April, '15] 



McCOLLOCH: CHINCH BUG EGG PARASITE 



257 



important factor which influences the length of life, and food is the 

 next most important. During midsummer the average length of life 

 was about four or five days, but with the advent of cool weather it 

 increased to from 15 to 25 days. Seven parasites that emerged 

 about the middle of September lived over 60 days and one lived 78 

 days. Parasites fed on sweetened water lived much longer than those 

 that were not fed. 



Length of Life Cycle 



The length of the life cycle varies with the season of the year. Dur- 

 ing the early spring and late fall the life cj'-cle averaged from 30 to 42 

 days, while during June, July, and most of August it averaged about 

 16 days, with a range of from 11 to 23 days. Between May 6 and Octo- 

 ber 21, 4346 parasites were reared and the average length of the life 

 cycle was 18.3 days, with a range of from 11 to 42 days. 



Table 2 gives the length of the life cycle based on the period between 

 first oviposition and first emergence in the continuous hfe history study. 

 Table 3 gives the average length of the life cycle for all parasites 

 reared in each brood of the life history work. 



Table 2. Showing Length of Life Cycle in Life History Study 



Brood 



Firsi Oviposition 



First Emergence 



Length of Life 



1 



(3) 







2 



May 6 



May 27 



22 days 



3 



May 28 



June 11 



15 days 



4 



June 12 



June 28 



. 16 days 



5 



June 29 



July 15 



16 days 



6 



July 16 



July 31 



15 days 



7 



July 31 



Aug. 15 



15 days 



8 



Aug. 15 



Sept. 1 



17 days 



9 



Sept. 1 



Sept. 24 



23 days 



(3) The first brood of adults was present in the field prior to May 6. 



Table 3. Showing the Average Length of Life Cycle of All Parasites 



Reared 



Brood 



Source 



Date 



No. of 



Av. liength 



Range 



Parasites 



of Life Cycle 



Max. 



Miu. _ 



2 



From field collection 



5-6 to 9-7 



463 



Days 

 10.7 



Days 

 31 



Days 

 2 



3 



From 2nd brood 



5-28 to 7-31 



799 



16.0 



21 



12 



4 



From 3d brood 



6-11 to 8-4 



932 



16.0 



21 



12 



5 



From 4th brood 



6-29 to 8-8 



279 



16.4 



20 



13 



6 



From 5th brood 



7-16 to 7-31 



978 



15.7 



23 



12 



7 



From 6th brood 



7-31 to 8-10 



567 



16.0 



22 



11 



8 



From 7th brood 



8-15 to 8-29 



266 



20.0 



26 



16 



9 



From 8th brood 



9-1 to 9-10 



62 



28.0 



42 



23 



7 



