Occupation:
|
Predator
|
Value
to Gardener:
|
5/5 - Pest Controller and Pollinator
|
Danger
to Humans:
|
4/5 – They can sting when provoked
|
Availability:
|
5/5 – They’ll arrive or you can buy some
|
Quick
Intro
The wasp is likely an under appreciated garden helper. They are
one of a few insects that duel as a predator and a pollinator. If left unthreatened
they will be valuable additions to any garden.
 |
| Wasp morphology WikipedianProlific, Wikipedia |
Science Stuff
Wasps belong to the order Hymenoptera, which includes bees
and ants. The main difference between a Hymenoptera (Bees, wasps and ants) and
Diptera (Flies and mosquitoes) is the narrow waist for the Hymenoptera and
small spoon-shaped halters are present in Diptera.
 |
Wasps have biting mouthparts and an ovipositor (egg-laying
organ). The ovipositor can be modified to sawing, boring, piercing or stinging.
There are many different types of wasps, either specialising in a prey-item
(spiders and caterpillars) or by biology (larvae deposited in plant leaves,
creating galls or cuckoo wasps that lay their eggs in the nests of other
Hymenoptera). Here is a quick list of a few major wasp families:
Ichneumonidae (For lack of common name, I’ll make it Drilling
Wasps): These wasps have slender bodies and females have a long ovipositor
modified to bore holes into plant stems to reach the larvae upon which they
parasitise. Eggs are deposited into the larvae of moths, butterflies, flies,
other Hymenoptera and lacewings.
 |
| Ichneumonidae Dolichomitus imperator Oviposition |
Gall wasps: These are wasps that deposit their eggs in plant
material, causing localised swelling of the plant material and forms galls. These
wasps are considered pests in agriculture. Families include; Eucharitidae and Pteromalidae.
Pompilidae (Spider-hunting wasps): These wasps vary in size, depending on the prey items size. They are often black with bright orange and red markings. Spiders are caught, returned to the nest where larvae are deposited in the paralysed spider.
 |
| Pompilidae Spider-hunting wasps Sphictostethus nitidus |
Vespidae (Paper wasps): These are the most common wasps and
will be the main family discussed in this article. All species build papery
multi-celled nests of chewed wood pulp and saliva. They are highly social and
will defend their nests aggressively.
 |
| Vespula germanica Vespidae Paper wasp |
Eumenidae (Potter wasps): These are solitary wasps that excavate
burrows or use mud to make nests. They deposit their eggs in the nest before
introducing paralysed caterpillars.
 |
| Eumenidae Potter wasp |
Sphecidae (Mud daubers): This is a large family of solitary
wasps. They also create burrows or mud nests. Adults feed on pollen and larvae
are fed with insects. Females can sting, but are seldom aggressive. They can be
used as biological control agents in agriculture, depending on their prey
preferences.
 |
| Ammophila sabulosa Sphecidae Mud daubers |
One specific mud dauber that is regular visitors to my garden
is the Flowerpot wasp, Pseudoplisus natalensis. I recognise them by their ‘white socks’. Females dig
holes in the loose soil of the flower pots and bring leaf hopper (Ptyelus grossus) nymphs to the nest.
They are fascinating to watch, they will fling out dirt from their burrow,
leave and a few minutes later return with a paralysed leaf hopper to be store
in the dungeon J. Which
is great, because not only are the leaf hoppers a pest, but they have a nasty
bite to them when they sit on you!
Habitat
Wasps, especially, paper wasps have diverse habitats and are
found just about everywhere. Once a colony has been established, fertilised
females can overwinter and new colonies are founded in spring, resulting in a continuous
wasp presence.
.JPG) |
| Paper Wasp Belonogaster dubia |
Diet
Adult
paper wasps feed on pollen and make great pollinators, since they are larger
than bees and distribute more pollen to other flowers. Mine like the raspberry's flowers and since they’ve been pollinating it; the raspberry has given full fruits (all of the multiple flowers are pollinated and all set to fruit).
Adult
paper wasps feed their young on chewed caterpillars. This season (summer
2012-2013) I have had a major caterpillar invasion of epic proportions! I have
had about a 40% loss in tomatoes, all due to caterpillar feeding. The worst
part is that they will not eat one whole tomato until it is completely
consumed; they eat one or two holes in each tomato. This makes the tomato rot
and fall from the plant. Others have gotten into some leafy vegetables as well,
but luckily my trusty army of 1 persistent female wasp made off with all of
them (in one day!) before too many vegetables were lost. (The caterpillar were mostly moth
species, especially Chrysodeixis acuta,
Silver U or Tomato semi-loopers, I’ll do a full pest profile on these soon J).
1.jpg) |
| Paper Wasps Hunting Belonogaster dubia |
 |
| Silver U, Tomato semi-looper Chrysodeixis acuta |
Wasp SOS
Twisted-wing parasites: Is a highly specialised group of insects that resemble beetles. They
belong to the order Strepsiptera and are parasites that live within other
insects, mostly Hymenoptera and Hemiptera (True Bugs – stink bugs and the
like). Stylopid females penetrate the host cuticle, they become sessile and
remain in the body of the host and can be seen protruding from the abdomen.
After insemination of females by flying males, stylopid larvae consume their mother (hemocelous viviparity). The larvae are mobile, they seek out and
infect new hosts, where they moult into legless maggots that remain within the host,
feeding of nutrients in the blood. Along with abdominal deformities, the
parasites cause the host to become sterile and cause behavioural changes of the host.
Infected wasps do not perform social colony tasks, instead they leave the colony and gather
in clusters at suitable mating sites for the parasite. Female parasites of the
Xenos vesparum species do not exhaust their host's reserves and may overwinter
with their wasp host, whereas males exhaust their host’s reserves and the wasp dies at the end of the summer season.
 |
| Twisted-wing parasite Strepsiptera, Halictophagida Halvard, Wikipedia |
Wasps – last thoughts
Even
though they can be the stuff of nightmares, this season has made me realise how
under appreciated they really are (even more than mantids J) and
that can be excellent pollinators and great biological pest control.
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