100 INSECTS WHICH PREY UPON AGPJCULTUEAL PLANTS. 



a slaty colour on casting their skins the third time. They have 

 the power of emitting a thread from their mouth when alarmed, 

 by which they descend to the earth, and reascend when the 

 danger is over. Little cocoons are formed in the earth by them 

 in which they pass the pupa stage, and in three weeks a bright 

 orange-coloured fly escapes ; the females much larger than the 

 males. They feign death when touched, are lively during sun- 

 shine, but dull during cloudy weather. Powdered lime or soot 

 scattered over the leaves when wet will check their ravages, but 

 the most reliable method is to drive a regiment of vouno^ ducks 

 up and down the drills. They will snap up the caterpillars, but 

 must be kept moving or they will attack the leaves, so much 

 nitrogenised matter requiring to be " toned " with vegetable food. 

 Probably the ducks will require training to eat them at first ; 

 and this may be done by mixing some of the caterpillars with 

 grain. 



Ce\plius loygmceus (the Corn Saw-Fly). — This insect is of a 

 shining black colour, with large head and prominent eyes. The 

 abdomen is long and slender, with j^ellow margins to the 

 segments ; the legs are bright yellow, and the insect is about 

 one- third of an inch in length. The larva is apodous — that is, 

 destitute of feet — and of a yellowish white colour. The female 

 pierces the stalk of corn — mostly rye — below the first knot and 

 lays an egg ; the young gTub, when hatched, eats the interior of 

 the stalk and cuts through the knots ; the affected plants 

 speedily assume a ripened appearance, but if examined will be 

 found worthless. It descends into the stump when fully grown, 

 and becomes a pupa from which issues a fly in May. 



Ichneiimonidm. — The Ichneumon Plies are amongst the most 

 serviceable of the enemies of insects : nearly every one has a 

 parasite peculiar to itself and belonging to this family. Some 

 are very minute and others fully half-an-inch in length, and 

 they are usually distinguished by their long slender and reddish 

 abdomen. They generally lay their eggs in the caterpillar by 

 inserting their ovipositors into it while feeding, and the young 

 when hatched feed on the fatty substance of their " host," avoid- 

 ing by instinct the vital parts. In due time the larva assumes 

 the pupa condition, but instead of a perfect insect coming there- 

 from, the minute parasitic ichneumons issue from the dead 

 chrysalis of their victim. A familiar example is that of the 

 cabbage butterfly caterpillar, which is often seen when about to 

 become a chrysalis surrounded by a number of minute silky 

 cocoons which contain the ichneumons {Microgaster glomeratus) 

 that had lived in it. Care should therefore always be taken not 

 to destroy these useful little parasites. 



