My stint with vermiculture over, I had another fortnight of study with
Dr K. Vijayalakshmi, whom my dad calls India's `Spider Woman'. Dr
Vijayalakshmi has been doing research on rearing spiders as a
biological weapon for controlling cockroaches and her workplace is full
of spiders of various types, all in bottles, and bred under her
supervision. An authority on spiders, she is also the author of a
well-known book on the subject.
Actually I had been anxiously waiting for a phone call from my parents
saying that the decks were cleared for my Crocodile Bank visit. Instead
Dad had phoned to say that the final arrangements for my stay at Croc
Bank were still being finalised and that I could use the 10 days or so
in between to learn what I could from Dr Vijayalakshmi about spiders,
and the unusual use she intends to put them to. I had readily agreed.
Dr K. Vijayalakshmi and her husband both work in an organisation called
the Centre for Indian Knowledge Systems (CIKS). CIKS is housed in a one
storey building and Dr Vijayalakshmi's office is on the first floor.
Here she studies various plants that are useful as pesticides and so
on. But I was not at all concerned with that aspect of her work.
In the garage of the building was the Spider Room-a laboratory of sorts
filled with bottles of different spiders in various stages of growth.
There must have been over 500 transparent plastic bottles at the time I
was there, each one neatly labelled, and all sitting one next to the
other with spiders in them. For air, each bottle had tiny pinholes in
its lid. Feeding was done through another small hole in the lid: this
hole was plugged with cotton. All these spiders and their activities
including growth, moulting, mating and hatching of babies were
monitored by Dr Vijayalakshmi. She had an assistant called Selvan and
he followed her instructions, keeping the records and making the
notings in a log book.
During the fortnight that I worked with Dr Vijayalakshmi, I simply
slipped into this set-up, reading books about spiders that Dr
Vijayalakshmi gave me, then learning to identify different spiders and
simultaneously helping Selvan in all the tasks that were needed to
maintain the huge spider population housed in the garage.
The spiders that Dr Vijayalakshmi deals with are called giant crab
spiders. These spiders do not build webs. They feed only on
cockroaches. The spiders were a little smaller than their prey i.e. the
cockroaches. I used to separate the babies, feed them, check the
moultings and catch flies for feeding them. I read a lot of books here
and sometimes caught the spiders in the garden in order to identify and
study them.
Spiders were not the only creatures housed in the garage. There were
also cockroaches bred in buckets with rolled cardboard in the centre
and broken biscuit pieces thrown in the bucket. The cockroaches were
fed once a week or so to the giant crab spiders.
The smaller spiders used to get flies to eat and these were caught by
us everyday from the garden. The flies have to be fed alive to the
spiders, so we used transparent plastic bottles to trap the flies and
once caught we would carefully put them into the spider's bottle.
Sometimes the spider would immediately catch the prey and eat it; at
other times the fly would buzz around in the bottle for days till the
spider was ready to eat it.
Dr Vijayalakshmi also bred a particular species of fly in a small cage
with fine mesh with a small saucer of milk in the centre as a medium
for breeding.
Baby spiders were also housed individually in bottles and these were
fed fly larvae or the larvae which come when maida or rava begins to
lose its freshness.
The purpose of all these experiments was to find out which types of
spiders were useful for using as pest control agents to deal with
cockroaches. Information about spiders such as their growth, hardiness,
their eating habits, reproduction etc. are important indicators of the
species of spiders that can be kept in houses as predators for
cockroaches.
Other than the spider work I tried to learn Tamil from Selvan but he
was keen to learn English from me and so both of us failed in learning
a new language and ended up speaking a cocktail of TamEnglish instead.
Extracts from Diary:
Spiders
26th November: Uncle Mano and I left for Dr Vijayalakshmi's office this
morning at 7 a.m. While Uncle Mano and Madam chatted, I read some
books. Madam then showed us her spider collection. She also introduced
me to Selvan. Before we left she gave me some books to take home to
read.
27th November: Watched how Selvan separated baby spiders from their
mother, placing each baby in a separate container. There were about 110
babies. Then we fed about 200 older spider babies. Selvan showed me how
to check their moulting.
28th November: Today I did feeding of the spider babies on my own. Then
transferred adults from one container to another and then fed them.
29th November: Today did only feeding of spider babies. Madam did not
come to the office as she was ill but her husband Dr Balasubramanian
came to check on us instead. Read some books on spiders in the
afternoon. Left early for home as Uncle Mano and Aunty Sagu were going
away for a few days and I would be staying at their relative Santosh
Kumar's place instead. They left at 7.30 p.m. and I waited at their
neighbour's place for Santosh to collect me which he did at 9 p.m.
30th November: Being Sunday I got up late and ate idlis, dosas and
sambar for breakfast. Wrote out my diary for the past 2 days and
watched some TV. In the evening Santosh took me to the bus stand and
explained the route I would have to take next morning to CIKS.
1st December: Madam came to the office today and showed me how to
collect spiders which were in the compound of the office. She also gave
me some more material to read on spiders and told me to start preparing
my essay on spiders. After doing a little bit of feeding as usual, I
went out on my own and collected few species of spiders. Then Madam
helped me identify them and also some other species of spiders that
they had caught. Spent the afternoon catching flies to feed to some of
the older spiders.
2nd December: Today I only did identifying of different species of
spiders. I took some material home to read and so I left early; was so
busy looking at the books I was carrying, I didn't notice the terminus
where I was to get off and got over carried much further. Had to walk
nearly half an hour back. Asked people for directions and finally
reached the terminus.
3rd December: Did not feel well today so I didn't go to CIKS. Read the
books I had brought at home. Started preparing my written report.
4th December: Today did feeding of spiders as usual. Then caught about
70 flies and fed them to the adult spiders. Put 2 spiders to mate and
made my observations. Continued writing my report in the evening.
5th December: Went to New College to collect my vermiculture report.
6th December: Did feeding of baby spiders first. Then caught flies. A
female spider's eggs had just hatched so Selvan and I did the
separation of the babies into individual containers.
7th December: Did writing of my report first today. Then I gave it to
Madam to correct. After she finished with it, I started writing it in
fair. I finished writing the report before evening and left it with
Madam for final approval.
8th December: Went to CIKS late as I had a bad stomach. I was given my
final report signed and Madam also gave me a certificate. I left
slightly early in the evening as I was still feeling unwell and was
scheduled to leave for the Croc Bank the next day.
Field Work Notes:
Spiders
These days most of us use Baygon or some other synthetic poison to
control cockroaches and other pests. But what does this do? It only
makes cockroaches or pests immune or resistant to such poisons.
Moreover, synthetic chemicals are very harmful and pollute the
environment. How nice it would be if we had a biological method of
controlling of pests. But that's just what spiders are!
A spider is not an insect. Insects are made up of a head, thorax and an
abdomen. They have compound eyes and are six-legged. They usually grow
wings in certain stages of their life and possess feelers or antennae.
Insects produce eggs which hatch into young that are completely
different from their parents. The young ones usually grow through
metamorphosis.
A spider on the other hand is an arthropod, made up of a cepolothorax
joined to an abdomen. It does not grow wings at any stage of its life.
It is eight-legged, and in place of the normal insect antennae it has
pedipalps. A spider generally has eight simple eyes or it could have
six eyes e.g. a spitting spider. Depending on the species the eyesight
may be well or poorly developed. Some species, such as the cave
spiders, are totally blind. Depending on the species a spider's life
span ranges from a couple of months to more than a decade (e.g.
mygalomorphs).
Almost all spiders have their first pair of appendages later modified
into fangs with venom glands. But only a few have fangs that are large
and strong enough to pierce human skin. Out of these, most cannot do
any serious damage to human beings except for about four to five
species which can be lethal.
The Black Widow spider, for example, which is found in South America is
the most poisonous of all spiders. The female of the species, whose
poison is strong enough to kill a human being, often kills and eats the
male after mating and is thus aptly named the Black Widow. This spider
is shiny black in colour with a red hour glass mark on the ventricle
side of the abdomen. Fortunately, there are no spiders in India which
can seriously harm human beings.
There are about 30,000 species of spiders in the world. They have been
found upto a height of 23,000 feet up Mount Everest as well as
underwater.
Almost all spiders are carnivorous. They can eat insects, small birds,
mammals and reptiles, including poisonous snakes and other spiders,
which they first subdue with their poison. They inject their prey with
a highly lethal venom and, having no teeth, suck out the liquid from
inside their prey. Large spiders with longer and powerful jaws may eat
part of or even the whole of their prey. Spiders can live without food
from a few weeks upto three months, depending on species, size, and
age. They obtain liquid from their food and thus do not need water.
Many spiders spin webs to capture their prey. However spiders also have
other means of capturing their prey. Some spiders spit a sticky web
onto their prey. Others live in burrows with trapdoors. Whenever they
feel hungry they come out and catch an unsuspecting insect. One species
attaches a sticky drop to one end of its silken thread and holds it
with its first three pairs of legs. When an insect passes by, the
spider waves the thread at the insect and ropes it in, as it were.
Some spiders sit on flowers and catch insects that come to collect
nectar. Others spin a small web, hold it with their first few pairs of
appendages and then throw it on insects passing below them. Still
others feed on other spiders only and are called pirate spiders. A few
spiders live on the webs of other spiders: they are too small to be
eaten by their host. They eat the small prey that get caught in the
web, thus keeping it tidy.
Spiders also have amazing defence mechanisms. Some spiders camouflage
themselves as a bird dropping. Others, as a dried yellow or black
rotting leaf or twig. And yet others resemble ants which are often
rejected by birds, reptiles and other insects. Some are even able to
change colour and shape, to some extent, to match their surroundings.
Some species build zigzag white coloured threads in their webs which
are visible to birds who avoid flying through the webs and damaging
them.
The male spider is smaller than the female, and is thus liable to be
eaten by his mate. So, the male uses many tactics to prevent his being
devoured by his mate. In some cases the male drums or pulls at the
strings of the web in a special code to announce that he is not a prey
or an enemy, but a sexual object.
Some spiders offer their mate a gift such as a juicy fly, wrapped in
silk. But it may well be taken back after mating and offered to another
female. Sometimes a male may even offer the female the empty husk of an
insect. Sometimes the male loosely binds the female with silk to
immobilize her before mating. Some species of male spiders may
patiently wait near the web of a female spider for weeks until she has
caught a prey, and then mate with her while she is busy feeding on the
prey. Sometimes, the male is so small compared to the female that the
female is practically unaware of him while mating and this gives him
protection.
Most spiders are solitary in nature. Each one builds its own separate
web. If one spider falls by mistake into another web, the bigger spider
will eat the smaller spider. However, there are some spiders called
social spiders that live together in one web. Sometimes there may be
hundreds or even thousands of adults and young ones living in one web.
Even if a single prey is caught (such as a small fly), all the spiders
will share the meal.
Spiders multiply very rapidly. After mating, an egg sac is constructed
and the internally fertilized eggs laid inside the egg sac which is
carried by the female with her palps and fangs. Fertilization of eggs
may be internal or external depending on the species. Within 15 to 20
days, 80% of the eggs hatch. (The eggs hatch into young spiderlings.
The new born spiders are similar to their parents, only smaller. The
spiderlings moult to mature.) After a gap of one week to ten days the
next batch of eggs is laid in a fresh egg sac, and fertilised with the
help of stored sperm. The female can do this three to four times
without mating with another male, although she will readily mate with a
male after the laying of every batch of eggs.
Spiders have proven themselves to be one of the best biocontrollers of
insect pests. Very few of us realize that spiders were, are and will be
laying traps for insects even after man has finally disappeared from
the earth.
How to Rear Spiders
Spiders have cannibalistic tendencies, i.e. if two or more are kept in
one container, they will prey on each other. Hence from birth, they
must be separated into individual containers.
Transparent plastic containers (size depending on the individual
species) can be used to rear spiders. A few pin-sized holes should be
made in the lid of the container as aeration holes. One big hole should
be made for dropping prey inside. It should be blocked with a piece of
cotton.
Baby spiders will eat culture foods such as Thrypolium, drosophilia,
fruit fly and house fly larvae. As they grow, they will eat house flies
and later on cockroaches.
Cleaning the prey remains and moults is a must. Two containers should
be used. Every week the used one should be washed with soap and water,
and allowed to dry in the sun.
The legs of the stands on which the spider containers are kept should
be placed in bowls of water or oil to avoid ants. The adults should be
fed well before allowing them to mate. Spiders will tolerate moderate
room temperature.
Culturing food
1. Milk powder and a medium sized piece of cotton, mixed with water.
Every day, a teaspoon of milk powder should be added.
2. Drosophilia larvae culturing: quarter cup of wheat flour and two
medium sized pieces of jaggery should be boiled in two cups of water.
Housefly and drosophilia can be reared in a wooden or metal framed box,
covered with a fine mesh or netting. The above mixture should be put
into small bowls and introduced into the cage. Adult houseflies and
drosophilia should be captured and put inside the cage and left there
to lay their eggs.
3. Thrypodium larvae: adults are found in rava and maida. A special
bucket should be kept with an aeration hole and the maida or rava in
the bucket, sprinkled with a little bit of water every day. A strainer
can be used to strain out the larvae wherever necessary.
4. Cockroaches: need a bucket with many big aeration holes, covered
with a fine mesh. A few rolls of paper can be placed vertically inside
the box for the cockroaches to climb on.