1923 ] Occurrence, Life-Cycle, and Maintenance of Miastor 97 
a suitable growth is attained. The embryos seem to be suitably 
developed, and are usually active for several days previous 
to their escape. At the time of escape, the larva, while not full 
grown, is well formed, active, and capable of continuing its 
existence. The time required for a typical psedogenetic gen- 
eration is about two weeks, though the period varies with in- 
divuals and environmental conditions. White paedogenetic 
larvae produce four to ten or more embryos. 
Polymorphism in Miastor Larvce, 
In all species of Miastor larvae, which I have observed, there 
occur three distinct larval forms. Two are paedogenetic: viz. 
white and yellow paedogenetic larvae, while the third is 
incapable of paedogenetic reproduction; it is the pupa-larva. 
(1) Typical white pcedogenetic larvae. 
The body of the larva contains fourteen segments. In the first 
or head-segment are the mouth opening and two antennae. 
The mouth parts are arranged for sucking. The second and 
third segments contain the optic ganglia, and the third segment 
two eyes. In typical paedogenetic larvae the eyes usually touch 
each other at their convex surfaces. The brain is in the fourth 
and fifth segments. Dorsal and partially posterior to it is the 
brain fat body. The salivary glands are in the fifth and sixth 
segments on either side of the oesophagus, their ducts opening 
in the mouth cavity. The oesophagus extends posteriorly from 
the mouth and opens into the intestine in the fifth segment. In 
this region the intestine enlarges and folds, forming two blind 
appendices, which are in turn divided into two parts each. 
The digestive tube continues to enlarge slightly until it reaches 
the region of the tenth segment where it narrows into the rectum 
which is not functional in later stages. The intestine contains 
a peritropic membrane for inclosing undigested food. Four 
tubes of Malpighi extend anteriorly from the region of the twelfth 
to the tenth segment. The anus is in the fourteenth segment. 
Here are also two symmetrical anal flaps which are easily visible 
when protruded. The larva contains well developed fat-bodies, 
