132 Objects for the Microscope. 



in the stems of wheat and barley, but which is called the 

 frit in Sweden, where it occasions enormous loss as much 

 as one hundred thousand pounds sterling annually. This is 

 caused by the little innocent-looking Chlorops on the slide. 

 It effects this by simply depositing its eggs early in June on 

 the stem of the young wheat, which being as yet low in the 

 sheath, the little maggot hatches and feeds in the shelter of 

 a leaf, mines into the stem, but does not enter the hollow 

 part. It is well that it does not do so ; for we know that if 

 the cells of a plant are destroyed in the channel of its life, 

 which is the stem, of course it presently withers, or brings 

 forth but imperfect fruit. 



More harm would this insect do if its propagation was 

 not checked by a good little Ichneumon-fly (C&linius), 

 which is commissioned to destroy its larvaB by laying its own 

 egg inside the maggot of Chlorops, just as the Microgaster 

 does in the caterpillar of the Cabbage Butterfly, and thus 

 defends us from our tiny foe. 



These Chlorops frequent our windows, often in swarms 

 known by their large green eyes ; their yellow and black 

 bodies and beautiful wings lying along the body and ex- 

 tending beyond it. You can rarely mistake it ; and then if 

 you have this mounted specimen you will observe its pecu- 

 liar antennse, the third joint knobbed, the arista seated side- 

 ways upon it, and like a fine long bristle. The thorax 

 striped ; three broad stripes and one slender line on each : 

 outside of these a black dot on the side of the breast. The 

 scutellum was yellow ; the abdomen short, broad, with dark 

 bands, and itself pale greenish-black. 



Observe, in the wings, how the sub-costal . and medias- 

 tinal are joined in one strong vein, which meets the costal at 

 nearly half its length ; the cubital ending at the tip of the 

 costal; the radial ending at three-fourths of its length ; the 

 prcebrachial ending on the hind border, near the tip ; the 

 pobmchial ending at beyond half the length. There are two 

 transverse veins. 



This slide will help us to recognise both our enemy, 

 Chlorops teniopa, and our little window-friend, Chlorops 

 lineata. The abdomen of the latter has a yellow tip and 



