Scarab Beetle | Gymnetis stellata (Latreille)

California Pest Rating  for
Scarab Beetle | Gymnetis stellata (Latreille)
Coleoptera: Scarabaeidae: Cetoniinae
Pest Rating: A



Initiating Event:

Gymnetis stellata is currently Q-rated.  A permanent pest rating proposal is required to support an official pest rating.

History & Status:

Background:  Gymnetis stellata is a beetle that measures approximately 20 mm in length and 13 mm in width.  It is dark and velvety with a distinctive pattern of red-orange stripes that radiate from the center of its body.  It occurs in tropical forests at low elevations (below 1600 meters above sea level).  Adults are reported to feed on fruit, including banana, lemon, and guava (Juárez and González, 2015; Maes and Orozco, 2017; Oliveros-Guzmán, 2017).  Adults of other Gymnetis species are reported to feed on fruit, leaves, and flowers; feeding damage is reported to result in the loss of fruit (García, 2005; Montero and Seta, 2015; Segarra et al., 2014).  The larvae of Gymnetis stellata feed on decomposing organic matter.  Numerous larvae, pupal cells, and adults of this species were found in an accumulation of insectivorous bat guano in an unfinished building in Tabasco, Mexico.  It is likely other types of organic matter are used for development more frequently (Sánchez Soto et al., 2017).  The larvae of other species of Gymnetis are reported to feed on decomposing organic matter, including rotting logs (Montero and Seta, 2015; Neita et al., 2006).

Worldwide Distribution:  Gymnetis stellata has been reported from Mexico, Central America (Guatemala, Nicaragua, and Panamá), and South America (Colombia and Peru) (Duque and Cabrera, 2013; Juárez and González, 2015; Maes and Orozco, 2017; Oliveros-Guzmán et al., 2017; Ríos and Gómez, 2011; Sánchez Soto et al., 2017).

Official Control: Gymnetis stellata is not known to be under official control anywhere.

California Distribution:  Gymnetis stellata is not known to be present in California.

California Interceptions:  Gymnetis stellata was found outside of a produce terminal in San Francisco County in 2007 (CDFA Pest and Damage Report Database, 2018).

The risk Gymnetis stellata would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Gymnetis stellata appears to be restricted to warmer climates. It is likely that this beetle would be limited to the southern, coastal portion of California if it became established here.  Gymnetis stellata is presumed to be capable of feeding on a wide variety of fruit (and possibly flowers as well), and the larvae are known to feed on decomposing organic matter.  Presence of adult and larval food is not expected to be a significant limiting factor of the potential distribution of this species in California.  Therefore, Gymnetis stellata receives a Medium (2) in this category.

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Gymnetis stellata apparently feeds on decomposing organic matter as a larva and a variety of fruits as an adult. Based on the known feeding habits of this species and others in the genus, it appears likely that a very wide variety of fruits could be fed upon by the adults.  Therefore, it receives a High (3) in this category.

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Reproductive and Dispersal Potential: Cetoniines are typically strong fliers.  All life stages of stellata appear unlikely to be dispersed artificially, because the larvae live in rotting organic matter and the adults are large and mobile.  Therefore, it receives a Medium (2) in this category.

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Adult Gymnetis stellata are reported to feed on fruit.  Other Gymnetis species have been reported to cause damage to fruit as a result of adult feeding.  For example, adult feeding by two species of Gymnetis has damaged peach, apricot, and tomato fruit in Argentina (Montero and Seta, 2015).  It is possible that stellata could feed on and damage a variety of fruits, especially soft-skinned ones.  Some Gymnetis species feed on other plant parts, including leaves and flowers, as well as fruit.  It is possible that G. stellata may share such broad feeding habits, and if it does, it could damage crops other than fruit.  Damage to crops could lower yield and increase production costs.  Therefore, it receives a Medium (2) in this category.

Economic Impact:  A, B

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score:  2

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: Adult Gymnetis stellata feed on fruit, and they may also be capable of feeding on other plant parts, including flowers and leaves. If this beetle became established in California, it could attack native plants, which could disrupt natural communities.  In addition, if it was a pest in agricultural situations, it could trigger treatments.  Therefore, it receives a High (3) in this category.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact:  A, D

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

 B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

Environmental Impact Score:  3

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Gymnetis stellata: Medium (12)

Add up the total score and include it here.

–Low = 5-8 points

–Medium = 9-12 points

–High = 13-15 points

6) Post Entry Distribution and Survey Information: Gymnetis stellata is not known to be present in California.  It receives a Not established (0) in this category.

–Not established (0) Pest never detected in California, or known only from incursions.

–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

–Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

–High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (12)


It is possible that the climate of California may not be conducive to the establishment of G. stellata.  It is also possible that this beetle would not have significant economic or environmental impacts even if it did become established in the state. Although adult feeding is capable of causing damage to, and loss of fruit, there appears to be little mention of Gymnetis species as significant pests in the literature.

Conclusion and Rating Justification:

Gymnetis stellata is a plant-feeding insect that has the potential to damage fruit and possibly other crops, and it could have environmental impacts as well.  It is not known to be present in California.  For these reasons, an “A” rating is justified.


CDFA Pest and Damage Report Database.  2018.  Gymnetis stellata.  Plant Health and Pest Prevention Services. CA Department of Food and Agriculture.  Accessed April 25, 2018:

Duque, M. E. T. and Cabrera, S. G.  2013.  Reporte de los fondos del MEFLG: Melolόntidos del Museo Entomolόgico Francisco Luís Gallego.  Boletin del Museo Entomolόgico Francisco Luís Gallego 5:27-56.

García, C. V.  2005.  Reconocimiento fitosanitario en cinco variedades cultivadas de macadamia (Macadamia integrifolia Maiden et Betche) en la zona cafetera colombiana.  Manejo Integrado de Plagas y Agroecología 74:69-76.

Maes, J- M. and Orozco, J.  2017.  Catalogo ilustrado de los Cetoniinae y Trichiinae (Coleoptera: Scarabaeidae) de Nicaragua.  Revista Nicaraguense de Entomologia 120:1-111.

Montero, G. A. and Seta, S. A.  2015.  Daños producidos por dos especies de Gymnetis (Cetoniinae: Scarabaeidae) en frutos de tomate, damasco y durazno en el sudeste de Santa Fe.  Agromensajes 41:18-22.

Neita, J. C., Orozco A., J., and Ratcliffe, B.  2006.  Escarabajos (Scarabaeidae: Pleurosticti) de la selva baja del bosque pluvial tropical <<BP-T>>, Chocό, Colombia.  Acta Zoológica Mexicana (n.s.) 22:1-32.

< lang="es">Oliveros-Guzmán, E., Ponce-Saavedra, J., and Niño-Maldonado, S.  2017.  Nuevos registros de Gymnetis stellata (Latreille, 1833) (Coleoptera: Scarabaeidae: Cetoniinae) para los estados de Michoacán y Tamaulipas, México.  Folia Entomológica Mexicana (nueva serie) 3:9−11.

Ríos, M. A. M. and Rojas-Gómez, C. V.  2011.  Escarabajos de mayo y mayates (Insecta: Coleoptera: Melolonthidae).  pp. 391-397 in Angón, A.C. (ed.), La Biodiversidad en Veracruz.  Volumen II.  Comisión Nacional para el Conocimiento y Uso de la Biodiversidad, Gobierno del Estado de Veracruz, Universidad Veracruzana, Instituto de Ecología, A.C. México.

Sánchez Soto, S., Jiménez, M. M., Gόmez, W. S. S., Aguilar, J. D. L., and Méndez, A. D. J.  2017.  Sitio de reproducciόn de Gymnetis stellata en Tabasco, México.  Boletín del Museo de Entomología de la Universidad del Valle 17:16-20.

Segarra, A. E., Morales-Pérez, A, Franqui, R. A., and Ratcliffe, B. C.  2014.  First report of a South American cetoniine beetle, Gymnetis strigosa (Olivier, 1789) (Coleoptera: Scarabaeidae: Cetoniinae), in Puerto Rico.  The Coleopterists Bulletin 68:217-218.

Symbiota Collections of Arthropods Network.  Accessed January 12, 2018:


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Pest Rating: A

Posted by ls