If photo c is used it will require the caption "Adult female long-tailed mealybug. Copyright Nicholas Martin, Plant and Food Research.) Jenny Harris, of Balclutha Primary School asks :-
What is this bug that is killing my pot plant?
Nicholas Martin, an entomologist at Plant and Food Research, responded.
A close look at the base and underside of the leaves in the photograph shows white waxy material. A magnifying glass reveals some white bugs with long white â€˜hairsâ€™. The white wax and the length of the wax filaments are typical of a nasty pest of plants grown in greenhouses and outdoors, the long-tailed mealybug.
Mealybugs have long sucking mouth parts that are held in a rostrum under the body which is typical of a sucking bug insect. They belong to the family Pseudococcidae, which is in the superfamily, Coccoidea, that includes the families of scale insects. Unlike most scale insects, mealybugs have legs and can walk over their host plants at most stages of their life.
The body of mealybugs are typically covered with wax and usually have a few short wax filaments. Some, like the long-tailed mealybug, surround themselves with wax where they are feeding. The body has the three main parts of a typical insect, head, thorax and abdomen, though the boundaries are not obvious when viewed from the top. The head has a short pair of antennae, a pair of eyes and the rostrum containing the feeding stylets. On the underside of the thorax are three pairs of legs, while the abdomen contains the gut, genitalia and excretory organs.
Mealybugs feed by inserting the stylets into the plant. The two maxillary stylets form two tubes. A narrow one through which saliva is pumped into plant cells and a large tube up which the partly digested cell contents are sucked up into the gut. Excess liquid is excreted from the end of the abdomen. This liquid is often rich in sugars and is called honeydew. It makes plants sticky. Many ants like honeydew so â€˜milkâ€™ mealybugs.
The mature, mated, female sits on her eggs that are laid into a wax-lined chamber under her body. The eggs hatch into tiny larvae that look like a small mealybug. After the larval stage, females have two nymphal stages that look like small adult females. The pre-adult stages are called instars. The adult males are much smaller than the female, but they have one pair of wings. When the male second instar is fully grown it spins a long wax cocoon in which it passes through two non-feeding pupal stages. The adult male hatches from the second pupal stage and while in the cocoon, expands and hardens its wings and grows its two white tails. The male then searches for females with which to mate. If necessary it can fly to nearby colonies.
I am planning an internet factsheet on the long-tailed mealybug for publication in the New Year. It will list the 76 host plants recorded in New Zealand and the eight predators and twelve parasitoids known in New Zealand. Predators prevent plants being overwhelmed by the long-tailed mealybug, but donâ€™t stop it being a nuisance.
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