INTERESTING INSECTS

By N A Martin (2010, revised 2017)

Tasmanian lacewing, Brown lacewing, Aphis-lion

Austromicromus tasmaniae (Walker, 1860)

Eumicromus tasmaniae (Walker, 1860)

Hemerobius tasmaniae Walker 1860

Micromus froggatti Banks, 1909

Micromus perkinsi Banks, 1939

Neomicromus tasmaniae (Walker, 1860)

This adventive lacewing comes from Australia and is now widespread in New Zealand. It occurs in grassland, vegetable crops, field crops, cereals and other habitats with low-growing vegetation where the adults and larvae feed on insects.

Conservation status: The Tasmanian lacewing is widespread and not threatened. It is a useful biological control agent of aphids in many commercial and domestic crops.

The adults are brown with two pairs of hairy wings that are held roof-like over their bodies. They are 7.5-10 mm long, have small heads with large black compound eyes and long antennae that are held out in front. The adult and larval lacewings often hide during the day. They may live for 50 to 140 days.

Female lacewings prefer to lay their lozenge-shaped white eggs on plant hairs, spider webs or other fibres. Eggs are laid between midnight and dawn. The eggs are about 0.72 mm long. One end bears the micropile. Eggs are usually laid near infestations of prey. A long, mottled brown larva hatches from each egg. This first stage larva is about 1.8 mm long and has three pairs of legs that are used for walking. The first stage larva has large jaws at the front of the head that are used to catch their prey. As the larva grows, it moults (changes its skin). There are three larval instars (stages). All larvae look similar. The last larva is 7-9 mm long. The hollow jaws are formed from the mandibles and maxillae that are fused and form a siphon through which the larvae suck up their food.

When the last larval instar is fully grown, it finds a shelter in the litter and spins a loose cocoon. The larva in the cocoon moults into a pupa. Legs and wings can be seen within the pupa. It twitches if disturbed. Adults hatch from pupae and then mate. The length of time of each life stage depends on temperature, being shorter at higher temperatures.

Annual cycle

Tasmanian lacewings breed all year. All stages can develop at low temperatures, with developmental thresholds around 5-6°C. Population increase in spring and early summer is associated with the increased availability of prey. There is usually a decline in populations during summer due to the activities of other generalist predators and a parasitoid. In Canterbury there are probably 6-7 generations per year.

Walking and flying

Both adult and larval stages of the Tasmanian lacewing have three pairs of legs that can be used for walking. Adults have wings and can fly. Larvae hide at the bases of plants during the day.

Feeding

Adult Tasmanian lacewings visit flowers and feed on nectar. Both adults and larvae eat aphids and psyllids. They also occasionally eat small caterpillars and may feed on other small insects. Larvae will eat one another.

The jaws in the adult are used for holding and chewing the prey. The whole of the prey may be consumed. In the larva the jaws are hollow and are used to hold onto the prey and to suck up the body contents.

Adult of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae) with aphids. © Plant & Food Research. [Image: 3FR]

Egg of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae). © Plant & Food Research. [Image: 3FM]

Egg of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae), showing eye spots, legs and antennae of the developing larva. © Plant & Food Research. [Image: 3FS]

Eggs of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae), laid on a spider’s web. © Plant & Food Research. [Image: 3FT]

Eggs of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae) laid on hairs on a kumara stalk. © Plant & Food Research. [Image: 3FN]

Larva of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae). © Plant & Food Research. [Image: 3FO]

Larva of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae) feeding on totara aphid, Neophyllaphis totarae (Hemiptera: Aphididae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 28JA]

Cocoon of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae) with pupa. © Plant & Food Research. [Image: 3FP]

Cocoon of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae) with pupa. © Plant & Food Research. [Image: 3FQ]

The brown colour and shape of the wings allow adult Tasmanian lacewings to be distinguished from other species of lacewings in New Zealand. For example, Drepanacra binocula (Newman, 1838), a common Australasian species, has pointed forewings. Wesmaelius subnebulosus (Stephens, 1836), a species from the Northern Hemisphere, has oval, black wings.

An endemic species, Micromus bifasciatus (Walker, 1860), has wings that are the same shape, but the forewings have two strong oblique dark brown bands. This species appears to be associated with trees.

While the Tasmanian lacewing larva is obviously a lacewing, it is more difficult for non-experts to identify lacewing larvae to species level.

Adult Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae). © Plant & Food Research. [Image: 3FL]

Adult of Drepanacra binocula (Newman, 1838) (Neuroptera: Hemerobiidae), note the hook wing. © Plant & Food Research. [Image: 3FI]

Larva of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae). © Plant & Food Research. [Image: 3FO]

Lacewing larva, Drepanacra binocula (Newman, 1838) (Neuroptera: Hemerobiidae) feeding on pittosporum psyllids, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 3I2]

Hilson in his 1964 thesis gives details of pathogens, parasitoids and predators of Tasmanian lacewings.

Pathogens

A polyhedrosis virus disease affected Hilson’s colony of Tasmanian lacewings. The virus appeared to be associated with aphid skins and was most prevalent in autumn.

Predators

Hilson recorded spiders feeding on adult and larval Tasmanian lacewings. He also found psocids feeding on lacewing eggs and recorded ladybirds feeding on lacewing adults and larvae. There is recent evidence that hoverfly larvae feed also on lacewing larvae.

Parasitoids

Mature Tasmanian lacewing larvae may be parasitised by Anacharis zealandica Ashmead, 1900 (Hymenoptera: Figitidae). Several eggs of the parasitoid may be laid in a larva, but only one parasitoid larva develops in each lacewing larva. The parasitised lacewing larva spins a cocoon as normal, but instead of pupating after a few days, it stays as a larva. After about 20 days, a parasitoid larva emerges, having eaten the lacewing from the inside. The parasitoid larva has small mandibles and two rows of eight dorsal spines. The parasitoid larva usually pupates in the lacewing cocoon. It is white at first, but turns black before adult emergence. The adult Anacharis zealandica is shiny black and about 2.5 mm long.

In addition to this parasitoid, Hilson found evidence of Ichneumonid parasitoid. In recent studies, Inkaka quadridentata Girault, 1939 (Hymenoptera: Pteromalidae), has been reared from Tasmanian lacewing cocoons. There may be one to three Inkaka adults emerging from one cocoon, whereas there is only one Anacharis zealandica adult per lacewing cocoon.

Adult female Anacharis zealandica Ashmead, 1900 (Hymenoptera: Figitidae), a parasitoid of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae) and other lacewings in the same family. © Plant & Food Research. [Image: 3FH]

Adult female Anacharis zealandica Ashmead, 1900 (Hymenoptera: Figitidae) laying an egg in a mature larva of the Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae). © Plant & Food Research. [Image: 3FE]

Pupa of Anacharis zealandica Ashmead, 1900 (Hymenoptera: Figitidae) in a cocoon of the Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae). © Plant & Food Research. [Image: 3FG]

Pupa of Anacharis zealandica Ashmead, 1900 (Hymenoptera: Figitidae) exposed in a cocoon of the Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae). © Plant & Food Research. [Image: 3FF]

Adult female Inkaka quadridentata Girault, 1939 (Hymenoptera: Pteromalidae), a parasitoid of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae) on a cocoon of the lacewing. © Plant & Food Research. [Image: 3FJ]

Adult male and female Inkaka quadridentata Girault, 1939 (Hymenoptera: Pteromalidae), parasitoids of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae); the female is larger and has a more pointed end to the abdomen. © Plant & Food Research. [Image: 3FK]

This lacewing has been recorded feeding on many different species of aphids, some of which live on vegetable crops, cereals and grassland plants. It also feeds on psyllids living on crop plants and native plants. There are reports that it feeds on other small insects including caterpillars and ladybird larvae.

Biological control of pests

Biological control of aphids and psyllids can reduce the impact of these herbivores and the need to use insecticides when aphids and psyllids affect crop plants. Tasmanian lacewings are important predators in grassland, various vegetable crops and in the home garden. If pesticides are needed to control other pests, it is advisable to use chemicals that will have minimal harmful effects on the lacewings or to use them at a time when the lacewings are not present.

Tasmanian lacewings arrive on plants early in spring and are capable of controlling early infestations of aphids on vegetable crops, including lettuce and potatoes.

Hilson RJD 1964. The ecology of Micromus tasmaniae (Walker). Unpublished M.Sc. (Hons) thesis, University of Canterbury, Christchurch. VII + 100 p.

Miller D. 1971. Common insects in New Zealand. A. H. & A. W. Reed Ltd, Wellington, New Zealand. Good drawings of life stages of Micromus.

Syrett P, Penman DR 1981. Developmental threshold temperatures for the brown lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae). New Zealand Journal of Zoology 8(2): 281-283.

Tillyard RJ 1923 (1922). Descriptions of new species and varieties of lacewings (order Neuroptera Planipennia) from New Zealand, belonging to the families Berothidae and Hemerobiidae. Transactions and Proceedings of the New Zealand Institute 54: 217-225.

Valentine EW 1967. A list of the hosts of entomophagous insects of New Zealand. New Zealand Journal of Science 10(4): 1100-1209.

Peter Workman for information about the biology of this lacewing.

Graham Walker for additional information and helpful comments.

The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.

1 August 2017. NA Martin. Prey Table updated. Browse biostatus corrected. Common name added. Information Source, Miller 1971 added.

5 June 2015. NA Martin. Synonyms: 2 added. Life stages: moved adult photo, added larva photo. Recognition: added adult and larva photos. Prey: rewritten, table added.