56 MASS. EXPERIMENT STATION BULLETIN 150. 



It will be observed that the relative number of parasites obtained from 

 the flowed bog and from the dry one shows a similar condition, as regards 

 the amount of parasitism present on dry and flowed bogs, as that which 

 has alread}' been found to prevail with the natural enemies of the fire- 

 worm. From a study of the life-history of Phanerotoma tibialis, however, 

 it is not easy to see just how the flowage can affect its prevalence to so 

 marked an extent. 



It was found that the adult Phanerotoma lays its egg in the egg of the 

 fruit worm. It was not difficult to get one of these parasites to lay its egg 

 under observation, by bringing near it a berry bearing, under one of the 

 lobes of its blossom end, an unhatched fruit-worm egg. During their 

 laying season these parasites are constantly running over the vines with 

 actively vibrating antennae, searching for the eggs of the fruit worm, and 

 when a fruit-worm egg is presented to one of them, if the parasite's antennae 

 sense its location, it will give immediate attention to it, and the whole 

 process of egg-laying may be observed. A peculiar fact discovered was 

 that one of these parasites will never lay twice in the same fruit-worm egg. 

 One of them can, however, be readily induced to lay an egg in a fruit- 

 worm egg which already contains one or even several (twelve was the 

 highest number reached in any test) eggs deposited by other individuals. 

 It is not known whether the egg of the parasite hatches before the fruit- 

 worm egg does or not, but at any rate the fruit worm when it emerges 

 from the egg carries the small parasite with it, and as the fruit worm grows, 

 the parasite within it also grows, feeding upon its juices and so depleting 

 its vitalit}'^ that when it becomes full grown and forms a cocoon around 

 itself for the winter it is often but little more than half the size of a normal 

 unparasitized worm. Some time during the winter or spring the parasite 

 larva becomes full grown, and, emerging from the fruit woraa, leaves it a 

 mere dead shell, and forms its own tiny white cocoon about itself within 

 the cocoon of the fruit worm. Within its cocoon it changes into the pupa 

 stage, and it eventually emerges as an adult parasite nearly a j^ear after 

 it was deposited as an egg in the egg of the fruit worm. 



The second most important parasite which was reared is a small Ich- 

 neumon, which lays its egg in the fruit worm after the worm has hatched 

 and is already working in the berry. The name of this species has not yet 

 been determined. The female in laying its egg inserts its egg-laying 

 apparatus into the hole in the berry made and left open by the fruit worm. 

 This parasite was never seen to drive its egg-laying apparatus through 

 one of the white silken curtains which the worm usually makes over the 

 mouth of its hole after going into its first or second berry. The life-history 

 of this parasite has not yet been worked out to any extent. It is certainly 

 a far less important enemy of the fruit worm than is Phanerotoma tibialis. 



A large quantity of wormy berries was collected in August for the pur- 

 pose of making a detailed study of some of the immature stages of these 

 parasites, particularly of Phanerotoma tibialis. 



