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Larve volkcev so sedentarni plenilci, med katerimi je kar nekaj vrst, ki gradijo pasti v obliki lijakov. V prvem delu naloge smo preučevali interakcije med larvama dveh vrst lijakarjev Euroleon nostras in Myrmeleon formicarius. Vrsti se v naravi pojavljata simpatrično. V prvem poskusu smo kompeticijo med dvema larvama povečali, tako da smo 15 dni hranili le eno larvo v paru, nato smo režim hranjenja spremenili. Larve E. nostras so, ne glede na hranjenost, ob prisotnosti M. formicarius bolj povečale lijake kot v kontrolnem poskusu, kjer so bile v posode nameščene posamezno. Larve M. formicarius so v interakcijah lijake manj povečevale, hkrati pa so se več prestavljale in so bile pogosteje brez lijakov. Pri večji gostoti larv sta se obe larvi pogosteje prestavljali, pogostejši je bil tudi pojav znotrajcehovskega plenilstva. Ne glede na hranjenost obeh larv v paru, so larve E. nostras v interakcijah pogosteje zmagale kot larve M. formicarius. Sklepamo, da lahko različen odziv larv obeh vrst na pomanjkanje hrane pomembno vpliva na kompeticijsko uspešnost posamezne vrste. V zadnjem poskusu smo pare larv 24 ur snemali in analizirali videoposnetke. Opisali smo 14 novih osnovnih vedenjskih vzorcev, ki so vključeni v direktne interakcije med larvami obeh vrst volkcev. Kot sedentarni plenilci so larve volkcev odvisne od aktivnosti plena, zato je pomembno, da vsako priložnost čim bolj učinkovito izkoristijo. V drugem sklopu naloge smo preučevali odziv larv E. nostras na povečano pristnost plena. Opazovali smo hranjene larve 2. in 3. stadija ter stradane larve 3. stadija. Larvam smo v lijak v kratkem časovnem zaporedju spustili dve mravlji. Večjih razlik v odzivu na nov plen med skupinami nismo opazili. Larve so se večinoma na nov plen odzvale le, če so prvega že usmrtile. V kolikor je bil prvi plen še živ, novega niso poskušale uloviti. Nekatere larve prvega plena niso takoj izpustile, ampak so začele lučati pesek v nov plen, medtem ko so v čeljustih prvega še zmeraj držale. Samo stradane larve so zmeraj izkoristile oba plena, hranjene larve pa so prvi plen vrgle iz lijaka ali ga pustile ležati v lijaku, ne da bi ga do konca izsesale. Antlion larvae are sit-and-wait predators which build conical pit-fall traps in sandy soil. In the first part of our experimental work we investigated competitive interactions between two pit-building antlion species Euroleon nostras and Myrmeleon formicarius. Both species are often found simpatrically in sheltered habitats. In first experiment only one larva in each interspecific pair was fed. We changed the feeding regime after 15 days. E. nostras larvae always built larger pits when M. formicarius was present compared to a control group in which larvae were kept separately. Myrmeleon formicarius larvae built smaller pits, relocated more often and were often without a pit for several days during the interactions experiment. At higher larval density the relocation of both larvae was more frequent, there was also a higher percentage of intraguild predation. Irrespective of the feeding regime, E. nostras larvae won more often. We suggest that the difference in the response of both antlion species to prey shortage can have an important effect on competitive success of investigated species. Finally, we video recorded several pairs of antlion larvae during interactions in 24-hours interval. We described 14 new behavioural acts that occurred during larval interactions. Since prey encounter rates are often rare it is important that larvae use each prey as efficiently as possible. In the second part of our experimental work we investigated foraging behaviour of E. nostras larvae under higher prey availability. We compared the behaviour of fed second and third instar and starved third instar larvae. We fed each larva with two ants in a short period of time. There was no difference among larvae from different groups regarding their immediate response to the second prey. Most larvae dropped their prey and attempted to capture the new one, only if the first ant was already dead. If the first prey was still alive, they ignored the new prey. Some larvae did not drop the first ant immediately instead they started tossing sand in attempt to capture the new prey, while still holding the first ant in their jaws. Only starved larvae always fed on both ants before discarding them from the pit, while fed larvae of both instars frequently discarded the first prey without feeding on them again.