''Zygogramma bicolorata'', variously referred to as the Parthenium beetle or Mexican beetle, is a species of

leaf beetle The insects of the beetle family Chrysomelidae are commonly known as leaf beetles, and include over 37,000 (and probably at least 50,000) species in more than 2,500 genera, making up one of the largest and most commonly encountered of all beetle ...

in the subfamily

Chrysomelinae The Chrysomelinae are a subfamily of leaf beetles (Chrysomelidae), commonly known as broad-bodied leaf beetles or broad-shouldered leaf beetles. It includes some 3,000 species around the world. The best-known member is the notorious Colorado po ...

, native to Mexico.

Description

''Z. bicolorata'' is a small lead beetle with a brown head, brown and yellow graduated

pronotum The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum ( dorsal), the prosternum (ventral), and the propleuron (lateral) on e ...

and yellow

elytra An elytron (; ; , ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometimes alterna ...

marked with characteristic elongated brown stripes. The pattern on the elytra is greatly variable - in a study of 478 beetles, 29 variations on this pattern were identified.

Distribution and habitat

''Z. bicolorata'' is native to Mexico, but has been introduced to parts of India and Australia. Adults and larvae are used as a form of biological pest control in India in order to control invasive '' Parthenium hysterophorus ''.

Life cycle

Eggs are generally laid on the ventral surface of both young and old leaves, and occasionally on the upper surface of leaves, stems and flowers of host plants. Eggs are yellow to orange, elongate cylindrical or oblong with fine reticulations on the surface. The eggs hatch in 4–5 days. Larvae are pale yellow, turning white as they grow, feeding for 10 to 15 days on leaves whilst growing through four

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...

stages. On maturity the larvae enter the soil and pupate below up to 15 cm depth. The total life cycle of the beetle is just over 100 days.

Predators

An undetermined species of fly in the genus ''

Drino The Drino or Drinos ( sq, Drino, el, Δρίνος) is a river in southern Albania and northwestern Greece, tributary of the Vjosë. Its source is in the northwestern part of the Ioannina regional unit, near the village Delvinaki. It flows init ...

'' (family

Tachinidae The Tachinidae are a large and variable family of true fly, flies within the insect order Fly, Diptera, with more than 8,200 known species and many more to be discovered. Over 1,300 species have been described in North America alone. Insects in t ...

) has been recorded as parasitising ''Z. bicolorata'' in

Karnataka Karnataka (; ISO: , , also known as Karunāḍu) is a state in the southwestern region of India. It was formed on 1 November 1956, with the passage of the States Reorganisation Act. Originally known as Mysore State , it was renamed ''Karnat ...

(India). Two predatory bugs '' Andrallus spinidens'' and '' Eocanthecona furcellata'' prey on the larvae of ''Z. bicolorata'' and a third species, '' Sycanus pyrrhomelas'', preys on both larvae and adults.

References

{{Taxonbar, from=Q18385774 Biological pest control beetles Insects used for control of invasive plants Chrysomelinae Beetles of North America Beetles described in 1953