PRAYING MANTIS .sx By B. G. FURNER .sx A TRIAL IN KENT AS A FORM OF BIOLOGICAL PEST CONTROL .sx WE have not yet reached the stage in Britain when 50 planes are engaged in spreading 1,500 tons of DDT and fuel oil over 3 million acres or when 20 million acres are sprayed with dieldrin .sx An eye-witness described one sprayed area as literally rank with the stench of small game and birds dead from insecticide poisoning .sx Wholesale chemical spraying , upsetting as it does the balance of nature by killing both pests and predators , is viewed with concern by a number of American State Research Stations .sx Not content with issuing bulletins on the dangers of the misuse of chemicals in agriculture , some stations are carrying out useful research on pest control by biological means .sx Both native and imported predatory insects and insect pathogens are used in field trial tests .sx The biological control of pests in the garden is not new to the American gardener .sx Ladybirds figure in press advertisements , their sale being by the gallon .sx Praying mantis ( Mantis religiosa ) , both native and " immigrant " varieties , are used by gardeners in all parts of the United States .sx Advertisements offer eggs of European , Chinese or native forms of mantis .sx From the day it hatches in the spring until it dies in the late autumn , the praying mantis satisfies its voracity by eating other insects .sx Nine blowflies may be consumed at one sitting and the fully adult , 2 1/2-in .sx -long insect , is able to keep a firm hold on one grasshopper while eating another .sx According to Dr. Max Beier in " Fangheuschrecken " ( Die Neue Brehm " ckerei , 1952 ) , the praying mantis is trecking northwards .sx The northward journey of the mediterranean mantis brought the insect to Frankfurt on Main by the middle of the 18th century .sx From Frankfurt this useful insect has spread eastwards to Brno in Czechoslovakia and westwards as far as Fontainebleau .sx In North America the northward drive has brought the mantis to Ontario .sx There is , therefore , the possibility that within 100 years the praying mantis may be a part of the Kentish fauna .sx With this in mind , I started my trials with praying mantis in Kent last spring .sx The 1960 summer was not suitable for the start of a trial with mantis , but I did not know that when I tied the egg-cases to my peach trees in early May .sx The young mantis started to hatch in batches until mid-June .sx Swathed in a tight membrane , from which all the baby mantis do not escape , the 1/2-in .sx -long insects look rather like a cross between an Egyptian mummy and a space pilot .sx After extricating itself from the membrane , the young mantis has to dry itself .sx It is at this stage that the helpless insect is in great danger- especially from ants .sx I found that neither sticky bands nor tanglefoot deterred Kentish ants .sx To study the mantis more closely , I transferred some from the peach trees to a Kilner jar .sx According to Dr. Max Beier and to American writers , young mantis feed on plant lice , but I found that my young mantis could not be tempted by aphis from elder , peach and fat hen .sx I was able to keep my mantis alive in the jar by introducing a daily supply of fruit flies .sx By July 12 , the growing mantis showed a decided preference for house-flies and blow-flies , but their appetite increased until the few flies I was able to catch were quite insufficient , so I had to release the mantis in the garden .sx I see from my records that the mantis in the jar at no time showed any interest at all in young grasshoppers , moths or caterpillars- all of which are claimed to be a part of the mantis' diet by American writers .sx Perhaps the mantis has to be at the adult stage before it will tackle these insects .sx After the first moult , the mantis were somewhat lighter in colour- a change from emerald green to leaf green .sx I need not remind readers of the cool , very wet weather of late July , August and September , 1960 .sx The weather conditions led me to feel quite certain that no praying mantis could possibly live through them .sx But on September 18 , to my very great surprise , I came across a praying mantis on a blackberry leaf .sx The colour had changed again- to that of the adult , a yellowish-brown .sx However , the mantis had not yet reached its full size , being only 1 1/4 in .sx in length and still wingless .sx The mantis was photographed and then released .sx Now the finding of one mantis is , in my opinion , a very hopeful sign .sx It is estimated that out of every 1,000 eggs laid , only six mantis survive until the autumn .sx I feel certain that if one of my mantis survived others also survived among the mass of grape-vines , blackberries and other fruits and vegetables on my 1/8 acre .sx But if the one mantis I found in the autumn were the only survivor , the survival ratio was high , at around 1 :sx 100 .sx My gravest error was in the choice of the species of praying mantis with which I started off my trials .sx The egg-cases , which my good friend , Mr. J. O. Moncrieff , export manager of the well-known American seed firm , W. Atlee Burpee and Co. , kindly sent me were of the Arizona species , Stagmomantis limbata , Hahn , accustomed to dry summer temperatures reaching 120@F .sx in the shade .sx It is at present too early to report on my continued trials with this useful predator .sx A British zoologist and entomologist suggested that I try Spanish mantis this season .sx My colleague in Madrid , Dr. D. Fernando Quintana , had great difficulty in obtaining an egg-case , but one was finally secured through the kindness of Sr .sx D. Antonio Beni@2tez Morera of Cadiz .sx The first batch of around 50 mantis hatched from this egg-case on June 20 .sx Meanwhile Mr. Moncrieff had sent me an egg-case of the Chinese mantis .sx The first mantis had hatched from the very large egg-case on June 6 .sx Both the Chinese and Spanish mantis , in the young stage at any rate , are light brown in colour .sx Because of the cool , wet weather , I had great difficulty in breeding fruit flies and , after many of the mantis of both types had died in my Kilner jars , I poured living mantis over vines and peachtrees .sx A Gardeners Chronicle reader living in Grantham , Lincs , kindly offered to cooperate with me in studying praying mantis as a pest control in the cold greenhouse .sx Of the dozen Spanish mantis sent him by post on June 22 , only two or three survived the journey ; one thrived and the latest report I have is that this mantis is still alive .sx Since June I have not seen a mantis in my garden and I would dearly like to know how J. Henri Fabre persuaded local children at Se@2rignan to find his specimens .sx Local boys here in Kent , possibly distracted by my crop of grapes and blackberries , show no interest in searching for praying mantis to earn 5s .sx for each mantis found- dead or alive .sx A CHOICE OF POTS .sx By JOHN T. WARREN , N.D.H. .sx DESPITE the steady influx of substitutes since the end of the war , clay pots are still in greatest demand .sx It is mostly in the smaller sizes that the substitutes have made headway , and although numerous small clay pots are used each year , they are fewer than they were 10 years ago .sx In the larger sizes there is still no real substitute for clay that can be obtained at a comparable price , except the bituminized paper pots which are used on commercial nurseries for growing tomatoes and chrysanthemums .sx The main disadvantage of the clay pot is its brittle nature ; even with reasonably careful handling , the annual losses are often around 10 per cent .sx , and where the handling and storage facilities are not too good , these losses will be even greater .sx This does not necessarily apply to the larger sizes , as they are not quite so fragile as the smaller ones and are not normally thrown about in quite the same way .sx The storage problem puts clay pots at a definite disadvantage .sx They are fairly heavy and difficult things to accommodate and they must have some protection from severe weather , which can be quite a headache in a small garden .sx While admitting that broken pots have on occasions provided artists with delightful studies , there is no doubt that a pile of badly stacked , half-broken pots is an unlovely sight from any point of view .sx Every garden boy will agree that having to wash clay pots is a definite factor in favour of their abolition ; in fact one young man was so wholehearted about this a few years ago that he made the headlines for having smashed a large number to relieve his feelings .sx On the small-to-medium establishment , it is a disagreeable chore which nobody tackles with any enthusiasm , whereas on larger establishments the pots can be sterilized or washed by machine .sx It is not easy to make an economic comparison between clay pots and the various substitutes ; the former may last indefinitely with luck , while the latter are often expendable used only once .sx Clay pots are efficient and congenial containers in which to grow plants .sx In their proper setting they are not unattractive and , in spite of their shortcomings , most gardeners have a nostalgic affection for them .sx Present-day pots are better finished , do not get dirty so readily and are easier to wash .sx The deep rims make for neater and safer stacking , though they are still expensive and still get broken .sx On the other hand , there is really no replacement for the larger sizes , so they have the decided advantage of being the only suitable container available in quantity for fairly large plants .sx Soil blocks are probably the oldest alternative to clay pots for plant raising .sx These are compressed blocks of compost , made in a specially devised press to simulate roughly the shape and size of a pot .sx Usually cylindrical or hexagonal in shape , they are made of the same compost as would have been used in a pot , the only difference being that it is used in a slightly moister condition .sx Seed is sown , or seedlings are pricked out into them in the normal way , the only real difference being that more of the watering is done through a rose to avoid breaking the blocks with a spout of water .sx First-class plants of tomatoes , cucumbers , marrows , melons , cauliflowers , celery and onions , may all be raised in soil blocks ; so can such flowering plants as dahlias , chrysanthemums , salvias , sweet peas , lupins and numerous others .sx One big advantage of soil blocks is an obvious one :sx the cost of a pot of any description is saved completely .sx Manufacturing the block and planting it is very little more trouble than normal potting , and a superior plant , which transplants more easily , is produced .sx The obvious limitation is that soil blocks can only be used for propagating ; there can be no progression to a larger block when the plant or seedling is ready to be moved ; it must be planted out or potted .sx Many amateur gardeners might improve their results by buying a small hand-operated soil block maker and use the money saved on buying small pots to improve their composts .sx The various types of small paper pots are very useful for short-term operations , but are inclined to collapse if the plants are in them too long .sx They are quite useful for plants that are despatched to market or direct to customers , their cheapness making them attractive to the nurseryman ; there is also considerable saving in carriage costs because of their lightness .sx There are many types of plastic pots available ; some expensive , some quite cheap ; some good and others not so good .sx A wide range of plants grow quite well in plastic pots and usually need less water than those in clay pots .sx They are slightly more difficult to manage , however , until a little experience has been gained with them .sx Plastic pots are usually more expensive than clay ones , but they are almost indestructible and will last a long time with normal care .sx