70 



cluster of hooks. The labium corresponding to the second pair of maxillae 

 is a single plate transversely elongated, lying beneath and behind the 

 mouth, its fore edges are armed with a row of small denticles. On the 

 under side of the prothorax is a pair of appendages, so completely united 

 as to resemble a single limb (which in chironomus are paii-ed). The free 

 extremity is furnished with a suctorial disc, whose edges are armed with 

 a multitude of fine hooks, arranged in radiating rows. This organ can be 

 retracted by means of a pair of long muscles which pass to the side of the 

 thorax. None of the remaining segments carry appendages until we come 

 to the last abdominal segment. Here, again, we find the paired 

 appendages, seen in chironomus, which are replaced by what looks at first 

 sight like an additional segment. It forms a suctorial cup, like one of the 

 suckers on the arm's of a cuttle fish. The raised margin is provided with 

 rows of tine teeth, very like those of the prothoracic limb. Within the 

 contracted cup, formed by the united anal feet, are three papillae, which 

 are alterable in shape, and may be protruded or withdrawn into the 

 rectum at pleasure. These papillae are, perhaps, used for loosing the anal 

 foot. The anus is situated in the construction just in front of the 

 contractive disc and on the dorsal side of the body. Alimentary Canal.— 

 The oesophagus is a simple tube furnished with transverse muscles, and is 

 deeply folded into the proventriculus or crop. The stomach is long, 

 cylindrical, and simple. Both crop and stomach are lined by a chitinous 

 membrane, which encloses the food, as in chironomus, crane fly, blow fly, 

 and various diptera. Two small malpighiau tubules are given oft' on each 

 side at the commencement of the intestine. The salivary glands are 

 simple, but extremel}- long. They extend to the hinder end of the body, 

 and are then bent forward to about one-third of its length. The salivary 

 ducts open upon a prominence or thread organ on the floor of the mouth 

 a little in front of the labrum. The use of this thread is for mooring the 

 larva, and for making pupa case or cocoon. The body of pupa projects 

 about one-third of its length out of the opening of the cocoon, and is 

 provided with respiratory tufts of four pairs on each side, situated on the 

 fore part of the dorsal side of the thorax. In the development of the head 

 of the fly many of the organs appear in the larva, as in chironomus, culex, 

 and corethse. The compound eyes, for example, can be easily seen near 

 the simpler eyes of the larva. There is an important difference in the 

 development of simulium as compared with chironomus. In the latter 

 nearly all the organs of the head are developed in the prothorax, whereas 

 in simulium the new parts form beneath the corresponding organs of the 

 larva. The imago is a small two-winged fly, with large and enormously 

 arched thorax. In hot countries some of the simulidse, and especially on 

 the banks of great rivers, are a great annoyance to men aiijd cattle. Tiie 

 bite raises a small blister. In Hungary and the Lower Danube they are 

 sometimes very mischievous ; the cattle become furious, and rush wildly 

 about, rubbing their hides against trees and rocks. The fly attacks the 

 corner of the eye of man ; the species is S. maculatum, or a closely allied 



