346 MISSES K. FOOT AND E. C. STROBELL : RESULTS OF 



Fi Hybrids. — Thirty-two of this generation were hatched (see Record III. 

 p. 364) and 27 were safely reared through the five moults to the winged 

 stage. They hatched between June 4th and July 9tli, and reached the 

 winged stage between July 8th and August 3rd. 



As soon as they reached the winged stage {i. e. after the 5th moult) they 

 were transferred to a large cage and closely watched. As each pair mated, 

 they were isolated, while mating, to a separate cage, and kept isolated 

 throughout the entire breeding period. The eggs from these F. 1 pairs were 

 placed in wet chamber dishes as soon as they were deposited, and the F. 2 

 nymphs were carried through their entire development in these dishes, until 

 they reached the winged stage, when they were killed and preserved in 

 glycerine, as described on p. 371. 



On July 9th and 10th, seven of the Fj hybrid nymphs reached the winged 

 stage (3 ? & 4 (^). On July 19th two of these Fi hybrid pairs mated, each 

 pair being transferred at once to a separate cage while mating. They were 

 kept thus isolated through their entire breeding season (see Records lY. 

 and V.^ pp. 364-5). In this manner we isolated seven pairs of these 

 Fi hybrids. 



Records IV. to X. give the details of these breeding experiments, and a 

 brief summary of tlie results will show what features are typical of this 

 generation of Fi hybrids. 



Record IV. (p. 364). First Pair q/'Fi Hijhrids. — 169 eggs were deposited 

 from August 2nd to August 31st. The pair mated 14 times, and eggs were 

 deposited 7 times, and not oftener than once or twice between two matings. 

 Six of the 169 eggs were killed for cytological study, and of the remaining 

 163, at least 154 hatched. (The number hatched is underestimated, as in 

 two cases, only those nymphs were counted that survived the first moult.) 

 96 of these nymphs were reared to the winged stage (46 cJ & 50 ? ). 



Forty-three of the males were photographed, and are shown on Plate 29. 

 Three of the males died in the cage just after the fifth moult. The ventral 

 surface, including the genital segment of these three males, was dark and 

 pathological, and of no value for the demonstration of the genital spot. 



A photograph of the male of this pair of F| hybrids is shown on 

 Plate 28, photo 9. 



Record V. (p. 365). Second Pair of Fi Hybrids. — 184 eggs were 

 deposited from August 1st to September 11th. The pair mated 25 times, 

 and eggs were deposited 10 times, and not oftener than once or twice 

 between two matings. 



The female was discovered August 1st sucking the group of 2^ eggs 

 she had just deposited. She had sucked the entire contents from seven 



