STUDIES ON PERILLUS BIOCULATUS FAB. 
“NI 
On 
must be very careful about the selection of food for Perillus, and 
never select grubs or beetles from vines which have been sprayed with 
arsenicals. Perillus is apparently more sensitive to arsenic poisoning 
than are the potato beetles, for one can go among the sprayed vines 
and select grubs which appear healthy, but when fed to Perillus the 
bugs die very shortly. This has been tested so many times that there 
is no doubt in the writer’s mind that spraying for potato beetles 
will also result in the death of nearly all Perillus in the field sprayed. 
It is unfortunate that this is true, for otherwise Perillus might be 
able to destroy all the beetles not killed by the spray. From this it 
may be concluded that spraying for the potato beetle is also one of 
the factors which serves to check the increase of Perillus in commer- 
cial potato fields. 
Perillus would prove more beneficial in the potato fields if they 
were not so economical in their feeding habits. Unfortunately they 
rarely waste food by giving up a victim that has been sucked to the 
point of death. Once the potato grub or beetle has been overpowered, 
Perillus feeds on the victim until it is sucked dry. Then again, when 
one Perillus seizes a victim in the vicinity of other bugs, the latter 
will join in sharing the food rather than each taking the trouble io 
kill a different victim. Were Perillus as bloodthirsty as Podisus macu- 
liventris Say, the species would be more efficient as a beneficial insect 
in the control of the potato beetle. 
The average amount of food consumed by an individual Perillus 
has been indicated above under a discussion of the nymphs. It was 
found that one nymph consumed 36 eggs and 34 grubs or beetles be- 
fore attaining the adult stage. One adult Perillus destroyed 84 beetles 
and grubs during a life of six weeks, which is not an uncommon period 
of activity. Under field conditions the bugs would doubtless destroy 
many more eggs of the potato beetle than were fed in the above 
experiments. 
Kinds of Insects Fed Upon by Perillus 
There are a few records of Perillus bioculatus feeding on insects 
other than the potato beetle. Nash (1912) in speaking of this pre- 
daceous bug says: “Early in August I found several of these bugs 
in the nymph stage feeding on Tussock moth larvae.” Marsh (1913) 
says that “Perilloides bioculata Fab. a pentatomid, was frequently 
found stabbing the partly grown Mamestra larvae.” The writer‘ has 
placed a larva of Mamestra picta in a cage with several hungry speci- 
mens of Perillus bioculatus and both nymphs and adults fed unon it. 
In 1913 and 1914, while breeding for color inheritance in Perillus, the 
