628 SIDNEY I. KORNHAUSER 
Let us briefly review the possibilities of internal alteration 
which might affect the cells. The growing larvae depend en- 
tirely upon the host for their respiratory and nutritive needs. 
Oxygen must be extracted from the haemolymph or produced 
by the reduction of carbohydrates in the haemolymph. Carbon- 
dioxide must be poured back into the haemolymph by the para- 
sites. It is not unlikely that full-grown larvae distending the 
abdomen of the host interfere with its respiratory movements. 
Should an insufficient supply of oxygen be furnished the ¢ells 
of the host, a condition of acidosis would result in the tissues. 
This would bring about the accumulation of droplets of fat in 
the cells and lead to the degeneration of many cells. Micro- 
scopic examination shows much fatty infiltration and the accu- 
mulation of adipose tissue around the Aphelopus larvae. This 
tissue probably forms one of the chief sources of energy for the 
development of the parasites. But not only energy is needed, 
proteins must be supplied as well by the haemolymph of the 
host. In growing the parasites must give rise to nitrogenous 
waste materials. The premegagnathic larvae, which can alter 
an adult considerably if present before the final molt, probably 
excrete these waste materials directly into the haemolymph of 
the host. In the megagnathic larvae at least part of the kata- 
bolic products are deposited as insoluble crystals in the digestive 
tract. There is a possibility that nitrogenous excretions from 
the larvae might be toxic. Parasitic worms have long been 
known to give rise to toxic excretions (Firth, ’03). These toxins 
might act indirectly upon the developing cells. In Thelia, as in 
all homopterans probably, there exists a tissue well organized 
and of considerable size, arranged segmentally in the abdomen, 
and known as the pseudovittelus. This tissue, in which sym- 
biotic fungi develop, is thought to be very important in the metab- 
olism of the animal. In parasitized Thelia the pseudovittelus 
is much reduced, although I have seen no indications of fatty 
degeneration in its cells. This reduction of the pseudovittelus 
might also alter the composition of the haemolymph. With the 
possibility of so many alterations in the haemolymph which 
bathes the cells and furnished them with food and oxygen, a 
