Further studies on the multiple effects of carbon dioxide anesthesia in the German cockroach, Blattella germanica.

Effects of repeated carbon dioxide anesthesia during particular instars on the number of molts, larval duration and the body size of resulting adults were investigated. Concentration of carbon dioxide administered was 70%, and each anesthesia lasted for 5 min. Anesthesia was repeated four times during a particular instar. Anesthesia administered during the 1st, 2nd, or 3rd instar increased the number of instars required to reach maturity. When larvae were anesthetized during both the 1st and 2nd instar, the number of instars was greatly increased. However, anesthesia during the 4th instar scarcely influenced the number of instars. On the other hand, repeated anesthesia prolonged larval duration whenever administered from the 1st instar through the 4th. The body size of resulting adults remained almost the same as that for controls after the repeated carbon dioxide anesthesia during larval life. Detailed analyses of adult sizes, however, revealed that tibia length was more affected with the gas than femur length. The ratio of tibia length to femur length was also influenced by the experience of extra molt(s).