if it has just apeared then yes i would be inclined to think it was a nest of some sort.the thing is you would also see some of the ocupants if it was such a thing and i believe the grass mite suffer just above it . it could be an insect of the stinging kind remember so be carefull . again there would be ocopants flying in and out . if you dont see these after watching for a while i would go and smack the mound with a shovel hardish .step back in case there are bees or something as they will get defencive . if not go and see if theres lots of ants running round defending there nest . if none of these for sure i would take a sharp spade and dig down and investigate . is there any big trees near you as this could be a tree root . moles dont make blind hills they normaly pile the dirt up wear theres a mound . you havnt given a whole lot of information realy but if insects id of said you would definatly see evidance of the host. id think it was a tree root myself especialy if its just apeared.take care i hope ive helped bye for now .

Thanks for the info.Will do some investigating bearing in mind your tips and let you know what happens.

ok your more than welcome . i hope i helped ill keep my fingers crossed for you .

Its full of red ants.mound is on edge of lawn close up against flag stone path and they are under the path also.I am going to try Nippon.My neighbour suggests boiling water as a remedy?

well if you can totally flood them out you could use normal water but i dont know if it would get the queen who could actualy be 10 feet or more underground . i would use ant powder like you say nippon as the workers take it back and feed it to the young and the queen wear ever she is . im glad i helped and you didnt get stung . thanx for telling me and good luck . bye for now .

Many weeks later! made series of holes quite deep with fork and for a week poured hot water down them 3 times a day Also used Nippon all over site every other day. That made ground much softer and so was able to dig. it over,that revealed hundreds of ant eggs.but no live ants.Put some jeyes on soil and dug it in and raked it fine sowed grass seed.It is now the best bit of the lawn beautiful green patch,gave it a 1st cut this week.Been on hols ,visitors regular,
because we are not far from coast and Airport,sdo have been busy..Reading this back sounds a load of rubbish but hope you can get the gist of it.Thanks for your help

no i understand it deadhead lol . the ants are know more so thats good . as for being the greenest bit of grass thats know suprise . what people dont realise id jeyes fluid although its a dissinfectent and weed killer initialy breaks down and becomes bio friendly . a lawn food if you will . anyway im glad you got it sorted take care bye for now .