praying mantis . by B G Furner . a trial in Kent as a form of biological pest control . 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 . an eye-witness described one sprayed area as literally rank with the stench of small game and birds dead from insecticide poisoning . 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 . 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 . both native and imported predatory insects and insect pathogens are used in field trial tests . the biological control of pests in the garden is not new to the American gardener . ladybirds figure in press advertisements , their sale being by the gallon . praying mantis ( Mantis religiosa ) , both native and immigrant varieties , are used by gardeners in all parts of the United States . advertisements offer eggs of European , Chinese or native forms of mantis . 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 . nine blowflies may be consumed at one sitting and the fully adult , 2 1/2-in.-long insect , is able to keep a firm hold on one grasshopper while eating another . according to Dr Max Beier in fangheuschrecken ( die neue brehm bu&quot;ckerei , 1952 ) , the praying mantis is trecking northwards . the northward journey of the mediterranean mantis brought the insect to Frankfurt on Main by the middle of the 18th century . from Frankfurt this useful insect has spread eastwards to Brno in Czechoslovakia and westwards as far as Fontainebleau . in north America the northward drive has brought the mantis to Ontario . there is , therefore , the possibility that within 100 years the praying mantis may be a part of the Kentish fauna . with this in mind , I started my trials with praying mantis in Kent last spring . 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 . the young mantis started to hatch in batches until mid-June . swathed in a tight membrane , from which all the baby mantis do not escape , the 1/2-in.-long insects look rather like a cross between an Egyptian mummy and a space pilot . after extricating itself from the membrane , the young mantis has to dry itself . it is at this stage that the helpless insect is in great danger - especially from ants . I found that neither sticky bands nor tanglefoot deterred Kentish ants . to study the mantis more closely , I transferred some from the peach trees to a Kilner jar . 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 . I was able to keep my mantis alive in the jar by introducing a daily supply of fruit flies . 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 . 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 &apos; diet by American writers . perhaps the mantis has to be at the adult stage before it will tackle these insects . after the first moult , the mantis were somewhat lighter in colour - a change from emerald green to leaf green . I need not remind readers of the cool , very wet weather of late July , August and September , 1960 . the weather conditions led me to feel quite certain that no praying mantis could possibly live through them . but on September 18 , to my very great surprise , I came across a praying mantis on a blackberry leaf . the colour had changed again - to that of the adult , a yellowish-brown . however , the mantis had not yet reached its full size , being only 1 1/4 in in length and still wingless . the mantis was photographed and then released . now the finding of one mantis is , in my opinion , a very hopeful sign . it is estimated that out of every 1,000 eggs laid , only six mantis survive until the autumn . 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 . but if the one mantis I found in the autumn were the only survivor , the survival ratio was high , at around 1 : 100 . my gravest error was in the choice of the species of praying mantis with which I started off my trials . 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 &amp;deg; F in the shade . it is at present too early to report on my continued trials with this useful predator . a British zoologist and entomologist suggested that I try Spanish mantis this season . 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 D Antonio Ben&amp;iacute;tez Morera of Cadiz . the first batch of around 50 mantis hatched from this egg-case on June 20 . meanwhile Mr Moncrieff had sent me an egg-case of the Chinese mantis . the first mantis had hatched from the very large egg-case on June 6 . both the Chinese and Spanish mantis , in the young stage at any rate , are light brown in colour . 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 . a gardener s chronicle reader living in Grantham , Lincs , kindly offered to cooperate with me in studying praying mantis as a pest control in the cold greenhouse . 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 . 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 S&amp;eacute;rignan to find his specimens . local boys here in Kent , possibly distracted by my crop of grapes and blackberries , show no interest in searching for praying mantis to earn 5 s for each mantis found - dead or alive . a choice of pots . by John T Warren , N.D.H . despite the steady influx of substitutes since the end of the war , clay pots are still in greatest demand . 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 . 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 . 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 , and where the handling and storage facilities are not too good , these losses will be even greater . 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 . the storage problem puts clay pots at a definite disadvantage . 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 . 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 . 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 . 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 . 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 . clay pots are efficient and congenial containers in which to grow plants . in their proper setting they are not unattractive and , in spite of their shortcomings , most gardeners have a nostalgic affection for them . present-day pots are better finished , do not get dirty so readily and are easier to wash . the deep rims make for neater and safer stacking , though they are still expensive and still get broken . 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 . soil blocks are probably the oldest alternative to clay pots for plant raising . these are compressed blocks of compost , made in a specially devised press to simulate roughly the shape and size of a pot . 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 . 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 . 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 . one big advantage of soil blocks is an obvious one : the cost of a pot of any description is saved completely . manufacturing the block and planting it is very little more trouble than normal potting , and a superior plant , which transplants more easily , is produced . 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 . 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 . 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 . 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 . there are many types of plastic pots available ; some expensive , some quite cheap ; some good and others not so good . a wide range of plants grow quite well in plastic pots and usually need less water than those in clay pots . they are slightly more difficult to manage , however , until a little experience has been gained with them . plastic pots are usually more expensive than clay ones , but they are almost indestructible and will last a long time with normal care . 