ANATOMY OF MARELLIA REMIPES — CARBONELL 



83 



contribute to siibaqnatic breathing. We must recall here that the 

 mesothoracic spiracle (fig. 8, Sp-z), covered by the posterior part of 

 the lateral lobe of the pronotum, is also unusually large, and also has 

 a hairy zone in its neighborhood. These characteristics lead us to 

 think that the mechanism for subaquatic breathing comprises three 

 pairs of spiracles — the mesothoracic and the first two abdominal ones 

 —the three of them protected by adjoining structures and connected 



PN3 IT IIT 



Cer 

 YIIITiEppt/pt 



-:r^Ovp 



VllSp VIIS 



Cxs IS IIS 



Fig. 15.— Abdomen and base of thorax of Marcllia remipes, female. 

 Cer, cercus ; Cxz, coxa! cavity of hind leg ; Epm, epimeron ; Eppt, epiproct ; 

 Eps, episternum; Ovp, ovipositor; PA''.-!, metathoracic postnotum ; Ppt, paraproct; 

 Sz, metathoracic sternum ; IS, IIS, VIIS, first, second, and seventh abdominal 

 sterna; VIIIS, eighth abdominal sternum, or genital plate of the female; ISp, 

 lisp, VIISp, first, second, and seventh abdominal spiracles; IT, IIT, VIIIT, 

 first, second, and eighth abdominal terga ; Tm, tympanum. 



with zones of hydrofugous hairs retaining air bubbles. Unfortunately 

 the writer has not had on hand live specimens to prove these infer- 

 ences at the time of making this study. 



The rest of the abdominal spiracles (see fig. 15) are located rather 

 high on the lateral parts of the tergal plates. An unusual detail of the 

 female abdomen is the absence of spiracles on the eighth tergum, the 

 last pair being on the seventh (VIISp). The male abdomen, on the 

 contrary, has a pair of spiracles on the eighth tergum (see fig. 19 A, 

 VIIIT). The lack of spiracles on the eighth tergum of the female 

 abdomen is a curious fact for which the writer has not been able to 

 find an explanation, unless it is related in some way to oviposition 

 under water, to which we shall refer later in this paper. 



The cerci (figs. 15, 16 B, 19 A, B, Cer) are similarly shaped in 

 both sexes. They present a bulbous basal part which tapers to a 

 bluntly pointed apex. In the male they are longer and slightly curved 

 inward. 



