FNZ 66 - Diaspididae (Insecta: Hemiptera: Coccoidea) - Popular summary
Henderson, RC 2011. Diaspididae (Insecta: Hemiptera: Coccoidea). Fauna of New Zealand 66, 275 pages.
( ISSN 0111-5383 (print), ISSN 1179-7193 (online) ; no. 66. ISBN 978-0-478-34726-5 (print), ISBN 978-0-478-34727-2 (online) ). Published 23 May 2011
Armoured scale insects
The armoured scale insect family Diaspididae is one of ten families of plant-sucking scale insects present in New Zealand. Unlike members of those other nine families, armoured scale insects do not produce the sugary exudate known as honeydew, and so they are not directly associated with the growth of sooty mould fungi in their habitat, nor do they support honeydew feeders such as birds, geckos, bees, and wasps in natural ecosystems. The reason for this lack of honeydew production is the first unique feature of the family – the stomach of armoured scale insects is not directly connected to the hind gut. They avoid the problem of dealing with large volumes of liquid from phloem sap by instead feeding on plant cells or parenchyma.
The second unique feature of the family is their armour or scale cover, in which they incorporate the cast skins of their juvenile moults, cemented together with waxes from various wax-producing ducts and pores. The third unique feature is the fused segments of the posterior part of the abdomen called the pygidium; this has special lobes on the margin that are said to act like trowels and often also brush-like appendages, and that help spread the waxes when the insect twists and turns during scale cover construction. Having a strong protective cover is important because armoured scale insects are legless and sedentary, except for the first crawler stage and the tiny adult males that only live for a few days.
The native (endemic) species are found only on native host plants and none are of economic importance or do any serious damage. Some of the endemic scale insects are quite host specific, for example, the two Anoplaspis species found only on rata and pohutukawa (Metrosideros), and leptocarpus scale found only on oioi (jointed wire rush). Among others with wider host ranges, Poliaspis and Symeria are perhaps the most species-rich genera. Oddly, while there are no records of armoured scale insects on southern beech (Nothofagus), felt scale insects (eriococcids) in contrast show a remarkable diversification there. Nearly all the endemic armoured scale species belong to the subfamily Diaspidinae, and there is just one species in the other subfamily Aspidiotinae, which is surprising compared with the many more aspidiotine members of the introduced fauna.
Introduced or adventive species arrived accidentally on plants brought by the first European settlers, and by 1879 six species, including greedy scale, oleander scale, and rose scale had established. Since then the adventive species total has reached twenty-one, plus eight Australasian species. A few species still manage to breach the border – most recently zamia (cycad) scale in 2004 and minute cypress scale in 2009. Some of the adventive species are cosmopolitan pests and can be problematic, mainly in citrus, apple, pear, and kiwifruit orchards. Only four of them have invaded natural ecosystems but they seem to do little damage there.