Corydalid Life Histories 113 



in a rearing cage, and the range and mean pupation dates were 

 recorded. 



Adults were collected at night by means of a black light trap. For 

 C. rastricornis, the trap was set out between 9 and 10 PM twice a week 

 during the emergency period to obtain a quantitative number of emer- 

 gents per hour. Various times wee sampled in hopes of finding the peak 

 period of emergence for C. pectinicornis. The range and peak emergence 

 times were registered. 



To determine fecundity, the thorax and head of each adult fishfly 

 was removed with microdissecting scissors. The abdomen was then cut 

 ventrally and the ovaries with the eggs teased out. All eggs were counted 

 and the length (mm) of the female's body was recorded. The mean and 

 range were computed for each species. 



RESULTS AND DISCUSSION 



Swamp environment . — The pH ranged from 6.0 in February to 7.3 

 in November; x = 6.8. Dissolved oxygen values ranged from 2.0 to 11 

 mg/ 1 in August and March, respectively; x = 6.0 mg/ 1. In July, a car- 

 bon dioxide value of 85 mg/ 1 was recorded versus 15 mg/ 1 in the win- 

 ter and spring. Carbonate alkalinity values ranged from 51.3 mg/ 1 in 

 December and January to 102.6 mg/ 1 in July and August; x = 73.4 

 mg/ 1. Total hardness ranged from 68.4 to 171.0 mg/ 1 in June and May, 

 respectively; x = 99 mg/ 1. 



Larval development .— Frequency histograms of head width indi- 

 cated that the life cycles of both species are univoltine (Figs. 1, 2). In C. 

 rastricornis, hatching probably begins in early June, but due to small 

 size and concealment larvae were not collected until the end of June 

 (Fig. 1). April was the last month larvae were found before they 

 pupated. Hatching of C. pectinicornis occurred in July, making this 

 month unique in that two different size classes of larvae as well as pupae 

 were found (Fig. 2). Apparently, two cohorts were present. 



Population range diagrams of larval head capsule widths show the 

 monthly growth of both fishflies (Figs. 3, 4). Chauliodes rastricornis 

 showed the greatest growth (66%) between June and October, while C. 

 pectinicornis had two growth periods, from July to October (106%) and 

 April to June (17%). Growth of both was retarded when the monthly 

 water temperatures averaged below 15°C (November through March). 

 The second growth period of C. pectinicornis corresponds with the 

 absence of C. rastricornis larvae from the swamp (Fig. 5). 



In North Carolina, Cuyler (1956) found prepupal C. rastricornis 

 and larval C. pectinicornis from March 28 to April 17. He collected C. 

 pectinicornis larvae on land in April even though no adults were found 

 until the second week in May. This leaves five weeks for the fishfly 



