Mealworms act as magnets for many of Britain's common garden
birds that feed on insects, such as the Great
Tit (Parus major), Blue
Tit (Cyanistes caeruleus / Parus caeruleus)
and (European) Robin (Erithacus rubecula).
Both the Royal Society for the Protection of Birds
RSPB
and British Trust for Ornithology BTO
recommend year-round feeding of wild birds.
According to the RSPB, "... in recent years it has
become apparent that many birds are struggling to survive during the
breeding season because of the fluctuations in weather, intensive
farming and greater tidiness in gardens and all built up areas. By
feeding year round, we are giving birds a better chance to survive the
periods of food shortage whenever they may occur."
The essential requirements of a good mealworm feeder are that it:
- retains the mealworms
- keeps the substrate dry
- ensures the mealworms are visible to the birds
- provides easy access for the birds
- is easy to refill
- is easy clean
Mealworm retention
Mealworms are capable of climbing up rough surfaces, so it is
important the internal surfaces are smooth and steep,
otherwise they may escape before birds take them. I maintain a 1-2cm
layer of bran, or oatmeal, in the bottom which
provides sufficient cover for the mealworms.
Keeping the substrate dry
The overhanging pitched roof ensures that both the mealworms
and substrate
remain dry, even in windy wet weather.
Keeping the mealworms visible
The sides are made from transparent plastic. The ends have
circular openings with perches so birds can view the mealworms from
outside the feeder. The birds can readily
spot mealworms in the substrate.
Easy access for birds
In addition to the circular end openings, there are large
gaps above the plastic sides which provide easy entry and escape
routes.
Easy to refill
The gaps above the plastic sides are just big enough to get
your hand into,
making refilling easy.
Easy cleaning
The roof lifts off and the plastic sides slide out, to
provide easy access for cleaning.
Other foodstuffs
Though this bird feeder was originally designed to hold
mealworms, it can of course also be used to hold other foodstuffs such
as sunflower seeds, etc.
Mealworms are not worms at all, rather they are the larvae of the
Darkling Beetle (Tenebrio molitor)
which live in grain stores and are indigenous to temperate regions such
as Europe.
Darkling Beetles, like many other varieties of insects such as
butterflies, have four distinct develop stages: beetle, egg, larva and
pupa. Sexually mature adult beetles (ie in the imago stage) lay eggs
which hatch out as larvae. The larvae shed their skins a number of
times, as
they grow. Newly moulted larvae appear white, but they soon darken
to a light tan colour. The larvae then change into pupae by a process
known as metamorphosis and the pupae eventually metamorphose into
beetles. Initially, the beetles appear a light tan colour but their
exoskeleton quickly darkens, so eventually they appear jet black.
Mealworms thrive at room temperature in dry dark conditions. They breed
prolifically, so it is very easy
to produce your own supply to feed to garden birds, or reptiles and
amphibians. Mealworms may be kept on/in a variety of substrates such as
bran and oatmeal.
Mealworms left unattended will eventually transform into pupae which
will metamorphose into beetles.
The beetles soon mature, mate and lay eggs which are minute and
unlikely to be seen. Newly hatched mealworms
are tiny too and easily missed. Soon their bodies reach the diameter of
a pin and they can be seen unaided,
crawling through the substrate. The pupae gradually get bigger,
shedding their skins as they grow.
Mealworms can be kept in plastic boxes. Mealworms are vegetarian so
hardly produce any odour and are not unhygienic, however
it is a good idea to provide some ventilation, such as a mesh grill in
the lid, or simply some holes. I cut a hole in the lid and use a glue
gun to fix a grill. The substrate should be kept dry. I prefer to use
oatmeal, but mealworms readily thrive in other
substrates such as cereal, or bran. Mealworms need little moisture, but
can be fed small quantities of vegetable or fruit scraps from the
kitchen, from time to time. It is important not to let the scraps go
mouldy.
Mealworms become inactive below room temperature, however garden birds
don't seem to have any difficulty finding them in the substrate at the
bottom of the feeder during the winter, as they frequently root about
using their beaks. Before mealworms are fed to reptiles or amphibians,
they should be dusted with calcium powder
and from time to time a multivitamin/mineral supplement.
Ordinary mealworms (Tenebrio molitor) should not be
confused with so-called giant mealworms, or superworms (Zophobas
morio) which are indigenous to the tropical region of Central
and South America.
They live in rotting vegetation on the forest floor and hence like warm
damp conditions.
The larvae bore into rotting wood and create pupation chambers.
As the beetles are quite handsome and slow-moving,
they are often kept as pets in some countries such as Japan. They can
easily be kept in a terrarium that
contains some rotting wood and is kept warm and moist. Fish flakes are
an ideal source of food for them.
I have seen these beetles lay eggs in damp sand. It takes
about four weeks from the time that eggs are laid to when the tiny
larvae are large enough
to be seen by the naked eye, wriggling about in the sand.
A useful trick for getting giant mealworms to pupate is to use 35mm
film containers. Half fill with
bran and place a single larva in each container. Pierce the lids to
make holes for ventilation. Check the
containers from time to time. Eventually the larvae will curl up and
transform into a pupae, and then
later emerge as a beetles which can be released in your terrarium.
A terrarium can be be made quite attractive, and more habitable for the
beetles, by growing
a selection of ferns in it. Spray inside the vivarium daily,
preferrably with filtered water.
Whilst
giant mealworms can be fed to some birds, reptiles and amphibians, it
is important that
they are chewed and not swallowed whole, as the larvae are quite
voracious and may
remain alive after being eaten and attempt to eat their way out if fed
to an animal that is sick or weak.
Giant mealworms are unsuitable for small insectivorous birds
such as Great Tit (Parus major),
Blue Tit (Cyanistes caeruleus /
Parus caeruleus) and (European) Robin (Erithacus rubecula).
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