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XVIII. Contribution towar&> the history of a new form 
of larvse of Psychodidse (Diptera), from Brazil. 
By Dr. Fritz Muller, M.D., Hon. F.E.S. 
[Read Oct. 2nd, 1895.] 
Plates X. and XI. 
The perusal of Baron Osten Sacken's Contributions to 
tlie Study of Liponeurida3 (Berl. Ent. Zeitsclir., 
vol. xl., 1895, p. 148), a copy of which I owe to the 
kindness of the author, recalled to my memory a group 
of minute Diptera, the larvae of which abound around 
the waterfalls in our woods, in the neighbourhood of 
the larvse of Gurupira {BlepharoceridsB) , and are re- 
markable for being provided, like the latter, with a 
longitudinal row of suctorial ventral discs. 
While the larvae of Ciirupira are fastened to the bare 
rocks, over which the stream of water falls down per- 
pendicularly, those of the Maruis {Marui is a diminutive 
of MarH, fly, in the Tttp^*- language, adopted in Portu- 
guese) live on rocky walls, covered with a slippery 
carpet of algae, and kept moist by the spray of the 
waterfalls or by the drops of water running down from 
above. I discovered them in 1881 in looking for a small 
Helicopsyche that occurs in similar localities, and began 
to make a special study of them, but was prevented by 
circumstances from continuing it. The information I 
had obtained about them seemed to me too fragmentary 
for immediate publication. As I cannot, at present, 
expect to complete these observations, although I had 
hoped it at that time, I feel inclined to publish now at 
least some of my old drawings, and to accompany them 
with some remarks for the sole purpose of calling the 
attention of future visitors to our country to these 
remarkable animals. 
For this particular purpose I shall begin by describing 
my very simple method of catching them. The larvae 
are so small that they are hardly recognisable in situ, 
TRANS. ENT. SOC. LOND. 1895. — PART IV. (dEC.) 
