24 BULLETIN OF THE BUREAU OF FISHERIES. 



12, p. 30) apparently contains a leaf-eating species, as Mr. Johnson states that Crica- 

 iopus sylvestris was bred by Prof. Smith from the leaves of Victoria regia. These two 

 species, so far as the author knows, are the only ones that feed directly on living plant 

 tissue. Other larvse, however, are found in the large air spaces of dead and living 

 aquatic plants, where they maintain themselves in the same way as while living in a 

 burrow made of trash. 



Dr. Pettit's note gives only a brief explanation of the nature of the damage done 

 and a general description of the larva and pupa based on the color characters. He bred 

 the adults and states that they belong to the genus Chironomus and are probably a new 

 species. Since the above quoted studies are substantially in agreement with the writer's 

 observations it would seem probable that all the above chironomid records refer to this 

 species. The unusual food habits and other unique adaptations seem to justify a rather 

 more comprehensive study of this species. 



GENERAL HABITS. 



The larva? of Chironomus brasenia; from a superficial examination would appear 

 to be true leaf miners. The straight or winding galleries are covered with a green 

 ridge, which closely resembles the epidermis in color, and the lower epidermis is left 

 intact. Closer examination, however, shows that the cover of the larval burrow is not 

 the upper epidermis but rather an artificial cover made up of plant fragments fastened 

 together with silk and moistened with a film of water which floods the entire burrow 

 and spreads out in a thin film a little way on each side of the burrow. The larvae can 

 also be seen when at work to actually project their body out onto the surface of the 

 leaf at times. They are completely immersed in the water which constantly floods 

 their burrows, and they breathe by blood gills. Their burrows are lined with silk, which 

 is also used in constructing the coverings of the burrows. The larvae of the typical rep- 

 resentatives of this genus do not carry their cases about with them as was erroneously 

 stated in his discussion of this species by Dr. Pettit. On the contrary, this larva 

 resembles the other members of the genus except in the method of obtaining and the 

 nature of its food. 



LIFE HISTORY. 



The life history differs in several important particulars from that of the typical 

 species of the genus Chironomus. The eggs are laid on the surface of partially submerged . 

 leaves of both the water shield and the sweet-scented pond lily (fig. 19). They are 

 laid in strings which tend to show a double arrangement of the eggs, due doubtless to 

 an egg coming from each ovary simultaneously. These egg strings are wound about 

 and crisscrossed in such a way that they form a somewhat disklike mass which tends 

 to be only one layer deep, the gelatinous coating fusing to unite the whole into a single 

 mass. In the limited area where the eggs were found most abundantly the leaves of 

 Castalia were selected rather more frequently than those of Brasenia, although the latter 

 is clearly preferred by the larva;. It seems probable that the chief factor governing the 

 selection of these leaves is their partial submergence, as the eggs are laid on the top 

 surface of the leaf and are unable to endure desiccation. 



The young larvae obtained from these eggs were placed on sections of Brasenia leaves 

 and confined there in drops of water. These preparations were placed in watch glasses 



