470 MAUD D. HAVILAND 
CoMPARISON OF THE LARVAL CHARACTERS or Charips 
WITH THOSE OF PARASITIC HYMENOPTERA IN GENERAL. 
The early larvae of the hypermetamorphic Hymenoptera 
Parasitica may be referred to three main groups : 
The first, or cyclopoid, type so far as has been found only 
in Platygaster (Proctotrypoidea), and is known chiefly 
through the researches of Ganin (5) and Marchal (20). 
In the second type the last segment is furnished with an 
appendage, and thus may be called caudate. It includes, 
for example, such forms as Limnerium (Ichneumonidae) 
Aphidius (Braconidae), Comys, and certain Agenias- 
pids (Chalcidae) and Teleas (Scelionidae). 
The third type was first observed by Wheeler (27) in the 
myrmecophagous Chaleid, Orasema, and has since been 
described by Smith (24) in another Chaleid, Perilampus. 
This larva, known as a planidium, is elongated and testudinate, 
furnished with imbricated plates of chitin. 
The caudate type is the most frequent. The function of the 
tail has been supposed by different authors to be either loco- 
motory or respiratory, but may possibly be both. In the 
early stages of such forms the tracheal system is apneustic 
and respiration is cutaneous. ‘The cauda, by increasing the 
body-surface, may assist in the absorption of oxygen, and the 
thoracic processes of Encoila may have a similar function. 
At the same time the setae with which the cauda is furnished 
in some Aphididae suggest that it may sometimes serve for 
locomotion. 
The first-stage larva of Charips is caudate, but I can 
find no other instance of heavy chitinization in this type. 
Indeed, the only parallel instance appears to be the planidium 
of Perilampus, whose life-history 1s somewhat different. 
Perilampus is hatched as a free living form, and later seeks 
out the caterpillar which contains the proper hymenopterous or 
dipterous host. It then lives as an endoparasite without growth 
or ecdysis fora variable time. After metamorphosis of the host, 
it emerges, sheds its chitinized skin, and completes development 
