Hod Hill is one of the most well known Iron Age hill forts in the county.  The site is thought to have been originally settled when the vast Iron Age complex on the neighbouring Hambledon Hill became  difficult if not impossible to defend from attack.  The encampment at Hod with its extensive ramparts eventually succumbed to attack by the 2nd Legion Augusta of the Roman army under the command of the future Emperor Vespasian.  The site's excellent defensive position was emphasised by the construction of a small fort by the victors within the existing Iron Age ramparts.Today we can see not only the 21 hectare (52 acre) Iron Age fort but also the well defined earthworks of the 4.5 hectare (11 acre) Roman camp, situated on the level hilltop in the north-west corner of the earlier fortification.  Little has happened to the hill since that time until the late 1930's.  About this period a perimeter fence was erected.  One must assume that the hill and the immediate area around it, at least, were open downland.  This fencing, and its effects on the grazing of the site, have been held responsible for the loss of Britain's rarest downland butterfly from the site, the Silver-spotted Skipper, last seen here around 1939-40.  During the Second World War an extensive area inside the ramparts was ploughed up, excluding only the earthworks, quarry pits and an area in the south-east corner of the enclosure.  This cultivated area was allowed to revert to grassland after the war.  It is still quite easy to distinguish this relatively young turf from the 2,000 year old turf in the unploughed areas.From the mid-sixties to the mid-eighties the southern and western ramparts were enclosed as two reserves of the then Dorset Naturalists' Trust.  In 1985 the site was purchased by the National Trust.  Since then internal and rampart top fences have been replaced by a single fence circumnavigating the entire hill-top.  Management is now based on a mixture of sheep and cattle grazing.  Although less "hit and miss" than previously, problems exist trying to cope with the hill's abnormally high fertility without damaging any of the flora and fauna.Like many other chalk sites, the hill has its own variation of the typical chalk downland turf, distinguished here by the abundance of Rock  Rose.  Many of the typically scarce flowers of chalk downland exist on the hill, but no great rarities.  This also applies to the butterflies present, the most important of these being the Marsh Fritillary.  As the name suggests, this is not a typical downland butterfly.  It is thought that the decline in sheep grazing and the subsequent change in emphasis to cattle grazing around the turn of the century led to changes in the turf community.  One plant able to make use of this change of grazing animal was Devilsbit Scabious, which is the plant most acceptable to Marsh Fritillaries and their larvae.  The colony of this butterfly on Hod Hill, established in the late 1920's, is thought to be one of the oldest on chalk downland in the country.  In the current trend of positive, though cost-conscious, conservation this butterfly on chalk grassland is proving difficult to maintain.  To an extent this is due to the fact that the cattle available today are virtually all derived from large continental breeds and these do considerable damage to historic earthworks, which regretfully seems to mean a return to sheep based grazing on some of these traditional cattle sites.  Other important butterflies found on the hill are the main chalk downland Blues, Adonis, Chalkhill and Small Blues together with the Brown Argus.  Of further interest are the larvae of the Grizzled Skippers, which exist here on a food-plant not recognised in butterfly books, namely Salad Burnet.  The day-flying moths should not be forgotten; Burnets can be found in good numbers, as can the migratory Silver Y, but most other "large" moths, like the Common Forester, Burnet Companion and Mother Shipton, are not well represented.The hill is crossed by two rights of way, a bridle path running diagonally from the north-west entrance to the south-east entrance, and a footpath from the south-east entrance to the south-western corner (the original entrance) via the top of the  outer rampart.The route taken by those recording butterflies covers not only the areas good for butterflies but some that are naturally poor, not only in numbers seen, but also in species present.  This gives us a fuller picture of the hill and its butterfly population.  Because the intention behind the walk was to observe butterflies, the route tends to keep to the bottom of the sunny side of banks and ramparts.  Good views of surrounding countryside may be had from the tops of many of the adjacent banks and ramparts.

SECTION 1: OUTER DITCH OF WEST RAMPART (Length 200m).

From your start point in the north-west corner, continue straight forward (south), taking the middle of the three ditches commencing at this corner.  If this is impassable due to Stinging Nettles, take the adjacent ridge for some twenty metres.  Keep close to the foot of the steep rampart bank on your left.  This is part of the main egg-laying area of the Marsh Fritillary, on the wing mid-May to mid-June, but is  also the home of many other butterfly species as well as a good range of downland flora.  This section continues until it intersects the ditches of the Roman fort:  you will see a small pathway veering up the bank to your left, which marks the start of Section 2.

SECTION 2: SOUTH SECTION OF WEST RAMPART DITCH (Length 200m).

This is a little more sheltered than the preceding section and is therefore more likely to hold a greater number of butterflies.  Continue as above until you reach the Purbeck stone steps.  Ascend these and this part of the walk ends at the top of the steps.  Look up occasionally to see whether you can spot Buzzards, and listen out for Skylarks.

SECTION 3: WEST QUARRY PITS (Length 150m).

Having reached the top of the steps, you will see before you some of the quarry pits excavated during building of the ramparts; note in them the difference in the growth in the bottom of the pits and on their basically south-facing banks.  The long herbage to your right will be used most by territorial males and to a lesser extent by egg-laying female Small Tortoiseshells, Peacocks and possibly also Marbled Whites and Ringlets, though few of the latter exist at this site.  The warm south-facing banks with their short plants will be used mostly by egg-laying female Blues, Small Coppers, Brown Arguses, Small Heaths, and Dingy and Grizzled Skippers.  In fact species requiring a warmer, drier habitat for their immature stages. Proceed along the bottom of these banks, meandering with their curves, until you reach the gap in the ramparts that is part of the south-western entrance, turn right and proceed through the gap into the next section.

SECTION 4: SOUTH-WEST TRIANGLE (Length 250m).

Once through the gap, turn right again, coming back on yourself on the other side of the rampart; follow the perimeter of this roughly triangular area, walking the ditch if possible, or the ridge if not.  This section, being fairly open, is apt to be somewhat variable in its butterfly population, it being virtually non-existent in poor summers, but superb in good summers; the area can literally buzz with insect activity.  Heading back almost to the gap by which you entered the section, turn right into the ditch between the two southern ramparts.

SECTION 5: DITCH OF INNER SOUTH RAMPART (Length 150m).

Once again the first few yards may be hazardous due to the Stinging Nettles.  Follow along in an easterly direction at the foot of the inner rampart.  This south-facing slope, once you are out of the shadow of the trees, is the major area for butterflies on the hill.  All thirty species present on the hill can usually be found here in reasonable numbers.  The section ends after 150 metres where a small slip has partially blocked the bottom of the ditch.

SECTION 6: EAST END OF SOUTH RAMPART DITCH (Length 150m).

This is a continuation of the preceding part of the walk, taking you to the south-eastern entrance.  On reaching here, bear left as the end of the rampart turns inwards.  The section ends at the apex of the rampart.

SECTION 7: (THE ALTERNATIVE STARTING POINT) EAST QUARRY PITS (Length 300m).

Turn left up the track and left again, coming back on yourself along the upper side of the rampart; walk along the bottom of the south-facing banks of each pit until you almost reach the gap in the ramparts at the junction of Sections 3 and 4.  In reasonable weather, most of the pits will contain a variety of butterflies.  However in a typically English summer only the last two or three may be sufficiently sheltered for butterflies.

SECTION 8: FORMERLY PLOUGHED CENTRE OF FORT (Length 300m).

Having arrived more or less parallel with the gap in the ramparts, turn sharp right.  Now this is the tricky bit where the unwary become lost.  For a variety of reasons, it is impracticable to use markers and you must therefore head off in a north-easterly direction, gradually curving to the left, to arrive at the south-east corner of the Roman camp.  This is situated approximately 200 metres north-north-east of the end of Section 7.  This is one of the poorer sections of the walk.

SECTION 9: SOUTH RAMPART OF ROMAN FORT (Length 200m).

On arriving at the correct location you will be able to see that the earthworks here consist of an outer ditch, a ridge and then another ditch.  The route now travels westwards along this inner ditch at the base of the inner south-facing bank.  It then crosses the southern gateway of the Roman fort with its flanking balista platforms and continues to within two or three metres of the inner western rampart of the Iron Age fort.  Although all the best plants exist here, growing in a nice, short turf and on a sunny bank, this section is much too exposed to be of any great value to butterflies.

SECTION 10: INNER DITCH OF WEST RAMPART (Length 200m).

There should now be the beginnings of a ditch running away northwards from your current position.  Follow this ditch so you are running parallel with Section 1, with the superb views of the Stour Valley to your left.  The main interest here, as in Sections 1 and 2, is the Marsh Fritillary which uses the bank to the right as one of its egg-laying sites.

SECTION 11: SOUTH BANK OF INNER NORTH RAMPART (Length 200m).

Cross the bridle path at the north-west corner of the hill fort and now walk along the bottom of the south-facing bank of the inner rampart.  This bank is undoubtedly one of the driest areas of the hill and you should be able to observe the difference in the turf.  The section ends where the outer ditch of the Roman fort cuts the inner Iron Age rampart:  go to the very end of the track to avoid a steep scramble down the bank, and turn left down into the ditch between the inner and middle rampart.

SECTION 12: MIDDLE NORTH RAMPART (Length  200m).

For the foolhardy and the butterfly recorders who undertake to walk Hod Hill every week from April to September to monitor butterfly numbers this section follows the nettle-choked ditch westwards to the end of the walk at the north-west corner of the hill fort.  The not-so-dedicated may use the top of the parallel middle rampart.  At the time of writing (1993) the turf on these northern ramparts is in a state of flux.  Until 1986 the area was grazed hard and often, creating an extremely short turf but one that consisted of all the usual downland plants.  This created somewhat arid conditions in the summer but ideal conditions for the over-wintering immature stages of many butterflies.  After 1986 clumps of scrub were removed and areas of erosion were repaired.  Whilst the repairs were "making good", grazing was strictly limited and the growth became longer.  Grazing is now more widespread  again and the turf length is recovering.  This has now been relaxed, but few of the grazing stock actually find the herbage of interest.On reaching the north-west corner, those that started here can now make their way to Child Okeford for refreshments, whilst others, who started at Section 7, must now complete Sections 1 to 6 before returning to Stourpaine.