S. Mahunka szerk.: Folia Entomologica Hungarica 31/2. (Budapest, 1978)

rate and the frequency of detritus was negligible when compared with those of the other two. This picture shows a momentary situation. There may be deviation from it as it will be visible in the following. No significant difference can be found at the results of dissections made on specimens of lateralis collected on the 4th of February, 22nd of April, 29th of July and 25th of August (Table 4). Only the rate (0.5-2%) and frequency (10-22%) of algae were somewhat lower. Table 3. Rate of different gut content components in the samples of Sigara striata and S. falleni (5thJune, 1975). The numbers in parenthesis show the frequency of individuals Alga Detritus Animal body fluid Unidentified Number of guts % % % • % examined Sigara striata 4.5 (39) 0.3 (6) 95. 3 (100) 18 Sigara falleni 10.3 (70) 0.3 (0.5) 89. 5 (100) 20 Nevertheless, the composition of the food of the population on the 3rd of June was distinctly changed when compared to former ones. The rate of algae has grown significantly (38. 5%) to detriment of the animal body fluid (61%). The frequency of the two types of food was just the same (algae: 80%, animal body fluid: 95%). Table 4. Temporary variability of the rate of different gut content components of Sigara lateralis. The numbers in parenthesis show the frequency of individuals 4 February 22 April 1975 3 June 29 July 25 August Alga % Detritus % Animal body fluid % Unidentified % 1 (18) 99 (100) 0.5 (10) 0.3 (5) 99.3 (85) 38.5 (80) 61 (95) 0.5 (20) 2.2 (22) 1 (ID 96.8 (100) 1. 5 (15) 1 (5) 97.5 (100) Number of guts examined 11 19 20 9 20 EVALUATION OF THE DATA On the basis of the results of dissections we must regard these Sigara species as omnivorous, feeding mostly on food of animal origin. Their main food is body fluid of lower invertebrates (JANSSON and SCUDDER, 1112, ZWART, 1965, MARTIN, 1970, etc.). There are precedents of substantial increase in the rate of herbic food under natural circumstances (

lateralis on the 3rd of June). If these results are added to the statement of SZABO (1950) who regards lateralis and falleni distinctly as herbivorous and to the results of PUTSHKOVA (1969) who found striata to be mainly herbivorous, then it is most likely that these species have the ability to accommodate themselves to the food supply given. This statement is in ac-