( 104 ) 



patch of Bubercct scales. I'eiiis-sheath with a very minute apical lobe indicating 

 the tooth of the allied Sphingidae. 



? . Antenna almost cylindrical. 



Il((li. Mexico ; Honduras ; probably more \vid(!ly distributed in ( 'entral America. 



XXVI. ISOGRAMMA gen. nov.— Typns : hageni. 



Cn-otomid, Grote («»« Harris, 1839), Bull. Buff. Soc. N<it. Sci ii. p. 149 (1874). 



D,in>,i,m„, id. {non Walker, 1856), /.«•. iii. p. 224 (1877). 



Sj,liin.e, Strecker («f(» Linne', 17.58), Lep. Rhop. Het. p. 127 (1878). 



S ?. Antenna of ? with a row of prolonged ciliae. Foretibia spinose at end ; 

 first segment of foretarsus little longer than second, with some long stout spines ; 

 niidti\)ia with a few spines at the very end, midtarsus without comb ; paronychium 

 and pulviHus present. Tubercle of labrum with sharp edge. 



$. Tenth tergite prismatically compressed, sulcata above, except at convex 

 apex, convex beneath, becoming carinate at end, apex curved downwards, pointed 

 in side-view, obtuse in frontal view ; sternite mesially divided into two conical 

 pointed processes (PI. XXVIII. f. 4) which are curved upwards at end. Ciasper 

 broadly sole-shaped, widest before middle, apex broadly rounded, a short, high, 

 subdorsal fold, ending where the ciasper widens dorsad ; harpe (PI. XL. f. 3) 

 scaled on surface as in Chlaenogrmnma, a pointed, fiugei'-like, ventro-distal 

 process, and a broad, short, rounded uj^per lobe, dorsal edge of harpe irregularly 

 dentate. Penis-sheath armed with an apical, conical, horizontal tooth which slants 

 distad a very little. 



?. Vaginal plate nearly as in Chlaenogramma, but the ridge before the month 

 of the vagina mesially deeper sinuate and somewhat impressed at the sinus 

 (PI. XX. f. 11). 



Larva covered with dispersed, transversely seriated granules, side-bands 

 bordered with red ; bead granulose (sub-triangular ?). 

 llab. Texas. 

 One species. 



In the shortness of the foretibia and first segment of the foretarsus the only 

 species of this genus agrees with the species of Ceratomia, and in the preservation 

 of the pulvillus with Chlaenogramma, while it differs from both genera in the 

 foretibia and the extreme apex of the midtibia being armed with spines. The 

 spinosity of the tibia is an advanced character, not acquired by Ceratomia, while 

 the pulvillus is an ancestral structure already lost in Ceratomia. Therefore the 

 genus Isogramma, though closely related to Ceratomia, is in one respect more 

 advanced than this, and in another it lags one step behind. This clearly shows 

 tliat Tsogramma and Ceratomia represent two divergent lines of development. 

 With a little power of construction it is not difficult to conceive that one and the 

 same link is missing both between Ceratomia and Chlaenogramma, and between this 

 and Tsogj-amma, this link being the common ancestor oi Isogramma and Ceratomia, 

 characterised by the possession of a pulvillus, not-sjjiny tibiae, and short and 

 strongly armed first segment of anterior tarsus. From this ancestral form hageni 

 branched off' by acquiring spinose tibiae (and in ? andromorphic antennae), 

 preserving the pulvillus, while Ceratomia became differentiated by losing the 

 pulvillus, but keeping the unarmed tibiae. A further diff"erentiatiou into three 





