246 ANATOMY. 



remain in immediate connection with the base of the wings, from 

 this being contracted and narrowed, whereby the scale is separated 

 from the wing. We nevertheless still find in many Dipt era a con- 

 nection. It is remarkable, and confirmatory of this opinion, that those 

 Diptera which want this scale, are such whose wings stand off in a 

 state of repose, as, for example, in Tipula. But this frenum passes 

 always from the superior wing to the lateral margin of the scutellum, 

 and the scale of the Diptera is always found in this situation. The 

 Lepidoptera are not deficient in this membrane ; in the Hemiptera 

 (for example, Cicada, Plate XIII. No. 5. 1.), it is partially horny; 

 in the Hymenoptera it has but small compass, but in these it is not 

 either ever wanting. 



The connexion of the posterior wings is still more intimate than 

 that of the anterior pair, whenever they are larger than the latter. 

 The Coleoptera exhibit towards the base of the wing several plates, 

 which lie free in the membrane, and which, like those of the elytra, pro- 

 mote and support their motion. Straus distinguishes five in Melolontha, 

 and calls them axillary pieces (\.prcaxillaire, and 4. axillaires"). 

 Neither is the connecting membrane which runs from the last portion 

 of the joint to the margin of the metathorax wanting here. This is 

 likewise the case in the large posterior wings of the Orlhoptera as 

 well as of the Dictyotoptera and Nturoplera, in which the plates and 

 membrane are also found, and in the latter frequently very much de- 

 veloped. Nor is it wanting in the other orders. 



The Diptera are remarkable from having no posterior wings, but 

 instead of them they are provided with two pediculated knobs, which 

 are called halteres. Latreille and other French naturalists will not 

 allow these organs to be considered as the rudiments of the posterior 

 wings, whereas the majority of the earlier entomologists, and many 

 modern ones, particularly the Germans, consider them as such. If we 

 look to the situation of these organs, it speaks incontestibly in favour 

 of this opinion, for they are exactly situated where the posterior wings 

 of other insects are found. Besides, they stand in the same connection 

 with the metathorax ; and, indeed, in the larger flies, for example, 

 Tabanus bovinus, we detect the analogue of the connecting membrane. 

 The knob is also sometimes (Tipula gigantea, lutescens) broad, flat, 

 and provided with ribs like the wings, these are all facts which cannot 

 be disputed, and which corroborate the correctness of this opinion. 

 Latreille's decision, therefore, that the last segment of the thorax in 



