324 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



name of the " Hessian Fly." This retardation of development may, 

 if disregarded, lead to immense damage being done. 



The first figure is from a pliotograph showing the actual appear- 

 ance of a number of dan-iaged barley plants, such as first attracted the 

 attention of Mr. Palmer, who, like a sensible man, examined into the 

 cause of so many stalks being buckled down ; and by stripping off the 

 loaf-sheath at once disclosed the now well-known " flax-seed " puparia. 

 This, then, is the appearance presented by Hessian My attack. I am 

 particularly desirous of impressing this buckled-down appearance upon 

 all who take notice of their crops (fig. 115). 



The fly is a very insignificant creature, barely three-sixteenths of 

 an inch in length, of a slaty colour, and in its habits very shy. I have 

 seen only three or four specimens flying in the fields, and these but 

 a short distance above the ground. 



Fig. 115. — A Number of Barley Plants infested with the grubs of the 

 Hessian Fly. (Greatly reduced.) 



They emerge from the pupae in May, and after mating the female 

 lays its eggs (some 150 in number). Flying to a hanging leaf, 

 she settles upon its upper surface with her head toward the stalk, 

 and, bringing the tip of her body down, she protrudes her tubular 

 ovipositor until it rests along the channel of the mid-rib; an orange- 

 coloured cylindrical egg is extruded and adheres to the leaf ; the fly 

 moves forward a short distance and lays another, and so on until 

 four or five, sometimes more or less, have been laid. This process is 

 repeated upon other leaves until her supply is exhausted, when she 

 dies. Now all the eggs have been laid with the head end towards 

 the stem; so that, as soon as they hatch, the tiny maggots have nothing 

 to do but proceed along the channel of the mid-rib until they reach 

 the stem, when they force themselves between the leaf -sheath and it 

 until further progress is stopped by the knot. Here they turn their body 

 half-way round, bringing the mouth organs into contact with the stem, 

 against which they then commence to rasp, feeding upon the exudations. 



