Food consumption of Chilocorus kuwamae Silvestri (Coccinellidae)

Abstract

Chilocorus kuwanae is the most important predator of Unaspis yanonensis in Japan. It can be reared readily by Chrysomphalus bifasciculatus infested on squashes in insectary. This experiment was carried out in order to know the feeding habits as fundamental knowledge on mass production of the Coccinellid for control of Unaspis yanonensis.
In the individual feeding tests, each instar larva and adult were kept separate in a plastic vial of 13mm. long and 18mm. in diameter stuck to the surface of squash with paraffin and covered with organdie. Number of Chrysomphalus bifasciculatus infested on the surface of squash in the vial was 30 of adults or 60 of the second instar larvae in one test.
Observation was made every day at the fixed time during period of each stage, but in another test it was continued from the first instar larva to pupation and on adult it was made during three days.
Adults of Chilocorus kuwanae used for this test were as follows; non-gravid adult female of 3 days after emergence, gravid female of 15 days after emergence and ovipositing female of 27 days after emergence.
The amount of food consumed by larvae increased with progress of larval instars; the fourth instar larva consumed 25.74 of the second instar larva of scale or 9.45 of adult scale per day and it is greater than the amount of food consumed by other instar larvae on both stages of the scale. Total food consumption at larval period is 330.58 of the second instar larva of the scale or 107 of adult scales.
Duration of each larval instar shortens when they consumed adult scales compared with the second instar larva of them; when they consumed adult scales, the duration of the first to the fourth instar are 3.55, 3.55, 4.00 and 7.00 days respectively and the total length of larval period is 18.10 days and when they consumed the second instar larva of the scale, the duration of the first to the fourth instar are 6.25, 5.00, 7.57 and 8.75 respectively and the total length of larval period is 27.57 days.
Food consumption by adult Chilocorus kuwanae is the greatest in gravid female and the amount per day is 19.66 of adult scale or 53.33 of the second instar larva of the scale. The consumption by adult male is smaller than by female.
From these results adult Chrysomphalus bifasciculatus seems to have better quality for development of Chilocorus kuwanae, therfore it will be better food for mass production of this Coccinellid. From the feeding capacity of larval period the maximum number of the Coccinel-lids which can be reared on a squash is estimated; about 300 of Coccinellids can be reared on a squash with surface of 960cm2, because about 33000 adults of the scale infest on this squash.