AQUATIC MIDGES AND SOME RELATED INSECTS. 45 



Chironomus mandibles (fig. 51). These were used by the larvae for the purpose of 

 locomotion. They move alternately, and the head is tipped down slightly, so that their 

 motion in a dorso-ventral direction enables them to function as feet. In this species 

 the anterior prolegs are entirely lacking, and the larva moves by a gliding eel-like motion 

 aided by the mandibles, which also help to clear the way. A similar function of the 

 mandibles in Culicoides sp. is suggested (figs. 46 and 47). 



The labium has several times been figured showing a strongly chitinized central 

 tooth and in some species a single pair of lateral points on the otherwise smooth, some- 

 what thickened lower margin of the head. This central tooth appears to be the hypo- 

 pharynx. Its probable function as a piercing organ would doubtless be suggested to 

 everyone by its shape. 



The epipharynx in Culicoides sp. seems to be located near the middle of the head 

 and, so far as it is possible to tell from drawings, what the author considers as the epi- 

 pharynx (figs. 46 and 47, ep) is what has been called the hypopharynx by Malloch 

 (191 5). Its function seems to be that of a strainer or comb, coupled doubtless with a 

 tactile function. 



The ventral half of the head seems to be fitted with long muscles which doubtless 

 operate the mouth parts. The dorsal half of the head posterior to the epipharynx 

 seems to be filled with radiating muscles, as described in the case of the Tanypina, 

 which doubtless serve a similar function, namely, that of a pump or sucking organ. 



FEEDING HABITS. 



Culicoides (guttipcnnis?) larvae, which were under observation for some time, were 

 extremely hard to observe while feeding. The only case actually seen was that of a 

 larva feeding within the dead body of a pupa. This pupa was of the same species as 

 the larva. When observed, the body of the larva was thrust deep into the nearly empty 

 shell. The larva was revolving its head and first two segments about, and of course 

 could not bring pressure upon its mouth parts because of its lack of prolegs. It seems 

 probable that the mandibles came into use at this time, as they are the only mouth 

 parts adequate to the purpose. It was impossible to observe the activity of the mouth 

 parts on account of the thickness of the chitinous wall. 



The author's experience in trying to study the stomach contents of these species is 

 exactly parallel to that of Miall and Hammond (1900), who were unable to identify the 

 small particles occasionally found in the stomach. According to these same authors 

 ' 'The digestive system is straight and simple and apparently adapted to the wants of a 

 carnivorous animal." 



From the obvious specialization of these aquatic larvae, as shown by their relatively 

 great length and slight breadth, it seems fair to assume that they are adapted to an 

 environment where they are able to reach food inaccessible to thicker and more chubby 

 larvae. During the winter larvae of an aquatic species were found deep in various 

 decaying stems, especially those of Typha and Sparganium. The following summer 

 the writer was unable to find them in connection with these stems, but by dipping up 

 masses of floating green algae in the same pool he found them in considerable numbers. 



What then is the nature of the food upon which the larvae of the Ceratopogoninae 

 live? It seems probable that larvae living under decaying bark, in rotting onions, 

 among decaying elm leaves, or under cow dung would have but little choice in the food 



