Tortoise beetles

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Common name: Tortoiseshell beetle

Scientific name: Aspidomorpha miliaris F.

Common name: Green tortoise beetle 

Scientific name: Cassida circumdata Herst 

Common Name: 13-spotted tortoiseshell beetle

Scientific Name : Laccoptera tredecimpunctata F.

Taxonomy

Class

Insecta

Order

Coleoptera

Family

Chrysomelidae

A number of species come under the common name of tortoise beetles or tortoiseshell beetles.  They are characterized by flattened, spiny larvae and adult beetles with broad domed oval shaped elytra.

Economic importance

Seldom a serious pest, but tortoise beetles can cause considerable defoliation during severe infestation.  Severe damage at the vegetative and root initiation stages may reduce storage root yield.

Geographical distribution

Throughout Africa, Southern China, Southeast Asia. At least four species of Aspidomorpha and eight other Chrysomelidae have been recorded in East Africa. Several species occur in Southeast Asia including Cassida circumdata and C. obtusata, the green tortoiseshells; A. miliaris, the spotted tortoiseshell; A. elevata, the golden tortoiseshell, and A. amabilis, with reddish brown elytra; Laccoptera tredecimpunctata and L. philippinensis, the 13-spotted and orange tortoise beetles, respectively.  In south-eastern USA, the golden tortoise beetle Charidotella bicolor is a common but minor pest.

Damage

The young larvae scrape on the surface of the leaves leaving a pale or brown translucent membrane. Older larvae produce round holes. When feeding in groups, irregular holes are formed and can totally defoliate the plant.  Adults also produce round holes in the leaves. Occasionally attacks are sufficiently severe to completely skeletonise the leaves, defoliate the plant and peel the stems.  However, usually damage does not affect yield.

Morphology

Tortoiseshell beetle (A. miliaris)

Egg  The creamy white eggs are housed in a papery golden brown ootheca of 10-25 layered membranes  filled with three eggs each . The egg is elongated measuring 1.5 to 2 mm long. The size of ootheca ranges from 8-13mm long and 8-10 cm wide.

Larva  Young larvae  (first to third instar) are light brown with 2 rows of 5 square round black spots on the thoracic area and 7 rows of 2 narrow rectangular spots black spots on the abdominal region. The  narrow rectangular spots split into two making 7 rows of 4 spots as the larva matures, and the colour of the body changes to golden brown. The body is surrounded with black spines. Mature larva measures 7-10 mm long and 3-5 mm wide.

Pupa  The pupa is yellow with darker shade along the body margin. The lateral spines of the head, thoracic and the anterior part of the abdomen are reduced. The lateral spines of the abdomen are compressed towards the posterior end .  The number of spots is reduce to one pair on the anterior most portion of the head, one on each side of the head, two pairs on the thoracic area and 4-6 spots on the posterior end. Pupa measures 10-12 mm in length and 5-7 mm in width.

Adult  The adult is a medium-sized golden tortoise beetle with broad transparent extension of the elytra, 10-13 mm long and 9-13 mm wide. The  elytra contain 4 of broad black spots on the transparent extension of the elytra and 19 -23 small spots for the female and 15-17 small spots for the male with a dark golden yellow dorso-median line.

Green tortoise beetle (C. circumdata)

Egg  The egg is elongated, 1.5 mm which is 4 times longer than its width. The light green egg is covered by translucent golden brown parchment-like membrane with two longitudinal ridges.

Larva  The larva appears green, flattened, slug-like with two pairs of branched lateral fleshy green spines per segment except on meso- and metathroax which has three pairs each. The skin from the last moult is attached to a pair of subanal spines, held upright and appears dark brown. Late instars change colour from green to yellowish green, becoming more yellow near pupation. Mature larvae reach 5.5 mm.

Pupa  The body is yellowish green, oval, flattened with prominent prothoracic shield. The head is hidden and the abdomen has a single row of whitish spines on margins. All the larval skins are attached to the posterior end appearing as an irregular black mass.

Adult  The adult is a small tortoise beetle with metallic greenish yellow body.  The wings have 3 irregular longitudinal black band with lateral extension like a shield. The middle black band on inner margin of wing shares with opposite wing. The surface is pitted.

13-spotted tortoiseshell beetle (L. tredecimpunctata)

Egg  The oval eggs measure 1 to 1.5 mm and are laid singly on the leaf surface. The newly laid egg appears yellow turning golden brown when about to hatch. The egg is covered with orange brown parchment-like membrane with a distinct flap on top.

Larva  The larva is flat, yellowish to golden brown, and possesses lateral fleshy spines. The spines are unbranched in the first instar then becoming branched in the later instars.  The exuvia after each larval moults become attached to a pair of long fleshy subanal spines appearing as a black mass of dirt and not distinct and differentiated as in Cassida circumdata. Mature larva measures 7.5 mm.

Pupa  The pupa is brownish orange. The anterior most pair of thoracic setae is branched  and the lateral fleshy setae of the abdomen is greyish and unbranched. Dark brown mass consisting  of larval exuviae are still attached to abdominal tip.

Adult  The adult is a golden brown beetle measuring 6-8 mm with 11 black spots on the elytra and 2 smaller black spots on prothorax. The prothorax is enlarged to form a shield with lace-like pattern on the surface. The mesothoracic wing is thickened with shield-like extension of the margin and showing lace-like appearance on the surface.

Biology and ecology

Tortoise beetles are widely distributed and often very common.

Tortoiseshell beetle

The ootheca are deposited singly and glued onto the surface of the leaf. The eggs hatch after 7-10 days. Newly hatched larvae feed by scraping the surface of the leaf. The insect undergoes 5 larval instars, each instar lasts 5-7 days. Earlier instars are highly gregarious and become less gregarious as they mature. Pupal period lasts for a week. Adults live up to two months.

Green tortoise beetle

The mated female lays around 250 eggs in  2 to 5 days after emergence. The eggs are laid singly on either surface of the leaf and covered with the translucent golden brown parchment-like membrane.  Hatching of eggs occurs in 4 to 7 days.  The insect undergoes 5 larval instars, each instar lasts 1 to 6 days. After each moult, the exuvium (cast skin) becomes attached to the spines and each succeeding exuvium is distinct and attached to the preceding one. These cast skins are carried by the larvae when feeding or at rest. When the larva is disturbed, it is placed over the body and is used as protective shield. The length of the accumulated exuvia becomes longer as the larva matures. The total larval development ranges from 7-26 days. The pupa becomes firmly attached with silken threads by its caudal end to either surface of the leaf. The pupal period is 4-8 days. The total life cycle ranges from 15-41 days. Longevity of adults lasts 2-29 days. The male to female ratio of adults is 1:0:1.1.

13-spotted tortoiseshell beetle

The mated female beetle starts laying eggs 3 days after emergence and lays relatively few eggs, about 7 eggs. The eggs are laid singly in batches of 3 eggs per group. The incubation period lasts 5 to 6 days. There are 5 larva instars, each instar lasts 1-8 days with a total larval period of 7-30 days. The larva is sluggish and rarely moved from its feeding site unless disturbed or when changing feeding area.  The larva carries the attached exuviae in an upright position concealing the larvae when at rest. When about to pupate the larva attaches itself firmly on the underside of the leaf. The pupa still carries the exuviae attached to the subanal spines. Pupal period ranges from 3-10 days. The total life cycle is 14-46 days. Longevity of adults lasts up to 2 weeks. Male to female ratio is 1.9:1.0.

Host range

Sweetpotato is the main host, while other Convolvulaceae especially Ipomoea triloba are alternative hosts. Other crops which have been established as alternative hosts are coffee, beet, potato and various flowers.

Detection and inspection

Tortoise beetle damage is quite conspicuous, as are the adults and immatures themselves.

Management

Control of these pests is seldom necessary.

Cultural control

Removal of convolvulaceous weeds in the surrounding area may reduce their numbers.

Biological control

Several natural enemies including egg and larval parasites (Tetrastichus sp., Eulophidae;Chalcidae) and predators (Stalilia sp., Mantidae) have been reported in Southeast Asia.

References

Amalin, D.M. and E. A. Vasquez. 1993. A handbook on Philippine sweet potato pests and their natural enemies. International Potato Center (CIP), Los Baņos, Philippines. 82 p.

Ames, T., Smit, N.E.J.M., Braun, A.R., O'Sullivan, J.N., Skoglund, L.G. 1997. Sweetpotato: Major pests, diseases, and nutritional disorders. International Potato Center (CIP), Lima, Peru, 152 p.

Capinera, J.L. 2004. Golden Tortoise Beetle.  Featured Creatures Factsheet EENY-014, Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. http://edis.ifas.ufl.edu/IN140

Oudhia, P. and J. Ganguli, J. 1999. Outbreak of Tortoise beetle Aspidomorpha miliaris F. (Coleoptera ; Chrysomelidae) in Chhattisgarh plains. Insect Environment 5(3) : 110-111.

Shepard, B.M. G.R. Carner, A.T. Barrion, P.A.C. Ooi and H. van den Berg. 1999. Insects and their Natural Enemies Associated with vegetables and Soybean in Southeast Asia. Quality Printing Co. SC. USA. 108 pp.

Hill, D.S., 1983. Agricultural insect pests of the tropics and their control - 2nd ed. Cambridge University Press, Cambridge, 45 p.

Vasquez, E.A. and C. E. Sajise. 1989. Pests of sweet potato: Insects, mites and diseases.  PRIS and PRCRTC, Visayas State College of Agriculture, Baybay, Leyte, Philippines. 66 pp.

Vasquez, E. A. 2002. Biology of Tortoiseshell beetle, Aspidomorpha miliaris (F.), Chrysomelidae. Unpublished report. PhilRootcrops, Leyte State University, Baybay, Philippines.

Contributed by: Erlinda Vasquez and Vilma Amante

Taxonomy

Economic importance

Geographical distribution

Damage

Morphology

Biology and ecology

Detection and inspection

Host range

Management

References

Damage caused by adult tortoise beetles (E. Vasquez). 

 

An empty egg case (ootheca) and young larvae of tortoiseshell beetle, and grazing damage by the larvae resulting in papery translucent patches on the leaf (E. Vasquez).

 

Older larvae of  tortoiseshell  beetle feeding on leaves (E. Vasquez).

Tortoiseshell beetle pupae are sedentary on the leaf surface (E. Vasquez).

Green tortoise beetle larva (left) showing the previously-shed skin attached and held upright.  Adult (right) and feeding hole (E. Vasquez).

 Adult 13-spotted tortoiseshell beelte and round feeding holes on leaf (E. Vasquez).

Orange tortoise beetle adult (E. Vasquez).

Golden tortoiseshell beetle larva (left) and adult (right) (A. Braun).

Golden tortoise beetle and feeding holes (P. Choate, UF)