In the Navy [Japanese] a seaman who has captured 300 cockroaches will be granted one day special shore leave. They call it "shore leave for cockroaches." The purpose is to promote extermination of cockroaches in a warship because, on the one hand, any warship suffers from numerous cockroaches, and, on the other hand, any seaman likes shore leave.... The formalities for a shore leave for cockroaches are as follows. A seaman keeps cockroaches which he captured (mainly _B. germanica_, because _P. americana_ and _P. australasiae_ are seldom found in Japan) in a bottle or in a bag until the number reaches 300. Then he brings them to the deck officer to get the confirmation that he has actually captured more than 300 cockroaches. If the deck officer confirms it, the seaman goes to a cabin where a petty officer reports that the deck officer confirmed the number of cockroaches. The petty officer signs the seaman's name, name of division, rank, and date to be on shore leave in the log book for cockroach shore leaves. The petty officer brings the log book again to the deck officer to get his approval and then goes to the commander for the final approval. In the Navy, they have another special shore leave for rats. In this system, a seaman gets one day shore leave for one rat. The formalities for the latter are the same as for the former, and there is a log book for the rat shore leave in the petty officer's quarters. The author took advantage of these systems frequently. SONAN (1924) Little is known of the effects of predatism and parasitism on natural populations of cockroaches. Many statements in the literature are very general; yet there are a few data on egg parasites (e.g., _Tetrastichus hagenowii_) which suggest that, in the absence of parasites, populations of domestic cockroaches might be much larger than they are in certain areas. We have summarized the literature on natural control and also that on the use by man of predators and parasites in the biological control of cockroaches. However, because of the paucity of information, we have been unable to evaluate the effectiveness of biological control in reducing the numbers of pest cockroaches. This is an area that might reward further investigation. INVERTEBRATES _Scorpions._--In Puerto Rico, cockroaches are probably the principal food of the scorpions which live in old houses, on tree trunks, etc. (Seín, 1923). The staple diet of scorpions in Arizona is the small cockroach commonly known as the water bug (Stahnke, 1949); in the part of Arizona where he resides, Stahnke (personal communication, 1953) says that the "water-bug" is most generally _Supella supellectilium_ although _Blattella germanica_ is also found, but less abundantly.