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Pseudococcus viburni (formerly Pseudococcus affinis (Maskell), and commonly known as the obscure mealybug and tuber mealybug) is a close relative of the grape mealybug (P. maritimus) and a pest of the vineyards of New Zealand,[1] the Central Coast of California,[2] and the tea gardens of northern Iran.[3] Unlike the grape mealybug, the obscure mealybug is not native to California, having most likely been introduced to the region from either Australia or South America in the latter part of the 19th century.

Taxonomy[]

The obscure mealybug is thought to have evolved in Australia or South America. Its history in North America is not clear; from 1900 (when P. maritimus, the grape mealybug, was first described) to 1960, the obscure mealybug was variably misidentified as or synonymized with P. maritimus, P. longispinus, P. obscurus Essig, P. capensis Brian, P. malacearum Ferris, and P. affinis (Maskell).[5] This taxonomic confusion has hampered attempts to trace the exact origin of the species, but its presence in both Australia and South America strongly suggests that it is of Gondwanan origin.

Morphology[]

Obscure mealybugs exhibit a high degree of sexual dimorphism; females are flightless, larger, and longer-lived than the winged males, who cannot feed and die immediately after mating.

Females[]

The bodies of nymphal and adult female obscure mealybugs are rectangular, with rounded anterior and posterior ends. Adult females range from 1-5mm in length.[6] Like all mealybugs, the obscure mealybug covers its body in a white, waxy secretion which accumulates in clumps along thin filaments protruding from its exoskeleton. This clumpy secretion lends the mealybug its characteristic mealy appearance.

Males[]

Male obscure mealybugs are tiny, fragile insects with long antennae and a single pair of wings. They bear a strong resemblance to common house flies, but have two white wax tail filaments.

Identification[]

It is important for vintners to distinguish between the obscure mealybug and its close relatives, the grape and vine mealybug. The obscure mealybug has longer, thinner, and more crooked filaments than does the vine mealybug, making the obscure mealybug look comparatively untidy.[4] The most distinctive feature of the obscure mealybug is the set of two to four exceptionally long caudal filaments growing from the posterior of large nymphs and adult females. The insect's waxy secretion accumulates heavily on these filaments, making it appear to have several long "tails".[8]

The obscure mealybug more closely resembles the grape mealybug than it does the vine mealybug, but the two can be distinguished by the color of the defensive fluid they secrete when disturbed; grape mealybugs secrete reddish-orange fluid, while obscure mealybugs secrete clear fluid.[9] When crushed, the obscure mealybug's body contents (guts) are pinkish-grey.

Life cycle[]

Mealybugs get their name from the fact that the body of the females from the third nymphal instar onwards are covered with a white waxy material in the form of powder, threads, spiky projections or platelets. Eggs are laid in a sticky, foamy mass of wax threads, called an egg sac. Once the batch of eggs is laid, the female dies. First instar nymphs are yellow-brown and not yet covered with wax. They are actively mobile and known as ‘crawlers’.

Second instar nymphs are darker and less active. From the second instar onwards the life cycle of males anf females is completely different. After the second instar, the males form a dark false pupa followed by a pupa in rapid succession. The actual pupa develops inside a white, cottony cocoon. After a complete metamorphosis, a winged male emerges from this pupa. The males lack mouth parts and are incapable of feeding. They have a brief lifespan during which they are wholly engaged in seeking females to fertilize.

The female second instar nymphs, on the other hand, settle on the leaf and begin to secrete wax, moulting to a third instar and then the adult female without a complete metamorphosis.

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