Laboratory Studies on the Egg of the Blowfly Lucilia Sericata (MG.)

Abstract

The chorion of the Lucilia sericata egg is shown to be composed of two main layers, both of protein; the outer can be tanned by p-benzoquinone, but the inner is apparently already tanned. The chorion and the chorionic vitelline membrane are both lipidized shortly before the egg is laid. This makes both structures more rigid, but does not waterproof the shell. After the lipidization process is completed, a lipoid waterproofing layer is laid down by the öocyte, between the chorion and the chorionic vitelline membrane. This waterproofing layer has a critical temperature in the region of 38° C., and can be damaged by an abrasive dust, emulsified by the detergent I.C.I. C09993, and removed by chloroform at 3° C. in 12 hr. The minimum humidity for development of L. sericata eggs at 37° C. has been found to be 50 % R.H. At 1-2° C. above this temperature eggs require about 80 % R.H. to complete development. Eggs at 37° C. can withstand fairly long periods of humidities below 50 % R.H., provided they have not been previously incubated in saturated air at that temperature. The latter treatment, even if continued for only 30 min., makes eggs far more susceptible to desiccation when infsequently incubated at a low humidity. Fully developed larvae can survive imprisonment within the egg-shell for about 3 hr. at 37° C.