C. K. Lilly, D. L. Ashley, and D. C. Tarter.
Observations on a Population of Sialis itasca Ross in West Virginia (Megaloptera: Sialidae).
Psyche 85(2-3):209-217, 1978.

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OBSERVATIONS ON A POPULATION OF
SIALIS ITASCA ROSS IN WEST VIRGINIA
(MEGALOPTERA: SIALIDAE)
BY C. K. LILLY', D. L. ASHLEY~, AND D. C. TARTER* Observations on the ecology of each species in an aquatic community are necessary for the total understanding of community dynamics. Several authors, including Davis (1903), Ross (1937), Townsend (1939), Flint (1964), Azarn and Anderson (1967), Wood- rum and Tarter (1973), Pritchard and Leischner (1973), Tarter and Woodrurn (1973), Tarter (1973), Tarter et al. (1976), and Tarter et al. (1978) have reported on the taxonomy, distribution, life history, and ecology of several Sialis spp. Other authors, including Roback and Richards0.n (1969), Warner (1971), Nichols and Bulow (1973), Tarter and Woodrurn (1972) and Woodrurn and Tarter (1973), have noted the extreme tolerance of Siafis to acid mine drainage. The primary objectives of this investigation were: (1) to make observations on the life history and ecology of the alderfly S. itasca in a small farm pond and (2) to determine the pH tolerance of this population under laboratory conditions.
MATERIALS AND METHODS
The population of S. itasca inhabits a small farm pond, 0.1 hectare, near Shoals, West Virginia which is 8 krn south of Huntington, West Virginia. This pond is located in the north-central region of Wayne County. It is located at 82029'40f'W longitude and 38' 21'50f'N latitude.
This investigation was initiated in May 1975 and continued until April 1976. Monthly samples were taken by a small seine (0.25 inch mesh). The seine was placed in the water vertically and the mud and debris on the bottom of the pond between the seine and the bank were disturbed. The seine was then moved toward the bank while dragging the bottom of the net on the bottom of the pond collecting 'Present address: 4074 - 40th Street, Nitro, WV 25143 aept. of Biol. Sci., Marshall Univ., Huntington, WV 25701 Manuscript received by the editor August 1, 1978. Pu&e ÌöS:20SI-21 t 1978). http:llpsyche cnlclub orBig5Ìö5-20 html



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2 10 Psyche [June-September
mud and debris in the net. The larval alderflies were collected and preserved in 70 percent ethanol.
Temperatures were taken with a Taylor maximum-minimum thermometer placed on the pond bottom 0.5 rneter below the water surface. They were recorded in degrees Celsius once per month at the time benthic samples were taken. Water chemistry tests were performed in the field with a Hach chemical kit, Model AL-36- WR. All tests were completed within one hour. Hydrogen-ion concentration (pH) was rneasured colorirnetrically. Dissolved oxy- gen, carbon dioxide, hardness (magnesium and calcium), phenol- phthalein and methyl orange alkalinity, free acidity, and total acidity were rneasured and recorded in rng/ 1. Size classes were deterrnined by length frequency distributions arranged in 1 rnrn length groups. Total length (exclusive of the caudal filament) was rneasured under 7X magnification with calipers and a plastic ruler (nearest 0.5 rnrn). Head width was rneasured with an ocular micrometer between the inner edges of the eyes (nearest 0.01 rnrn). Differences in head width of 124 larvae were deterrnined to show the mean, range and standard deviation. A total of 84 foreguts were exarnined to deterrnine food habits. The head was rernoved and the abdomen was split open to remove the intestine. The contents of the intestine were rernoved and exarnined under a dissecting microscope and a compound rnicro- scope to identify their contents. The percent frequency of occur- rence of each item was deterrnined, and the monthly and seasonal averages and various sizes were compared. For the pH tolerance test, forty mature larvae collected from the pond in April were taken to the laboratory for acclimatization over a 24 hr period. The larvae were placed in groups of 10 in 4 finger bowls. One bowl was filled one-third of the way with pond water. A one molar solution of potassium dihydrogen phosphate (KHzPO4) was diluted approximately into the other three bowls, to set pH values at 5.5, 4.0, and 2.5. The pH value of the control was 7.0. A Model 5 Corning Scientific pH rneter was used to deterrnine pH values. Oxygen was constantly supplied with air stones. The ternper- ature did not change significantly during the experiment and averaged 12 C. The 96 hour TLm (median tolerance limit) test (APHA, 1965) was used to measure the effect of low pH. The pH value at which 50 percent of the alderfly larvae died after 96 hours was deterrnined by straight-line graphical interpolation.



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19781
Lilly, Ashley, & Tarter - Population of Sialis itasca 2 1 1
Fifteen larvae were collected in April and returned to the laboratory for rearing in vials containing pond water. These vials were connected to vials containing sand by a short section of rubber tubing (Pritchard and Leischner, 1973). Wire mesh and strips of foam rubber were placed in the vials and rubber tubing to enable the larvae (one per vial) 'to move freely between the vials. The vials were kept at room temperature which was approximately 70 F. Fecundity was determined by a direct count of ovarian eggs under a compound microscope. The ovaries of 3 adults were removed and a total of 1616 eggs were counted. The diameters of 90 eggs were measured to the nearest 0.01 rnrn with an ocular micrometer using a Bausch and Lornb compound microscope.
RESULTS AND DISCUSSION
Pond Environment
Temperature. - The average annual temperature for the pond was 18.1 C. The extreme monthly temperatures were 0.5 C in February and 35.0 C in August and September. Water Chemistry. - The average annual pH was 8.4 (7.5 to 9.0). The average annual dissolved oxygen was 8.5 rng/ 1 (6.5 to 10.0). The average annual total hardness was 139.6 rng/ 1 (102.6 to 153.9). The average annual carbon dioxide concentration was 9.6 rng/ 1 (5.0 to 25.0). The average annual alkalinity was 110.5 rng/ 1 (68.4 to 145.4). The average annual total acidity was 12.4 rng/ 1 (5.7 to 28.5). Larval Stage
Development. - Length-frequency histograms indicated that the population of S. itasca contained one size class (Fig. 1). Hatching occurred at the end of May. There were 18 egg masses located in the field at the end of May. The egg masses were found on the leaves of hornbearn and buckeye trees. Three egg masses which were returned to the laboratory hatched within 2 days. In July all the egg masses were empty but no larvae were located. The earliest and smallest larvae were collected on August 2, 1975. Their average length was 6.45 rnrn, and their average head width was 1.02 rnrn. The last and largest larvae were collected on April 6, 1976. Their average length was 13.67 rnrn, and average head width was 1.59 rnrn. Head width was used to show the monthly variation in growth rate and the percent increase in growth rate (Fig. 2). Due to the



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Psyche [June-September
6 14
BODY LENGTH
Figure 1.
Length-frequencies at monthly intervals of S. itasca larvae from a farm pond near Shoals, W. Va. The number of larvae is given for each month.



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19781 Lilly, Ashley, & Tarter - Population of Siah itasca 213 small sample size (4) in August, no statement can be made concerning the growth rate frorn August to September. An eighteen percent increase in growth rate was recorded from October to November. There was a decrease in growth rate in December. Small sample sizes in January (2) and February (6) prevented any growth rate information. There was a six percent growth rate from March to April. The largest mean head width was measured in April at 1.59 rnrn and ranged between 0.95 and 1.86 rnrn September and Novern- ber, respectively. No larvae were located in May, June and July. Woodrurn and Tarter (1973) also found a decrease in growth during the winter months in S. aequalis. Azarn and Anderson (1969) found a decrease in the growth rate for S. rotunda and 5'. californica during the winter months.
M J J A S O N D J F M A
Figure 2. Monthly variation of the head width in S. itasca larvae. Vertical lines = ranges, horizontal lines = means, open rectangle = one standard deviation, numbers = sample sizes, and dotted lines = temperature (C).



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214 Psyche [June-September
Food Habits. - This population of S. itasca was found to feed almost exclusively on the ostracod, Cyclocypris sp. The only other food items were 3 midges, Chironomus sp., which were found on 3 different occasions. Of the 84 foreguts analyzed, 21 percent were empty and 79 percent contained food. Ostrocods were found in 71 percent of the foreguts, and midges were found in 4 percent of the foreguts.
Excluding the month of August when a very small sample size (4) was used, the largest number of empty foreguts occurred in January (50%). The percent of empty foreguts increased again in April supporting the findings of Woodrurn and Tarter (1973) in S. aequalis that the larvae probably do not feed just before pupation. Azarn and Anderson (1969) reported S. rotunda and S. cali- fornica to be indiscriminate feeders and reported cannibalism to be frequent. Woodrurn and Tarter (1973) found S. aequalis to be more restricted in its feeding due to the limited choices of organisms found in the acid mine stream in which they were located. They also reported cannibalism to occur to a lesser extent. The S. itasca in this investigation were found to be more restrictive feeders preying almost exclusively on ostracods while having an abundant supply of other organisms upon which they could feed. Cannibalism was observed in the laboratory when larvae were confined for three days without food.
Predation. - The stomachs of 18 odonates and 10 sunfish were examined. No alderfly remains were found in the sunfish and only one alderfly head was found in the odonates. Schwiebert (1973) noted that the hellgrarnrnite and trout are predators of the alderfly. pH Tolerance. - The 96 hour T L value for S. itasca was found to be 3.1. All ten larvae survived the 96-hour period at pH values of 7.0 and 5.5, 70 percent survived in a pH of 4.0, and 30 percent survived at a pH of 2.5. Tarter and Woodrurn (1972) found S. aequalis from an acid mine stream to have a T L value of 2.1. These values would indicate that S. itasca and S. aequalis are quite tolerant of low pH. Sialis spp. have been noted to be tolerant to low pH conditions in western Pennsylvania streams (Roback and Richardson, 1969), Roaring Creek in eastern West Virginia (Warner, 1971), and in the East Fork of the Obey River in Tennessee (Nichols and Bulow, 1973).




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19781 Lilly, Ashley, & Tarter - Population of Sialis itasca 2 15
Pupal Stage
Larvae placed in the laboratory rearing chambers moved to the sand for pupation within 2 to 4 days. The pupal stage lasted for approximately 2 weeks. The adults emerged during the night. No pupae could be located in the bank of the pond. Azarn and Anderson (1 969) reported S. rotunda and S. californica to pupate during April, May and June. Pritchard and Leischner (1973) reported that S. cornuta pupated from May to rnid-June. Woodrurn and Tarter (1973) found S. aequalis to crawl 1.5 to 5 rn out of the water onto a moist sandbank when the water temperature reached 11 to 13 C and pupated in an earthen cell 1 to 7 crn below the surface. They found the pupae to respond to a disturbance but otherwise remained rather dormant.
Adult Stage
Number and Size of Eggs. - Fecundity of 3 adult alderflies showed a range of 454 to 587 eggs per female; the average was 539 eggs. The eggs were cylindrical, rounded on the ends, had a curved rnicropylar tubercle on one end, and averaged 0.31 rnrn in length by 0.14 rnrn in width. The number of eggs found in S. itasca was similar to those of S. aequalis (657) (Woodrurn and Tarter, 1973), S. rotunda (300-500) and S. californica (400-700) (Azarn and Ander- son, 1969), and S. cornuta (615) (Pritchard and Leischner, 1973). Egg masses of S. itasca were found on the underside of hornbearn and buckeye leaves 0.5 to 3 rn above the water surface. The eggs are laid in rows in a nearly vertical position rnuch like those of S. rotunda (Azarn and Anderson, 1969).
Mating. - Although copulation was not observed, a courtship behavior was observed in the laboratory rnuch like that described by Azarn and Anderson (1969) for S. rotunda and by Woodrurn and Tarter (1973) for S. aequalis.
Longevity. - Adults in the laboratory lived for 4 to 6 days. Only one adult was captured in the field on 3 May 1975. Sialis rotunda was first seen in rnid-April and reached their peak in May (Azarn and Anderson, 1969) while S. californica was seen in May but did not peak until rnid-June (Azarn and Anderson, 1969). Sialis aequalis was observed in the field between April 21 and May 4 (Woodrurn



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21 6 Psyche [June-September
and Tarter, 1973). Since the adults serve only to reproduce the species, it is apparent that they have a brief life span to perform this function. Azarn and Anderson (1969) observed the female of S. rotunda laying eggs within a day after emerging. AMERICAN PUBLIC HEALTH ASSOCIATION, INC. 1965.
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New species and new state records of Sialis (Neuroptera: Sialidae). Ent. News 25: 9-13.
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Effects of acid mine drainage on the stream ecosystem of the East Fork of the Obey River, Tennessee. J. Tenn. Acad. Sci. 48(1): 30-39. PRITCHARD, G., AND T. G. LEISCHNER.
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Low pH tolerance of the larvae of the alderfly, Sialis aequalis Banks, under controlled conditions. Proc. W. Va. Acad. Sci. 44: 85-88. 1973.
First record of the alderfly, Sialisjoppa Ross (Megaloptera: Sialidae), in West Virginia. Proc. W. Va. Acad. Sci. 45: 163-164. 1973.
Distribution and new record of the alderfly Sialis (Megaloptera: Siali- dae) in West Virginia. Ent. News 84: 147-148. TARTER, D. C., D. L. ASHLEY, AND C. K. LILLY. 1976.
New record of the alderfly Sialis itasca Ross for West Virginia (Meg- aloptera: Sialidae). Ent. News 87: 32.
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Lilly, Ashley, & Tarter - Population of Sialis itasca 217
TOWNSEND, L. H.
1939. A new species of Sialis (Megaloptera: Sialidae) from Kentucky. Proc. Ent. Soc. Wash. 41: 224-226.
WARNER, R. W.
1971. Distribution of biota in a stream polluted by acid mine drainage. Ohio J. Sci. 71: 202-216.
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1973. The life history of the alderfly, Sialis aequalis Banks, in an acid mine stream. Arner. Midi. Nat. 89: 360-368.




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