Contents Part I. Essex Field Club Transactions and reports Report of the Essex Field Club for 1997/98 ............................... 1 Income and expenditure account for 1997 ................................ 3 Balance sheet for 1997................................................ 4 Auditor's report for 1997 .............................................. 4 The 1998 Presidential Address: The geological history of the lower Thames in Essex - A review. Peter Allen............................. 5 From the Club's Recorders: Review of the Lepidoptera of Essex for the year 1997. Brian Goodey............ 23 Bats in Essex in 1997. John Dobson ...................................... 32 Essex mammals in 1997. John Wright..................................... 34 Dragonfly (Odonata) report for 1997. Ted Benton .......................... 36 Interesting Hymenoptera records for 1997-1998. P.R. Harvey................. 38 Some interesting spider records tor 1997 and 1998. P.R. Harvey............... 45 Part 2: Contributed papers Cetaceans stranded on the Essex coast. John Dobson......................... 47 New Charophyte (Stonewort) and Bryophyte Records. K.J. Adams ............ 55 The third Essex Flora and BSBI Atlas 2000 Projects: An historical perspective. K.J. Adams ............................ 57 The modern distribution of ants (Hymenoptera: Formicidae) in Essex with their regional rarity and threat status. P.R. Harvey ................... 61 Short Communications New protection for Fisher's Estuarine Moth. Chris Gibson .................... 22 Reed hover at Old Hall Marshes Nature Reserve. Terri Tarpey ................ 60 Instructions to Contributors 112