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MONOGRAPH OF THE LABOULBENIACE.E. 



hosts inhabiting the margins of running water were much more likely to be parasi- 

 tized than those found along the borders of ponds or of still water generally ; but this 

 has certainly not been my own experience, and the margins of ponds or of boggy 

 places generally have always proved as rich in Laboulbeniaceoe as those of brooks or 

 rivers. It is also worthy of note that the statement made by the same author that 

 iridescent hosts are not infected has not proved to be true in my experience. 



The relation of the parasite to its host as regards its nutrition has already been 

 referred to, and there can be no doubt that the fluids of the insect are absorbed by 

 osmosis through the membrane of the foot or haustorium, whether this be a highly 

 developed penetrating organ, as in Rhizomyces or Moschomyces, or consists merely in 

 a sucker-like external attachment. 



The relation of the parasite to its host, in position, is a matter of interest for sev- 

 eral reasons ; for, although all parts of the latter may be infested, the antennas, the 

 eyes, the mouth parts, the anal plates, — in fact any portion exposed when the insect is 

 at rest, — certain species exhibit a very remarkable definiteness in regard to their point 

 of attachment. In some forms, like Laboulbenia Nebrice, or L. Guleritce, the parasite 

 occurs indiscriminately all over the host ; others, like L. terminalis, L. fumosa, or L. lux- 

 uriaus, only at the tips of the elytra and the adjacent region about the extremity of 

 the abdomen. Others, like L. parvula and L. arcuata, have been found only on the 

 legs, the latter species always in a definite position. L. Harpali, again, occurs on one 

 side only, along the anterior inferior margin of the thorax and the adjacent margin of 

 the prothorax. L. contorta, L. umbonata, L. elegans, L. lepida and L. texana all occur, with 

 very rare exceptions, on the prothorax just below the external margin, usually on a 

 definite side; and it may be noted in passing that, especially as regards the ex- 

 tremity of the perithecium, all the last-mentioned species have a family resemblance. 

 Instances like those just enumerated might be multiplied ; but by far the most remark- 

 able examples occur in the genus Chitonomyces. Species of this genus growing, for 

 example, on Laccophilus maculosas, can be distinguished, as a rule, with certainty merely 

 by noting their relative positions. C. parodoxus is invariably fixed to the margin of 

 the left elytron about half-way between its base and apex ; C. marginatus occurs just 

 within the margin of the same elytron nearer the apex. C. lichanopliorus is found 

 only on one of the inferior median anal plates (always the same plate), and so on 

 through the list of twelve species that infest this host; the only instance which I have 

 noticed of any deviation in their position being in the case of C. margincdus, which is 

 rarely found attached to the left posterior leg. 



Why such constancy in position should exist in some cases, and not in others, is a 



