CALLIPHORA ERYTHROCEPHALA, MG. 285 



On the ventral side of the proboscis in the Crane-flies is a 

 second rod, with a shorter bifurcation, which seems hinged on to 

 several chitinous processes at the base of the labella. This 

 part, like the parallel rod above, when examined with higher 

 powers, is seen to consist of a fusion of two rods or plates, so 

 that it cannot be a modification of the mentuni, a homogeneous 

 plate, which we have seen is situated in a similar position in the 

 Blow- fly (Fig. 5). This ventral rod can also be found in species 

 of Bibio, Dilophus, and Pxychodidae-, all belonging to the older 

 group in the flies (Fig. 6). Two types of proboscis have been 

 examined, one the Blow-fly with plates above and below, and 

 levers at the posterior part, and the other the Crane-flies with 

 rods above and below, and without the levers at the posterior 

 end. 



We now take a third type, which resembles the proboscis of 

 the Blow -fly in the shape of the labium, and also has a number 

 of tracheae permeating the structure of the labella. This is the 

 proboscis of the Breeze-fly, Tabanus bovinas, L. If this be 

 examined it will be found that both the upper and lower surfaces 

 of the labium are without the plates and rods that are present 

 in the corresponding parts in the Blow-fly or the Crane-flies. 

 The reason is apparent when we find this insect furnished with 

 broad-bladed mandibles and strong maxillae ; to these maxillae 

 are attached the palpi, and their bases are fused to rods, which 

 represent the stipes and cardines, present in similar situations in 

 the Blow-fly, but absent from the base of the labium in the 

 Crane-flies owing to a migration to a more anterior position 

 (Fig. 13). 



We can now go a step further and examine the mouths of 

 some insects related to the Crane-flies which have, like those 

 insects, lost the armature that is present in Tabanus. Chiro- 

 noinns dorsalis, Mg., is without parallel rods in the median 

 line, although the levers of the maxillae are there, but in the 

 normal posterior position, separate and attached to the palpi, 



