370 



PSYCHE. 



[January 1S93. 



one. There is quite an important dif- 

 ference between Oecacta and the present 

 form in the shape of the eyes, which in 

 the latter are reniform or deeply hol- 

 lowed out on the inside margin, the an- 

 tennae being set in a cavity partially 

 enclosed by the excavated orbit. In 

 this respect it resembles Simulium and 

 most of the Cecidomyiidae and Chiro- 

 nomidae. Judging from the plate (see 

 plate 27 of Poey's Memoirs on the Nat. 

 Hist, of Cuba, vol. I). Oecacta does 

 not possess this peculiarity. Cerato- 

 pogon has the palpi 4-jointed, and the 

 conformation of the antennae is peculiar, 

 especially in the $ . It must be remem- 

 bered that I have only 9 specimens of 

 the present species, and that the anten- 

 nae of the $ may or may not be differ- 

 entiated in form. 



The present form, with the genera 

 Ceratopogon (including Heteromyia 

 vSay) and Oecacta, possibly also Dia- 

 mesa, differ to quite an extent from the 

 rest of the Chironomidae. As a group, 

 they nearly approach the Anaretina in 

 their venation, the present genus 

 showing the greatest resemblance in 

 this respect, and differ from the other 

 Chironomidae by the body and wings 

 being shorter and stouter, not culicid- 

 like or elongate and narrowed, as in 

 Chironomus, Tanypus, et al. The ven- 

 ation is simpler; and the lancets and 

 labium are more elongate, and about 

 equal in length. 



The form here figured differs so ob- 

 viously from those genera already de- 

 scribed that there seems no question of 

 the advisability of making it the type of 



a new genus, which I shall call Ter- 

 sesthes (Gr. Tepo-eo-Oai, to become dry 

 or thirsty) . Its characters are as fol- 

 lows : 



Tersesthes nov. gen. § (see plate 8). 



Antennae 13-jointed, set in large circular 

 excavations in the middle of the head; first 

 joint largest, round; second joint more 

 elongate, smaller, but larger than following 

 joints; last joint elongate conical; interme- 

 diate ten joints equal, sub-moniliform, with 

 hairs somewhat shorter than width of joints. 

 Palpi 3-jointed, longer than proboscis, first 

 joint shortest, second joint swollen, third 

 narrow with a terminal whorl of hairs; 

 proboscis consisting of a lower lip (labium), 

 with the lancets free but usually more or 

 less approximated to its anterior aspect, both 

 of equal length, extended straight downward, 

 about as long as the head, lancets serrate on 

 outer edge at tip. No ocelli. Eyes reniform, 

 rather deeply excavated on inside margin, 

 dichoptic, front averaging one-third width of 

 head. Thorax moderately stout, but not 

 humped, a little wider than head, longer 

 than wide, without transverse suture, scutel- 

 lum prominent. Abdomen 7-jointed, some- 

 what elongate, not wider than thorax, first 

 three segments subequal, fourth smaller, 

 three terminal segments narrowed; ovi- 

 positor exserted, consisting of two clavate 

 pieces joined laterally on basal half and 

 terminally divergent. Wings moderately 

 broad, not elongate, hind margin with a 

 delicate fringe of hairs, surface sparsely 

 clothed with very short microscopic hairs 

 (revealed only with a high objective) ; six 

 longitudinal veins, the first and second 

 approximated, strongest, ending at about 

 one-third the length of wing ; third gently 

 curved distally and ending near the wing 

 apex, fourth apparently forked, fifth 

 distinctly forked, sixth becoming obsolete 

 before fork of fifth; an apparent rudiment of 

 a seventh vein; no cross-veins, except one 



