Estimates of 57 686 larvae infesting apple trees 1, 6, and 10 and 145 165 larvae infesting hawthorn trees 1, 6, 7, 8, and 12 were calculated by taking the sum across all collecting dates of 5x (the number of buckets of fruit collected from beneath apple or hawthorn trees on a given collecting day) x (the number of pupae sifted per tray of fruit subsampled from these buckets); the weighting factor 5 was used because each bucket contained 2.5 trays of fruit and only half the area under each tree was covered by ground tarps.
Rearing studies have estimated that the average egg to pupal development time for Rhagoletis pomonella infesting apples in the field is 32.6 d, while it is 22.3 d for flies infesting hawthorns (J.
The overlap between apple infesting larvae and the Biosteres melleus population on apples was 76.5%.
This was not true for maggots infesting hawthorns, which helps to explain the higher level of parasitoid attack in the hawthorn fly race.
In Experiment VIb, fly larvae infesting hawthorns with caterpillars or weevil grubs were found to be more prone to parasitoid attack, presumably due to their more peripheral positions within fruits.
With respect to Experiment VIb, 51.7% of fly larvae (n = 317) infesting hawthorns shared their fruit with either a caterpillar or weevil.
For hawthorn fruits without heterospecifics, 57.1% of n = 83 larvae infesting the smallest width category of hawthorns (1.2-1.5 cm) were parasitized, 37.3% of n = 150 larvae infesting the intermediate size class of hawthorns (1.6-1.7 cm) were attacked, while only 18.6% of n = 127 larvae in the largest hawthorns (1.8-2.0 cm) had parasitoids.
The results from this study indicate that Rhagoletis pomonella larvae infesting the derived host apple are much safer from braconid parasitoids than larvae infesting the ancestral host hawthorn.
Second, interspecific interactions are much less common and detrimental for flies infesting apples than they are for flies infesting hawthorns.
(Note: The magnitude of parasitism was low in Diehl's study because he stored collected fruit in a barn, thereby limiting the opportunity for wasps to attack fly larvae infesting the abscised fruit.)
cingulata larvae infesting its derived host sour cherry (3.3% = 30 eclosing parasitoids/916 eclosing parasitoids and flies) compared to its ancestral host black cherry, Prunus serotina (54.0% = 1625/3009).
(in press) show that intra- and interspecific competition is also reduced for fly larvae infesting apples.