1918] Leaf Eating Crane- Fly 73 



The actual method of oviposition was frequently observed. 

 The female rests on the under side of a leaf with the extremity of 

 the abdomen directed towards the leaf-edge. The abdomen is 

 slightly recurved vertically, and the margin of the leaf is grasped 

 between the bifurcated valve of the ovipositor which is applied 

 to the upper surface of the leaf, and the paired, cutting valves 

 the blades of which are apposed to the under surface. These 

 blades are then moved to and fro, and a slit is cut in the epiderm, 

 the recurved margins of the blades serving to widen the aperture 

 of the slit. The ploughshare, ventral valve then comes into play, 

 serving to guide the emerging egg into its position in the slit. 

 By reason of its being excavated internally, after the fashion of 

 a deep-keeled boat, this valve performs its function admirably. 

 The valves are then withdrawn, and the performance may be 

 repeated alongside the first slit, a number of these finally pro- 

 ducing the parallel-beaded arrangement of the eggs along the 

 margin. In no instance do the eggs actually touch upon each 

 other as one finds in the case of eggs laid in parallel series by 

 the leaf-mining species of the Pegomyia genus of Anthomyiid 

 diptera.* 



Duration of Egg-stage. — The period of incubation occupies 

 about two weeks. In the breeding-cages, eggs hatched in from 

 fourteen to eighteen days, and it is not unlikely that under 

 field conditions, the egg-stage endures for two to three weeks. 

 Records show that under experimental conditions, the first eggs 

 were deposited on May 22, and the date of first hatching was 

 June 7. The first, newly-emerged larva was taken at Westholme 

 on a leaf of T. grandis on May 31. 



The Embryo and Emergence of Larva. — The maturing embryo 

 is at first distinguishable within the egg by the appearance of 

 two dull, red spots, one on each side of the anterior extremity of 

 the egg. Presumably these indicate the position of the eyes. 

 Later, as the embryo develops, the black head-capsule stands 

 out quite markedly within the transparent chorion. 



The actual time occupied by the larva in leaving the egg is 

 about three hours. In its efforts to free itself, it is not at all 

 energetic. In one particular case, on June 7, the young larva 

 made slow movements from side to side, erecting its head and 



*Cameron, A. E. — A Contribution to a Knowledge of the Belladonna Leaf- 

 Miner, Pegomyia hyoscyami, Panz. its Life-History and Biology. Ann. App. Bio. 

 Vol. I, No. l,"May 1914, London, p. 57. 



