102 
The Respiratory System of Mallophaga 
in the Gyropidae, the Trichodectidae, and Tetrophthalmus. The 
abdominal stigmata are dorsal, and mostly in segments 2-7. 
The value of this, the most recent statement of the tracheal condition 
in.Mallophaga, may be gauged from the facts that I set out in detail 
below, namely that the two main trunks are only exceptionally united 
by a posterior transverse commissure; that prothoracic stigmata are 
universally present; and that the abdominal stigmata are in almost 
the whole of one sub-order found upon segments 3-8, that in at least 
one case they are all ventral, and that in two genera there are but 
five pairs in place of the usual six. 
Possibly the difficulty of satisfactorily demonstrating the tracheal 
system has been the reason for the somewhat cursory treatment it has 
received. By the employment of suitable methods, however, I find that 
it is possible to trace the tracheal supply in great detail. As a superficial 
examination disclosed certain fundamental differences in the number 
and arrangement of the stigmata, and in the disposition of the tracheal 
trunks, I have thought it worth while to investigate the whole respiratory 
system as fully as the material available to me has allowed. 
Method of Examination. 
Living material is essential if the best results are to be obtained. 
In some forms, where the main trunks are of fairly considerable size, 
and the taenidia of sufficient strength to resist collapse on treatment 
with reagents, specimens cleared in potash and mounted into balsam 
show the more important trunks and branches. Heterodoxus, Tetro- 
phthalmus, and Docophoroides give good results with this treatment. 
I have seen some preparations of Mr B. F. Cummings in which acid 
fuchsin has been employed after potash with fair success. But for 
most genera, and for detail in any of them, live material is desirable. 
If the living insect be killed and dehydrated by immersion in absolute 
alcohol for about ten minutes, and then cleared and mounted, the 
tracheal tubes remain filled with air, and are very easily followed. 
Such a preparation is, however, not permanent, as balsam gradually 
replaces the air; but it will usually keep in good condition for several 
days. A still better method is to put the living insect direct into dilute 
glycerine under a coverslip, as the glycerine infiltrates the tracheae at 
a much slower rate, and has sufficient clearing action to render the 
smaller branches easily visible. Such a preparation will remain in 
good condition for several weeks. With pale forms, and with newly 
