Rearing Methods and Technical Key Points for Ground Beetles (Eupolyphaga)

(1) Rearing equipment can be designed according to the scale and purpose of rearing. Here we only introduce the rearing equipment used to provide a source of medicinal insects. ① Insect sieves: their purpose is to separate nymphs of different instars, adults and oothecae by sieving within a certain period, and then rear them separately and isolate the medicinal insect bodies. The sieve apertures are divided into 5 specifications: 2-mesh sieve: used when separating out adults. 4-mesh sieve: used when separating out 7th-8th instar nymphs. 6-mesh sieve: used when separating out oothecae and insect feces. 12-mesh sieve: used when separating out 1st-2nd instar nymphs. 17-mesh sieve: used when separating out newly hatched nymphs and clearing out the parasitic natural enemy Tyrophagus mites. ② Grid-type rearing pits and semi-underground rearing ponds: the grid-type rearing pit makes use of old houses, temporarily unused livestock sheds with roofs and enclosing walls, latrines, etc., by digging a pit about 67 cm deep, 70-100 cm wide and of unlimited length underground (this can be determined according to the rearing quantity and the actual conditions inside the building). Level and compact the pit bottom, and build up and plaster the surrounding walls with cement to make them smooth. It is even better to affix a 3-7 cm wide strip of glass at the pit opening above the pit wall to prevent the ground beetles from escaping. Inside the pit, use thin cement boards or glass to divide it into several small cells; the size of each small cell should be standardized so as to calculate the stocking quantity of nymphs of different instars and to calculate the yield per unit area. Place 20-27 cm of rearing soil into the pit, fit a fairly tight wooden cover around the pit opening, leave ventilation holes fitted with window screening, and then separately place in adults or nymphs of different instars. Rearing in separate cells facilitates management and feeding. Because most of this kind of rearing pit extends below the ground surface, the temperature inside the pit in winter is higher than the ground surface and in summer lower than the ground surface, which allows the ground beetles to be less affected by seasonal changes, is beneficial to their growth and development, and can increase the survival rate. The structure of a semi-underground rearing pond is similar to the grid-type rearing pit, except that half the depth of the pond is buried underground and the other half rises above the ground; the pond is no longer divided into cells, the pond is 2 m long and 1.5 wide, and besides ventilation holes the pond cover must also have a double-layer screen door for convenient management and operation. Semi-underground rearing ponds are suitable for rearing adults, carrying out mass breeding and obtaining insect bodies for medicinal use.

(2) Preparation and treatment of rearing soil. The ground beetle is an insect that hides by day and comes out at night, retreating into the soil to rest during the day, and it likes to seek food in the soil or on the soil surface. Therefore, soil is the micro-environment of this kind of insect. The quality of the soil and the combination of the substances it contains are directly related to the survival, growth and development of the ground beetle. ① Soil quality and water content: the requirements for choosing rearing soil vary from place to place and should be adjusted according to specific conditions, such as vegetable garden soil, garbage soil, ditch mud, stove-foot soil, sand-clay mixed soil, while mixing in an appropriate amount (20%-30%) of fermented chicken manure, pig manure, horse manure, cinder ash or rice husk ash. No matter which kind of soil is chosen, after mixing it should be loose in texture, rich in nutrients and moderate in dryness and moisture, able to be formed into a ball when squeezed in the hand and to crumble apart when the hand is opened. If the water content is measured, it should be 15%-20%. Such soil quality makes it easy for the ground beetle to hide, burrow in or crawl out, and to move about freely seeking food and looking for a mate. ② Treatment of rearing soil: before the rearing soil is put into the pit or pond, it must be exposed to sunlight, sterilized and freed of insects, and sieved to remove impurities as well as bricks and stones. All factors unfavorable to the life of the ground beetle should be eliminated in advance as far as possible. The thickness of the rearing soil laid in the pond must differ according to different instars or adult stages, and the soil thickness must also differ for different densities in the same pond and in different seasons. Experience has shown that the thickness of the rearing soil should be 7-10 cm for 1st-4th instar nymphs; 16-20 cm for 5th-8th instar insects; and 20-26 cm for 9th-11th instar insects and adults. In the same pond, where the insect population density is high the soil should be thicker, and where the density is low the soil should be shallower; in summer the soil should be thinner and in winter thicker; for rearing breeding insects the soil layer should be thicker than for rearing medicinal insect bodies, so as to help the mating and egg-laying process be less disturbed.

(3) Selection and feeding of feed. The ground beetle is an omnivorous insect. But judging from the feeding physiology of insects and their different degrees of greed for food, any omnivorous insect also has the range of food it most likes to eat. Under artificially controlled rearing conditions, whether the selected and combined feed is appropriate is directly related to the success or failure of rearing and the size of the harvest. ① Types of feed: generally they can be divided into 3 kinds of feed of different nature: Plant-based feed: includes wheat bran, rice bran, oil cake meal, powder residue, broken rice, corn and other miscellaneous grain powders. These are stir-fried until a fragrant smell overflows, then spread out to cool before feeding. Animal-based feed: the leftover pig, cattle, chicken, duck, fish and other scraps from restaurants can all be used as feed for them to eat, but they must not be spoiled or deteriorated, in case the ground beetles become diseased and die. If conditions permit, they can be processed into a fluffy mixture of bone and meat and kept refrigerated. @#@254@#@, crickets, locusts, moths and other small insects, after being killed, can be thrown in directly for them to eat. Earthworms can also be artificially reared (apart from being used as medicine) to feed the ground beetles, which are most greedy for them. Green feed: this is food that must be combined in rearing ground beetles. Leaves of green vegetables, cabbage, lettuce, amaranth, as well as sesame, broad bean, peanut, sweet potato, etc., and pumpkin, loofah flowers and fruits can all be fed. Melon and fruit rind and pulp and sweet potato, etc., cut into pieces, are even more preferred for feeding. The green feed fed should be kept fresh and clean. Special care must be taken not to pick green feed that has been sprayed with insecticide, to prevent the ground beetles from being poisoned and dying. ② Combined feeding: in the high-temperature seasons of summer and autumn, green feed must be added 1-2 times every day, preferably placed in the morning and kept fresh. To increase nutrition, pumpkin flowers and loofah flowers are indispensable. As for the number of feedings and the feeding amount per day, one should grasp that in low-temperature months feed once every other day, and in high-temperature months feed 1-2 times every day. The feeding amount should match the insect population density in the pit or pond. After each feeding, observe whether the feed is left over or lacking; in principle, grasp that the concentrated feed is eaten up and the green feed is left over, so as to let the insects eat their fill while avoiding unnecessary waste and surplus residual feed attracting parasites and plant-feeding mites. Before and after the ground beetle molts its food intake decreases and it should be fed less; during molting it stops feeding, so do not feed. This is when many insect skins are found on the surface of the rearing soil, or many individuals with relatively light body color are seen.

(4) Scientific management. In rearing ground beetles under artificial conditions, scientific management is the key to success or failure, and it is relatively complex and meticulous work that should be done conscientiously.

① Collecting eggs and egg hatching: after mating, the female begins to lay eggs after about 1 week. The egg-laying period can last from early May to November, with June to September being the peak egg-laying period. The ootheca is laid outside the body and is dragged at the tail end for a period before it drops onto the soil surface or sticks to the edge of the rearing pond. Because ground beetles when reared in groups have the phenomenon of eating oothecae, the ootheca sacs can be moved out and placed in another small rearing container to be hatched in isolation. When collecting oothecae, first use a 2-mesh sieve to separate out the adults, then use a 6-mesh sieve to separate out the oothecae. The interval between each egg collection should not be too short; collecting eggs too many times is unfavorable to the development of the breeding insects. But if the interval is too long, the oothecae will also be worn and disturbed by the crawling of adults or the turning of the surface soil, affecting the hatching rate of the eggs. Under normal circumstances, collecting eggs about every 15 days is more suitable.

② Removing males and selecting the superior: this is to eliminate part of the male insects that have hatched naturally and have not yet developed to maturity. Too many males not only consume feed and occupy rearing area, but more importantly males are not suitable as raw material for Chinese medicine. Under natural conditions, the ratio of females to males is about 13:5. Under artificial rearing conditions, as long as there are 15% lively and robust males, the mating needs of group rearing can be fully met, without affecting egg fertilization and hatching. The work of removing males can be carried out once the nymphs have grown and developed to the 6th instar. The main difference between male and female nymphs lies in the shape of the dorsal plates of the second and third thoracic segments and the degree of slant of the posterior corner of their outer edge; the slant angle of male nymphs is large and that of females is small. The above characteristics are obvious in species with male-female dimorphism, and not very prominent in species of the same form. The work of removing males can be carried out together with selecting the superior and eliminating the inferior. Retaining high-quality breeding insects is one of the keys to obtaining high yield and high economic benefit. When removing males, one should retain the robust, lively, large-bodied, brightly colored individuals with complete limbs from the same batch hatched and of the same age (if unhealthy females are found, they should also be removed at the same time).

③ Rearing by grades: this is to rear insects of different instars or of close individual size separately in different rearing ponds, so that their degree of development basically reaches uniformity, which facilitates feeding and adding feed as appropriate, management and harvesting. Generally they can be divided into 4 grades: the 1st-6th instar grade, the 7th-8th instar grade, the 9th-11th instar grade, and the adult grade. When first rearing, it is relatively difficult to distinguish the instar of nymphs, so they can be graded according to insect body size, such as the sesame type (nymphs that have developed to 1-2 months after hatching from the egg); the soybean type (nymphs that have developed to 3-4 months); the broad bean type (nymphs that have developed to 5-6 months); the thumb type (body as large as a thumb nail, that is, adults).