I have sowed pumpkin seeds of mahyco company. seeds are treated with tiram etc which was mentioned on packing box. Very next day i have seen that seeds are on top of soil with inside seed eaten completely leaving shell.
I noticed that its not ant activity. some insects which look are in ant size are doing this. tried sowing and putting polydol powder also but no use.
Thiram is a fungicide so it cannot keep away termites/ants etc.
Chimical method is mentioned by Nikhi.
Organic way you can coat gently with castor oil+Salt+Turmeric Powder.(this method is suggested by our forum member Gunda)
Or use 250gm of neem cake around the seed when you plant.