26 MONTANA EXPERIMENT STATION BULLETIN 333 



which damage has been reported for the past four years. A 

 new occurrence was found in irrigated wheat at Malta. A field 

 laboratory was established at Big Sandy and observations made 

 during the summer months. Weedy fields provide the principal 

 hibernation quarters. The first eggs appeared in May and until 

 October there were only about two weeks when egg laying was 

 not observed. The peak of the second generation egg laying was 

 in July. The average number of eggs in each of several hun- 

 dred egg masses was 30, and hatching occurred in from 4 to 7 

 days, depending on the temperature. Humidity apparently had 

 little effect on hatching. The chalcid egg parasite, Telelono- 

 mous ashmeadi, was numerous. While some egg masses were 

 parasitized 100 per cent, the total parasitism of eggs collected in 

 the field was only 10 per cent. A small Melyrid beetle, Cololps 

 hipunctatus, was numerous and an active predator on the eggs 

 but its actual control value is doubtful. Three species of adult 

 parasites were reared from field collected bugs. These are the 

 tachinid flies, Gymnosoraa jtiliginosa, Cylindromyia armata, and 

 Senotainia vigilans. The latter two have not hitherto been reported 

 as parasites of Say's plant bug. Many of the adult parasites 

 overwinter as pupae in the hibernating host. Adult parasitism 

 of field collected bugs was 11.7 per cent. 



Spring burning of weeds and trash in infested fields, idle 

 lands, and weedy roadsides appears to be the only method of 

 controlling Say's Plant Bug. 



THE BEET VVEBWORM 



Beet webworms (see figure 3) appeared in great numbers in 

 1936 for the first time since the unprecedented outbreak of 1932. 

 There are usually two full generations of this insect in Montana. 

 The moths which develop from overwintering larvae appear in May 

 and early June, their eggs producing the first generation of 

 worms in late June and the first part of July. Moths from the 

 first generation of webworms occur late in Juh' and lay eggs for 

 a second generation of worms in August. It is the first genera- 

 tion of webworms which causes by far the greatest amount of 

 damage to field beets, gardens, alfalfa, peas, etc. 



First Generation, 1936 



The moth flight was light in most of the Yellowstone Valley, 

 and in Jefferson, Gallatin, Glacier, Toole, Flathead, Lake, Ra- 

 valli, and Beaverhead counties. 



