st INSTAR

When emerging from the eggs the first instars are light yellow-green in color with transparent white legs. They change color as they harden and adopt a dark red-brown scheme color with pink-orange spots or a black scheme with light green spots.

2^nd INSTAR

The second instar is black with a light green abdomen with whitish and black spots on the back and lower edge.

3^rd INSTAR

4^th INSTAR

The fourth instar has a flatter and rounded shape and is either complete green in colour covered with small black dots or green with a black thorax similar to the second instar but bigger in size.

5^th INSTAR

4.3. ADULTS

Adults change color depending on the seasons, a phenomenon called seasonal polyphenism. The new generation is green and colors brown towards the autumn. In spring the brown color is replaced by green again ^{[Schuh 2018]}, a more darker green than the summer generation ^{[Saruhan & Tuncer 2006]}.

The adults are identifiable using the following characteristics:

1. Evenly green or brown color
2. Dark wing membranes
3. Shield without a light base point
4. Antennae segments II and III almost equal in length
5. Antennae segments IV and V partly red colored (clearly visible in summer dress)
6. Front neck shield slightly hollow

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Literature

^{Alford 2014} Alford, D., 2014. Pests of Fruit Crops. Boca Raton: CRC Press, https://doi.org/10.1201/b17030

^{Assmann 1854} Assmann A., 1854. Hemiptera., Verscheichnis der bisher in Schlesiën aufgefundenen wanzartigen Insekten, Hemiptera Linné, Zeitschrift für Entomologie 8:1-106

^{Aukema et al. 2016} Aukema, B., Heijerman Th. & Kalkman V.J., 2016. Veldgids wantsen deel 1. – EIS Kennis­ centrum Insecten, Leiden.

^{Beeles 2019} Beeles L., 2019. Stink Bugs of Oregon, Oregon Department of Agriculture Insect Pest Prevention & Management Program.

^{Borges et al. 1987} Borges, M., Jepson, P. C., & Howse, P. E., 1987. Long‐range mate location and close‐range courtship behaviour of the green stink bug, Nezara viridula and its mediation by sex pheromones. Entomologia experimentalis et applicata, 44(3), 205-212.

^{Čokl 2008} Čokl, A., 2008. Stink bug interaction with host plants during communication. Journal of Insect Physiology, 54(7), 1113-1124.

^{Drosopoulos & Claridge 2006} Drosopoulos, S., & Claridge, M. F., 2006. Insect sounds and communication: physiology, behaviour, ecology, and evolution (No. 21784). CRC Press; Taylor & Francis.

^{Lockwood & Story 1986} Lockwood, J. A., & Story, R. N., 1986. Adaptive functions of nymphal aggregation in the southern green stink bug, Nezara viridula (L.)(Hemiptera: Pentatomidae). Environmental Entomology, 15(3), 739-749.

^{Millar 2005} Millar, J. G., 2005. Pheromones of true bugs. The Chemistry of Pheromones and Other Semiochemicals II: -/-, 37-84.

^{Musolin & Saulich 1997} Musolin, D. L., & Saulich, A. K., 1997. Photoperiodic control of nymphal growth in true bugs (Heteroptera). Entomological Review, 77(6), 768-780.

^{Polajnar et al. 2013} Polajnar, J., Kavčič, A., Kosi, A., & Čokl, A., 2013. Palomena prasina (Hemiptera: Pentatomidae) vibratory signals and their tuning with plant substrates. Open Life Sciences, 8(7), 670-680.

^{Ramsay 2013} Ramsay, A. J., 2013. Coprophagous feeding behaviour by two species of nymphal pentatomid. British Journal of Entomology and Natural History, 26, 145-147.

^{Saruhan et al. 2010} Saruhan, I., Tuncer, C., & Akça, İ., 2010. Development of green shield bug (Palomena prasina L., Heteroptera: Pentatomidae) in different temperatures.

^{Saruhan & Tuncer 2006} Saruhan, İ., & Tuncer, C., 2006. Palomena prasina L.(Heteroptera: Pentatomidae)'nın bazı morfolojik ve biyolojik özelliklerinin saptanması üzerinde araştırmalar.

^{Saulich & Musolin 2014} Saulich, A. K., & Musolin, D. L., 2014. Seasonal cycles in stink bugs (Heteroptera, Pentatomidae) from the temperate zone: diversity and control. Entomological Review, 94, 785-814.

^{Schuh 2018} Schuh R.T., 2018. Invasive Stink Bugs and Related Species (Pentatomoidea): Biology, Higher Systematics, Semiochemistry, and Management, American Entomologist, Volume 64, Issue 3, Fall 2018, Pages 197–198, https://doi.org/10.1093/ae/tmy050

^{Tuncer et al. 2015} Tuncer C., Saruhan I. & Akça I., 2015. "TRUE BUGS PROBLEM IN TURKISH HAZELNUT ORCHARDS", Ondokuz Mayis University, Faculty of Agriculture Department of Plant Protection, SAMSUN TURKEY, 2015

^{Virant-Doberlet & Cokl 2004} Virant-Doberlet, M., & Cokl, A., 2004. Vibrational communication in insects. Neotropical Entomology, 33, 121-134.

Citation

Krischan, O.R., 2025. Palomena prasina. Kerfdier, www.kerfdier.nl. Accessed on 30 April 2025.

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