THE INTERNAL ORGANS OF RESPIRATION. 179 



consequently be found in all flies whose larvae breathed through the tail 

 itself, or through spiracles seated there. The presence of this air 

 bladder explains the cause of the glassy perfectly transparent abdomen 

 of so many Diptera, for example, of Volucella pellucens, Meig. The 

 Asili, which have a longer, narrower, more extended abdomen, possess, 

 according to Marcel de Serres *, several small and successive vesicles, 

 for example, Asilus barbarus has sixty on each side. 



Many Hymenoptera display a similar structure. In some species of 

 Bombus I have found precisely the same air bladders at the commence- 

 ment of the abdomen, as has also Leon Dufour in Scolia f. 



Carus | has described them in the large Cicada. The air bladder 

 originates within the circumference of the large spiracle which lies 

 between the thorax and abdomen, it distends a little anteriorly, but 

 spreads especially backwards, where it extends to the sixth or seventh 

 segment ; before impregnation, whilst the ovaria and testes are still 

 filled with their contents, they are limited to a smaller space, but after 

 copulation they occupy almost the whole abdomen, particularly in the 

 males, in which they are generally larger in compass, doubtlessly in 

 connection with the vocal organ, which in the females is merely indi- 

 cated. Hence is explained the opinion of the ancients, who held that 

 the males were empty. 



In the grasshoppers the bladders have a somewhat different connec- 

 tion with the rest of the respiratory system ; and they also vary con- 

 siderably in form from the former, for in these they consist of bags of 

 a somewhat longish oval shape, very pointed at both ends. In Locusla 

 viridissima two such bags originate at each spiracle, they thence ascend 

 close to the inner side of the general integument up to the back, 

 where they attach themselves to a flat horny arch, which originates 

 from each ventral plate projecting into the cavity of the abdomen, and 

 which is affixed to the ventral plate only at its commencement. Each 

 of these arches supports two air bladders, which, however, do not pro- 

 ceed from one but from two separate spiracles, so that they altogether 

 form a zigzag line. But they are connected also above and below by a 

 narrow longitudinal tube, and from the lower ones there are vessels 

 connecting them with the opposite ones of the other side, and from the 

 upper ones originate the branches which are distributed to the internal 



. de Mus., as above, p. 362. f Journal de Physique, Sept. 1830. 



J Analekten zur Naturwissenschaft und Heilkunde. Dresden, 1828. page 158. fig. 

 1517,9. 



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