44 BULLETIN OF THE BUREAU OF FISHERIES. 



form was not bred, but from the mouth parts it seems possible that this is a myceto- 

 philid and not a chironomid at all. 



The typically terrestrial forms have well-developed anterior and posterior prolegs. 

 Perris's (1847) observations on Ceratopogon brunnipes and C. lucorum, together with 

 a study of the aquatic species already mentioned, would indicate a series of intermediate 

 stages between those with both anterior and posterior prolegs and those without either. 

 The author has indicated one stage of this series above. The first stage has caudal 

 filaments which replace the posterior prolegs. The other stages are represented by 

 the two species described by Perris. The first, Ceratopogon brunnipes, he found in 

 decaying mushrooms at the foot of a poplar tree. Of this species he says the anterior 

 prolegs are deeply dilobed and each lobe is furnished with a few claws. These are 

 completely retractile, but those of the posterior prolegs are not. The other species, 

 Ceratopogon lucorum, he says, appears to have a proleg formed of two pieces united by a 

 suture, each of which is feebly bilobed. The exterior lobe is bare, and the inner lobe 

 is furnished with fine spines. The last species, found in decaying elm leaves, resembles 

 the typically terrestrial forms in general ; besides possessing both anterior and posterior 

 prolegs it has a spiny body. 



In considering the terrestrial nature of these larvae Laboulbene (1869) says that 

 stigmates certainly exist but that he has not been able to count the openings. His 

 opinion that they really do exist seems to be due to his observations on the arrange- 

 ment of the tracheae. The authors quoted in regard to the variety of habitats occupied 

 by the larvae of the Ceratopogoninae all emphasize the humid condition of the habitat, 

 and in the absence of any direct observations on the presence of spiracles it seems 

 probable that in this respect at least the group is a unit. 



HEAD STRUCTURES. 



To understand the feeding habits of any insect, the structure of the mouth parts 

 lends an important clue. This is equally true of the mouth parts of the larvae of the 

 Ceratopogoninae. The frequency with which the early students complain of the diffi- 

 culties of such a study is a sufficient justification for a somewhat incomplete 

 consideration of these structures here. 



In the aquatic larvae Culicoides sp. ?, probably C. guttipennis, the head is long and 

 slim, about four times as long as wide. The antennae, so conspicuous and useful in the 

 other subfamilies, are here very slightly developed, scarcely reaching to the anterior 

 border of the head. Their location (fig. 45) on the dorso-lateral border of the head, 

 together with their slight development, fits them to serve as a sense organ with only a 

 very limited function. This slight development of the antennae is characteristic of the 

 entire subfamily and is doubtless associated with the nature of the food consumed. 



The mandibles, in Culicoides sp. ?, possibly guttipennis, are quite characteristic 

 structures (figs. 46, 47, md). They are so hinged as to be capable of being extended 

 beyond the head and are opposable. They are also often observed within the head 

 with their tips pointing backward, showing that they have a wide range in their move- 

 ments. The fact that the mandibles are capable of being swung through such a wide 

 angle shows that they are doubtless very essential to the feeding habits of the larvae. 



The larvae resembling Laboulbene's larvae which the author found in the sap flows 

 on elm trees about Ithaca have mandibles with teeth resembling those on the typical 



