Okay, giant millipedes? That's a lot of work I don't feel like doing. I did, however, add in trilobites and those vermin-diving dragonflies I promised:
[CREATURE:TRILOBITE_STL]
[NAME:trilobite:trilobites:trilobite]
[CASTE_NAME:trilobite:trilobites:trilobites]
[DESCRIPTION:Hardy, diverse organisms, found in varying forms across the oceans and rivers of the world.]
[CREATURE_TILE:172][COLOR:4:9:0]
[BODY:VERMIN_BODY_HLG]
[PREFSTRING:meatball-like characteristics]
[VERMIN_FISH][FISHITEM][IMMOBILE_LAND][VERMIN_NOTRAP][VERMIN_GROUNDER]
[UBIQUITOUS]
[MUNDANE][NOT_BUTCHERABLE]
[BIOME:ANY_OCEAN]
[BIOME:ANY_LAKE]
[BIOME:ANY_RIVER][POPULATION_NUMBER:1000:1500]
[BODY_DETAIL_PLAN:LIGHT_CHITIN_MATERIALS_STL]
[BODY_DETAIL_PLAN:LIGHT_CHITIN_TISSUES_STL]
[BODY_DETAIL_PLAN:INSECT_LAYERS_STL]
[CREATURE_CLASS:ALL][CREATURE_CLASS:INVERTEBRATE][CREATURE_CLASS:ARTHROPOD]
[BODY_SIZE:70]
[NO_DRINK]
[SWIMS_INNATE][SWIM_SPEED:800] They're like rocket-propelled meatballs!
[CASTE:FEMALE]
[FEMALE]
[CASTE:MALE]
[MALE]
[CREATURE:AESHNIDA_STL]
[NAME:aeshnida:aeshnidae:aeshnida]
[CASTE_NAME:aeshnida:aeshnidae:aeshnida]
[CREATURE_TILE:'d'][COLOR:2:0:0]
[DESCRIPTION:A large dragonfly that darts through the air with precision and inborn skill as it searches for prey.]
[PREFSTRING:precise movements]
[BODY:BASIC_INSECT_STL:ANTENNAE_STL:4WINGS_STL:MANDIBLES_STL:2EYES_STL:BOOK_LUNGS_STL:BRAIN_STL:HEART_ABDOMEN_STL]
[BODY_SIZE:4600]
[BODY_SIZE:0:0:500]
[BODY_SIZE:1:0:2000]
[BODY_SIZE:2:180:4600]
[CHILD:2][PET][PETVALUE:100]
[BENIGN]
[BODY_DETAIL_PLAN:LIGHT_CHITIN_MATERIALS_STL]
[BODY_DETAIL_PLAN:LIGHT_CHITIN_TISSUES_STL]
[BODY_DETAIL_PLAN:INSECT_LAYERS_STL]
[BODY_DETAIL_PLAN:INSECT_POSITIONS_STL]
[APPLY_CREATURE_VARIATION:BITE_MANDIBLE_STL]
[APPLY_CREATURE_VARIATION:IS_INSECT_STL]
[APPLY_CREATURE_VARIATION:APPEARANCE_VARIABILITY_BODYSIZE_HLG]
[APPLY_CREATURE_VARIATION:APPEARANCE_VARIABILITY_INSECT_EYES_STL]
[APPLY_CREATURE_VARIATION:APPEARANCE_VARIABILITY_DRAGONFLY_COLOR_STL]
[DIVE_HUNTS_VERMIN]
[FLIER]
[LARGE_ROAMING]
[POPULATION_NUMBER:900:1100][CLUSTER_NUMBER:3:5][LOOSE_CLUSTERS]
[BIOME:ANY_TROPICAL]
[BIOME:ANY_SAVANNA]
[CASTE:FEMALE]
[FEMALE]
[CASTE:MALE]
[MALE]
So, some benign, wimpy bugs to fool the halflings into thinking that not everything wants them dead. The trilobites should also make river fishing possible, I think, or at least profitable, since nothing lived there before to my knowledge.
[PLANT:UMBRELLA_TREE_STL]
[NAME:umbrella tree]
[NAME_PLURAL:umbrella trees]
[ADJ:umbrellawood]
[USE_MATERIAL_TEMPLATE:STRUCTURE:PLANT_STRUCTURE_HLG]
[BASIC_MAT:LOCAL_PLANT_MAT:STRUCTURE]
[PREFSTRING:shady canopy]
[USE_MATERIAL_TEMPLATE:WOOD:PLANT_STRUCTURE_HLG]
[STATE_NAME:ALL_SOLID:umbrella wood]
[STATE_ADJ:ALL_SOLID:umbrella wood]
[PREFIX:NONE]
[STATE_COLOR:ALL_SOLID:BROWN]
[DISPLAY_COLOR:6:0:0]
[WOOD]
[TREE:LOCAL_PLANT_MAT:WOOD]
[WET][DRY]
[BIOME:ANY_SAVANNA]
[TREE_TILE:226]
[TREE_COLOR:2:0:0]
[SAPLING_COLOR:2:0:0]
[PLANT:CINDERWOOD_TREE_STL]
[NAME:cinderwood tree]
[NAME_PLURAL:cinderwood trees]
[ADJ:cinderwood]
[USE_MATERIAL_TEMPLATE:STRUCTURE:PLANT_STRUCTURE_HLG]
[BASIC_MAT:LOCAL_PLANT_MAT:STRUCTURE]
[PREFSTRING:volatility][PREFSTRING:choking shroud of smoke]
[USE_MATERIAL_TEMPLATE:WOOD:PLANT_STRUCTURE_HLG]
[STATE_NAME:ALL_SOLID:cinderwood]
[STATE_ADJ:ALL_SOLID:cinderwood]
[PREFIX:NONE]
[STATE_COLOR:ALL_SOLID:RUST]
[DISPLAY_COLOR:4:0:0]
[HEATDAM_POINT:NONE] "Like eternal columns of the blackest smoke they stand, grim sentinels holding vigil o'er the endless sand..."
[IGNITE_POINT:9000]
[WOOD]
[TREE:LOCAL_PLANT_MAT:WOOD]
[DRY]
[BIOME:ANY_DESERT]
[TREE_TILE:198]
[TREE_COLOR:4:0:0]
[SAPLING_COLOR:4:0:0]
And a few more trees, one usable, the other basically a flaming stick that never burns away and chokes its host desert in smoke.