40 CONNECTICUT GEOL. AND NAT. HIST. SURVEY [Bull. 



lapping mandibles, ind^ which intervene between the labruni, Zr, and 

 the hypopharynx, lif^ so that the hypopharynx (which is pierced by 

 the salivary canal) does not form the floor of the food channel — as it 

 frequently does in other Diptera. The overlapping: mandibles also 

 intervene between the labrum and the hypophar^aix, in the resting po- 

 sition, in the Ceratopogonidae {Ctilicoides) and Simuliidae, which, 

 however, are onW distantly related to the Tabanidae, The galeae, g^ 

 of Tabanus (Fig. 4, G) form a trough in which the hypopharynx, Ap, 

 lies, and all of these mouth parts, excepting the maxillary palpi, lie 

 in the labial gutter, or trough of the labium (which is not shown in 

 Fig. 4, G). When a female tabanid prepares to puncture the skin, the 

 jabellar lobes are drawn back so as to expose the maxillae and man- 

 dibles, which are forced into the wound when the insect bends its head, 

 and, by rapidly repeated movements, they extend the puncture into 

 the blood-containing tissues. The lobe-like labella (which cannot 

 puncture the skin) are provided with pseudotracheae into which the 

 blood enters, and passing into the collecting channels, is carried 

 through the "oral aperture" into the food channel, from which it is 

 sucked up into the fulcral pump, or first food pump. A second food 

 pump (called the ''oesophageal" pump by Peterson, 1916) takes up the 

 blood from the first pump, and passes it on into the so-called oesoph- 

 agus, etc. (Two somewhat similar food pumps likewise occur in mos- 

 quitoes. ) 



In the blood-sucking Muscoidea (sensu lato) , such as the stable fly, 

 tsetse flies, etc., the proboscis is made up of the same ])arts as those 

 found in the non-bloodsucking muscoids,* so that the diagram shown 

 in Fig. 4, F, would serve equally well to illustrate the general rela- 

 tions of the mouth parts in either type of fly. In the ^luscoidea the 

 mandibles are atrophied, and the maxillary galeae usually become 

 vestigial, while the distal parts of the labium become of increasing 

 importance for taking up the food. The labella, which are provided 

 with pseudotracheae, prestomal teeth, etc., in the typical muscoid flies, 

 jDlay a leading role in the feeding operations of these flies; and when 

 the labella are reduced (and hardened) so that they will not impede 

 the piercing operations of the labium in the blook-sucking flies, the 

 prestomal teeth and interdental armature, borne on the labella, are de- 

 veloped for cutting into the skin, and largely serve to draw the labium 

 into the wound. In the blood-sucking Muscoidea, as well as the non- 

 bloodsucking ones, the food channel is formed by the labrum and 

 hypopharynx (which is pierced by the salivary canal), the roof and 

 sides of the food canal being formed by the labrum, Ir of Fig. 4, F, 

 while the floor of the food canal is formed by the hypopharynx, hp. 

 The first food pump (or fulcral pump) is well developed in these flies, 

 in which the second food pump (called the "oesophageal" pump by 

 Peterson, 1916) is not developed. 



In the Nycteribiidae (Fig. 7, B), the slender portion of the pro- 

 boscis beyond the bulbous region of the haustellum is formed by the 

 elongated labella (according to the later interpretations of Jobling 



*It is quite probable tliat piercing- mouthi parts arose independently in certain types of 

 blood-sucking flies among the higher Diptera. 



