My first positive experience with blowfly larvae (called by anglers "white worms") I had it about 20 years ago. During the fishing competition, I was given a place on the pier, known for its unfavorable position and when fishing for small hurdles, I consoled myself with warm sun rays. The white worms in my bait box must have felt similar. Many of them began to turn into chrysalises. Throwing them into the water with the groundbait, I came up with the idea of using them as bait.
Without much thought, I placed one pupa and one larva on the hook, and then only two chrysalises. After some time I caught two bigger hurdles first, then one by one, six large bream, I lost a carp while hauling in and became a winner. Since then, the pupae have been an important bait for me for white fish. This bait, unlike mobile larvae, has "selective" properties, because if it is accepted by the fish once, this attracts mostly larger specimens than the larvae themselves. Nęcąc cocoon, fish can get used to this bait by chrysalises. Here, too, pupae have a great advantage over mobile larvae, because they lie quietly at the bottom and do not hide.
In the course of development of the larvae, their specific mass decreases, so that there is always some steam in a portion, which do not sink. By staying afloat, they lure fish from further distances to our fishery. It is important though, so that the majority of the groundbait will always sink to the bottom, because if all of them go away, the fish will follow them. How we see, white worms should be used at the appropriate stage of their development, and that requires preparation. To begin with, we discard the dead, be pupated already larvae, and put the rest flat, a vessel filled with sawdust and put it in the cellar. Only in cold and dark conditions does the development of the larvae take place slowly enough. Fresh worms (larvae) can be recognized by a black spot under the skin, which is slowly fading away. At the time, when it becomes invisible, they are found shortly before passing into the pupal stage. Later, an adult fly will develop from the chrysalis inside the cocoon. After the appearance of the first pupae, I pass the worms through a special sieve. The larvae go downstairs, and only the chrysalises remain in the strainer. The development of the larvae must now be stopped. For this purpose, they can be stored in the refrigerator, in a vessel of water. Like this with a constant water change, they will survive approx 3 days.
A much better way to store the larvae is to put them in a refrigerator in a sealed foil bag. Well chilled and out of air, they will survive there for up to a week. Because the larvae never transform simultaneously, they should be "strained" several times a day. However, this process should be complete after two to three days. Above the water, I add water to the container with the larvae, to prevent their further development. Only light brown to brown sinking larvae are suitable for baiting. Not sinking, finally (pupae), crumple and mix with groundbait. English white fish specialists appreciate this type of groundbait very much. In addition, I also attract larvae without any other additives (throw with a slingshot). I use the most delicate sets, little lead and 1-2 worms on the hook, therefore they sink as slowly in the water as the groundbait itself. To be caught on the ground, with a feeder for baiting with a "TV" or in your favorite system with a float, our larvae and pupae are surely an excellent bait for large roaches, bream and chubs.