What to pay attention to when keeping ground beetles for breeding stock

When ground beetles (Eupolyphaga sinensis) are taken from the wild and switched to artificial rearing, there is the problem of keeping breeding stock. Although artificial rearing has not been carried out for long, because the issue of keeping breeding stock was not given attention in the early stage, problems of stock degeneration have also appeared, showing as deformed bodies, reduced egg production, weakened vitality, etc., so in the future when keeping breeding stock, the following issues must be given attention:

1) Selection of females. Breeding females kept for stock should be chosen as large in body size, oval, with a full abdomen, glossy, strong in activity, quick in movement, with a large food intake, and free of parasites and diseases. 2) Collection of wild breeding insects. After ground beetles have been artificially reared, stock sources kept at home for several generations already show degeneration. In order to improve the quality of the stock, some wild ground beetles can be collected as breeding stock, or wild males can be crossed with home-reared females. Collection of wild ground beetles is generally done from May to September. Take 1 basin, put roasted wheat bran inside, bury it in a place where wild ground beetles appear, to lure the wild ground beetles into the basin to eat; after they crawl down they cannot easily get up again, and they can then be captured. 3) Selection of breeding eggs. All the egg capsules laid by 1 egg-laying female differ in vitality because they were laid at different times. Under normal conditions, eggs laid by young and vigorous adults in July to August have a high hatching rate, and the hatched nymphs are robust and strong in vitality. Therefore, eggs laid during the peak egg-laying period are best kept as breeding eggs. Egg capsules shaped like bean pods, reddish-brown, glossy, with plump eggs, can be kept for stock; those with shrunken, damaged or moldy eggs are not suitable for keeping as stock. 4) The question of whether to keep or remove males. Male nymphs at the 8th instar can be picked out before they grow wings, either for medicinal use or as feed insects for centipedes, which both reduces feed and increases utilization. If they are to be used as breeding insects, they should no longer be removed, so as not to affect the fertilization rate of the eggs. In addition, males mature earlier than females and have shorter lifespans, so in production, the males in the same batch of breeding insects to be kept should be picked out and placed into a group of breeding females that hatched 3 to 5 months earlier than they did for mating; in this way the males can be fully utilized. Therefore, only by correctly distinguishing female from male nymphs before the males grow wings can the utilization of males be benefited. The characteristics of female and male nymphs are shown in Table 5. 5) Harvesting of ground beetles. If the purpose of rearing ground beetles is to use them as feed insects for centipedes, then ground beetle nymphs of different instars should be supplied according to the individual size of the centipedes. The harvesting method is the same as the method for collecting wild ground beetles, namely using an enamel basin with roasted wheat bran placed inside. Bury the enamel basin in a corner or at the edge of the rearing pond, with the upper rim of the enamel basin level with the ground. After ground beetles smell the wheat bran, they crawl toward the enamel basin holding the wheat bran; when they reach the edge of the basin and continue forward, they fall into the enamel basin, and because the enamel basin is slippery they cannot climb up again. After collecting the ground beetle nymphs, use sieves with different mesh sizes to sieve and grade them. Put the older ground beetle nymphs into larger-scale centipede rearing ponds, and put the younger ground beetle nymphs into smaller-scale centipede rearing ponds, to make it easier for the centipedes to prey on them.