BOLLETTINO 



DM 



Musei di Zoologia ed Anatomia comparata 



. „ dfilln IL Università di l'orino 



n.qr ^ 



N. SS± pubblicato il 29 Maggio 1899 Vol. XIV 



Viaggio del Dr. A. Borelli nella Repubblica Argentina e nel Paraguay. 



XXIV. 



G. W. KlRKALDY 



AQUATIC RHYNCHOTA 



1. Gerris spp. ? - Nymphs in various stages. 

 Argentine — Resistencia (Chaco); S. Pablo, Tucuman 



2. Gerris Sp.? - S. Pablo, Tucuman; Tala. 



A species allied to, but probably distinct from G. Perseus and An- 

 dromeda. Only nymphs in the ultimate stage are in the collection, with 

 the elytra largely developed, extending to one -half ofthe total length 

 of the abdomen and very pilose. Also a single much younger nymph 

 probably of the saune species, from S. Pablo. 



3. Gerris Perseus sp. n. 

 Belonging to typical subgenus. 



Head elongate, narrow,- pronotum deeply sulcate between anterior 

 and posterior lobes, the latter reaching to only about i / 4 th of the total 

 median length ot the mesonotum. Rostrum reaching beyond apex of me- 

 sosternum. Mesosternum longitudinally widely sulcate; metasternum and 

 abdomen not cannate, metasternum obsoletely tuberculate. Posterior 

 intermediate tibiae tarsi curved. 



Average proportions: Head 29. Pronotum 32 (24 -+- 8), mesonotum 34 

 (median line), metanotum 14. Abdomen 63 (46 -f- 17). Antennae 30: 18: 

 19 : 18. Anterior legs [see below]. Intermed. femur 120, tibia 114, tarsus 

 76 (63-f-13). Posterior femur 120, tibia 74, tarsus 37 (25 + 12). 



The anterior legs are most extraordinarily variable in proportionate 

 length, more so than in any other aquatic Rhynchoton I have critically 

 examined. Of the present species I have examined 9 examples, ali males; 

 the proportions of the anterior tibiae and tarsi being : 





