diff --git a/agent.cc b/agent.cc
index a595140..fb71fbc 100644
--- a/agent.cc
+++ b/agent.cc
@@ -143,4 +143,30 @@ agent::~agent()
 		conn->cancel();
 		conn = NULL;
 	}
-};
+}
+
+
+static void
+spawn_herb(class tile &t)
+{
+	if (t.agent)
+		return;
+	class herb *h = new class herb(agent_id++, t.map);
+	agents.push_back(h);
+	h->spawn_at(t);
+}
+
+void
+herb::on_tick(void)
+{
+	agent::on_tick();
+
+	assert(tile);
+	if (energy > 4 * world::herb_energy) {
+		spawn_herb(tile->tile_in_dir(1, 0));
+		spawn_herb(tile->tile_in_dir(0, 1));
+		spawn_herb(tile->tile_in_dir(-1, 0));
+		spawn_herb(tile->tile_in_dir(0, -1));
+		die();
+	}
+}
diff --git a/agent.h b/agent.h
index d080b44..968ec27 100644
--- a/agent.h
+++ b/agent.h
@@ -42,7 +42,7 @@ public:
 	void die(void);
 
 	void on_action_takes(void);
-	void on_tick(void);
+	virtual void on_tick(void);
 	void on_senses_update(void);
 
 	~agent();
@@ -58,6 +58,8 @@ public:
 		attr.attack = 0;
 		attr.defense = 0;
 	}
+
+	void on_tick(void);
 };
 
 #endif
diff --git a/main.cc b/main.cc
index f157c8c..95eaf37 100644
--- a/main.cc
+++ b/main.cc
@@ -19,6 +19,24 @@
 
 int tick_id = 0;
 
+int agent_id = 0;
+std::list<class agent *> agents;
+
+static void
+drop_agents(void)
+{
+	for (std::list<class agent *>::iterator agent = agents.begin(); agent != agents.end(); agent++)
+	{
+next_agent:
+		if (((*agent)->conn && (*agent)->conn->error) || (*agent)->dead) {
+			delete *agent;
+			agent = agents.erase(agent);
+			if (agent != agents.end())
+				goto next_agent;
+		}
+	}
+}
+
 int
 main(int argc, char *argv[])
 {
@@ -42,13 +60,10 @@ main(int argc, char *argv[])
 	int flags = fcntl(lfd, F_GETFL, 0);
 	fcntl(lfd, F_SETFL, flags | O_NONBLOCK);
 
-	std::list<class agent *> agents;
-	int aid = 0;
-
 	/* Spawn herbs. */
 
 	for (int i = 0; i < herbs; i++) {
-		class agent *a = new class herb(aid++, map);
+		class agent *a = new class herb(agent_id++, map);
 		agents.push_back(a);
 		a->spawn();
 	}
@@ -60,23 +75,14 @@ main(int argc, char *argv[])
 
 		/* Drop disconnected agents. */
 
-		for (std::list<class agent *>::iterator agent = agents.begin(); agent != agents.end(); agent++)
-		{
-next_agent:
-			if ((*agent)->conn && (*agent)->conn->error) {
-				delete *agent;
-				agent = agents.erase(agent);
-				if (agent != agents.end())
-					goto next_agent;
-			}
-		}
+		drop_agents();
 
 		/* Accept new agents. */
 
 		int cfd = accept(lfd, NULL, NULL);
 		if (cfd >= 0) {
 			class connection *conn = new class connection(cfd);
-			class agent *a = new class agent(aid++, conn, map);
+			class agent *a = new class agent(agent_id++, conn, map);
 			agents.push_back(a);
 		}
 
@@ -90,6 +96,7 @@ next_agent:
 		map.on_tick();
 		for (std::list<class agent *>::iterator agent = agents.begin(); agent != agents.end(); agent++)
 			(*agent)->on_tick();
+		drop_agents(); /* Some agents might have died. */
 
 		/* Update agents' senses. */
 
diff --git a/main.h b/main.h
index 487982c..be92079 100644
--- a/main.h
+++ b/main.h
@@ -1,6 +1,12 @@
 #ifndef BRMLIFE__MAIN_H
 #define BRMLIFE__MAIN_H
 
+#include <list>
+
+class agent;
+
+extern int agent_id;
 extern int tick_id;
+extern std::list<class agent *> agents;
 
 #endif
diff --git a/map.cc b/map.cc
index 0a9c392..681b5c0 100644
--- a/map.cc
+++ b/map.cc
@@ -4,6 +4,7 @@
 #include <iostream>
 
 #include "agent.h"
+#include "main.h"
 #include "map.h"
 
 bool
@@ -24,6 +25,26 @@ tile::on_agent_leave(class agent &a)
 void
 tile::on_tick(void)
 {
+	int herbs = 0;
+	herbs += tile_in_dir(1, 0).herb_here();
+	herbs += tile_in_dir(0, 1).herb_here();
+	herbs += tile_in_dir(-1, 0).herb_here();
+	herbs += tile_in_dir(0, -1).herb_here();
+	herbs += herb_here();
+
+	if (herbs) {
+		if (herb_here()) { agent->chenergy(world::soil_energy / herbs); }
+		if (tile_in_dir(1, 0).herb_here()) { tile_in_dir(1, 0).agent->chenergy(world::soil_energy / herbs); }
+		if (tile_in_dir(0, 1).herb_here()) { tile_in_dir(0, 1).agent->chenergy(world::soil_energy / herbs); }
+		if (tile_in_dir(-1, 0).herb_here()) { tile_in_dir(-1, 0).agent->chenergy(world::soil_energy / herbs); }
+		if (tile_in_dir(0, -1).herb_here()) { tile_in_dir(0, -1).agent->chenergy(world::soil_energy / herbs); }
+	}
+}
+
+bool
+tile::herb_here(void)
+{
+	return agent && (dynamic_cast<herb *> (agent)) != NULL;
 }
 
 char
diff --git a/map.h b/map.h
index e80e27a..9f7027e 100644
--- a/map.h
+++ b/map.h
@@ -19,6 +19,7 @@ public:
 	char *str(void);
 
 	class tile &tile_in_dir(int dir_x, int dir_y);
+	bool herb_here(void);
 
 	virtual bool on_agent_enter(class agent &);
 	virtual void on_agent_leave(class agent &);
diff --git a/world.h b/world.h
index daf8419..1ca46a0 100644
--- a/world.h
+++ b/world.h
@@ -3,7 +3,7 @@
 
 struct world {
 	const static int newborn_energy = 5000;
-	const static int herb_energy = 1500;
+	const static int herb_energy = 1000;
 
 	const static int move_cost = -50;
 	const static int attack_cost = -400;
@@ -13,12 +13,13 @@ struct world {
 	const static int attack_idle_cost = -15; /* ... * attr.attack */
 	const static int defense_idle_cost = -15; /* ... * attr.defense */
 	const static int sun_energy = 10;
+	const static int soil_energy = 10; /* ... times five for lone herbs, times one for dense forests */
 
 	const static int dead_body_energy = 2000;
 	const static double dead_body_energy_carryover = 0.5;
 	const static int dead_decay = -10;
 
-	const static int herb_rate = 20; /* one herb per herb_rate tiles */
+	const static int herb_rate = 15; /* initially, one herb per herb_rate tiles */
 };
 
 #endif