on the larvae of Museidae. 19 
their environment, an adaptation which, in a certain measure, destroys 
the parallelism which we naturally expect to exist between the syste- 
matic characters of larva and imago. Such apparent want of parallelism 
has been observed in the order of Diptera before, but an abundance 
of new facts are found in Mr. Portchinski’s paper. Distantly related 
species, belonging to different genera, issue from larvae almost undistin- 
guishable from each other. And again closely related and almost 
undistinguishable imago’s, species of the same genus, differ in their 
oviposition (size and number of eggs), and their larvae follow a dif- 
ferent law of development (as to the degree of maturity the larva 
reaches within the body of the mother and the number of stages 
of development it passes through). In one case even (Musca corvina) 
larvae of the same species were found to have a different mode of 
development in northern and in southern regions. 
The following abstract reproduces the facts and merely conden- 
ses the statements. We begin with the carnivorous lagvaeı). 
Calliphora erythrocephala (the blue-bottle fly). Its development 
has been thoroughly investigated in the well-known work of Mr. 
Weissmann. — It lays its eggs on meat and on dead animals. The 
elongated eggs are remarkably small, only about one millimeter long. 
Mr. Portchinski found as many as 450 to 600 in the body of a 
single fly; that is 225 to 300 in each of the ovaries, counting the 
last row of ripe eggs only, as it is very probable that the undeve- 
loped eggs of the second and following rows never come to maturity. 
About 24 hours after the egg is laid, the larva is hatched, in the 
first stage of its existence, easily distinguished by the shape of the 
posterior stigmatic horny plates; they are exceedingly small, and 
have a single, characteristic heart-shaped breathing-fissure. In 
the second stage, the stigmatic plates are much larger, each 
with a pair of straight, subparallel fissures in the middle. In the 
third and last stage before becoming a pupa, the larva has still 
larger stigmatic plates, each with three subparallel breathing-fissures. 
(Fig. 1. I quote the figures of Mr. Portchinski’s original article.) 
When the larva is about to pass from the second to the third stage, 
the stigmatic plates of the third stage are distinctly visible through 
the integuments of the larva, behind those of the second stage; the 
‚larva seems then to have two pairs of posterior stigmata. 
1) It must be borne in mind that most of the observations of 
Mr. P. were made in St. Petersburgh and environs; those made in the 
south of Russia are specially mentioned. 
DI 
