632 Mr. L. G. Saunders on the Larva^ 



of the early stages^ accompanied by a discussion of tlie 

 other insect-larvae which liye under similar conditions. 



Bezzi (1913) is still of the opinion that Orphnephilq, repre- 

 sents a distinct family, related on one side to the Blepharo- 

 ceridse and on the other to the Psychodidge-Culicidse and the 

 Chironomidse, but not to be joined to them, being of earlier 

 origin than any of these groups. He based his opinion on 

 a critical study of the adults and his own interpretation of 

 the larva apparently from Thienemann's description, since he 

 furnishes no additional morphological characters. 



In 1914 Thienemann sent material of the immature stages 

 to Dr. D. Keilin at the Laboratoire d^E volution des Etres 

 Organises, Paris. Unfortunately, pressure of work prevented 

 Dr. Keilin from studying the characteristics of the larva^ 

 and he has now very generously permitted me the use of the 

 original material. 



Habits of Larva and Pupa. 



For the benefit of those who may wish to search for this 

 interesting species, the details of the life-history as far as 

 known are here reproduced from Theinemann^s paper. 



The eggs and oviposition are unknown. 



In habitat the larvae are very specialised, being found only 

 in small brooks and streams where clear clean water flows 

 very thinly (about 1 mm. deep) over rocks, so that the back 

 of the larva is always exposed above the surface. The food 

 of the larva consists of vegetable detritus and diatomes. 

 When searching for food a creeping motion is employed, 

 using the prothoracic pseudopod and mandibles after the 

 manner of Chironomids. Easter progression is achieved by 

 a special method which Theinemann states from his very 

 wide experience to be different from that of any other 

 dipterous larva ; the fore part of the body is bent sideways 

 in an inverted U drawing the posterior end of the body as 

 far forward as possible, and then straightened out again 

 suddenly, the venter always remaining in contact with the 

 substratum. A consecutive series of such motions performed 

 rapidly enables the larva to proceed at a good pace. 



Pupation and emergence occur from summer to late 

 autumn (November). The pupae lie on the bottom between 

 stones and aquatic plants, and are not seen as frequently as 

 the larvae. 



Description of Larva. 

 The following description of the colour and appearance of 



