STUDIES ON PERILLUS BIOCULATUS FAB. 63 
Feeding Habits of Nymphs 
During the first nymphal instar the bugs do not require animal 
food. Several groups of newly hatched nymphs have been watched, 
yet it seems rather doubtful if they even take sap from the leaf where 
they remain quietly huddled. In this stage the nymphs rarely move 
about, but spend the whole time in a closely formed group, apparently 
awaiting the second day, when they molt and start in search of food. 
During the second instar the nymphs feed largely on eggs or newly 
hatched larvae of the potato beetle; but when these are not available 
they may be observed attacking larger grubs, or joining in the feast 
provided by an older nymph or adult bug. When a nymph success- 
fully attacks a grub, it is usually joined by two or three of its brothers, 
for increased numbers help materially in rendering the prey helpless. 
Beginning with the third instar, individual nymphs will attack all 
stages of the potato beetle grubs, and during the fourth and fifth 
instars the same nymphs will attack mature beetles when the grubs 
are not available. 
The writer has reared Perillus from egg to adult on nothing but 
mature beetles, but in this case the beetles were always rendered 
helpless for the beneht of nymphs in the second and third instars. 
More labor is necessary in rearing Perillus on beetles alone that when 
grubs are available, yet it has been done in order to rear a fall gen- 
eration of bugs after the potato beetle grubs have disappeared. By 
this method of rearing, Perillus could no doubt be kept active and 
breeding during the winter months if proper greenhouse facilities were 
available. 
To determine the amount of food consumed by individual bugs, 
and thereby to estimate the economic value of Perillus, a good series 
of bugs has been reared singly in jars and a record kept of the food 
consumed. The following is an average for the food consumed during 
the different stages of development: Stage I: no food, or possibly sap 
from potato leaf; Stage II: 36 eggs of potato beetle; Stage III: 8 large 
grubs; Stage IV: 12 grubs or beetles; Stage V: 14 grubs or beetles. 
This gives a total of 36 eggs and 34 grubs or beetles, consumed by one 
Perillus nymph during its immature stages. Within six weeks one 
adult Perillus consumed 84 beetles and grubs, which combined with 
the average amount of food taken by a nymph during its development, 
gives a total of 36 eggs and 118 grubs and beetles destroyed by one 
Perillus. Under field conditions both nymphs and adults undoubtedly 
destroy many more eggs than were fed in the above experiments. 
