46 INTERNAL ANATOMY OF INSECTS. 



spiracle over each of the four last legs of the Libellulina a , 

 but in the remainder of the Neuroptera Order they have 

 eluded my search. In the Hyrtienoptcra and Diptera 

 they are nearly in the same situation, being placed be- 

 hind the wings on each side of the metathorax ; in the 

 latter Order with the poiser near them on the inner side b : 

 in this also, the spiracles of the trunk are without lips, 

 except in the larvae, but are often merely an orifice, 

 sometimes fringed with hairs ; this is particularly con- 

 spicuous in Syrphus, in which these orifices are very 

 large, and in some species closed by an elegant double 

 fringe of white hairs. This is doubtless to prevent the 

 entrance of any particles of dust or the like. 



We are next to consider the situation of the spiracles 

 of the abdomen : these which are supposed to be appro- 

 priated exclusively to inspiration, are usually more nu- 

 merous than those of the trunk, by which it is probable 

 that expiration is performed, and have principally at- 

 tracted the notice of Entomologists : they are either dor- 

 sal, lateral, or ventral. In Dytiscus, Copris, &c. amongst 

 the beetles, all the spiracles are dorsal; in the larvae of 

 Coleoptera and Lepidoptera they are lateral ; and in the 

 Heteropterous Hemiptera they are usually ventral: in 

 Dynastes they are commonly found of all three descrip- 

 tions; the three first being dorsal^ the two next lateral, 

 and the last pair ventral c . In some instances, as in 

 Perga Kirbii, and probably other Hymenoptera, these 

 organs are planted in that portion of the dorsal segment 

 which turns under, as was observed in a former letter d , 



a Chabrier sur le Vol des Ins. c. iii. t. vi./. 4. Sa, Sp. 



i' PLATE IX. FIG. 21. m". 



* PLATE VIII. FIG. 9. * VOL. III. p. 705-. 



