36 GEO. H. HORN, M. D. 



suddenly narrowed behind the posterior eyes. Head beneath very 

 convex, twice as wide' as long, form irregularly hexagonal, posteriorly 

 eniarginate at middle, median line with a moderately deep depression at 

 middle. Anterior margin trilobed and formed as in Tetracha. 



Eyes as in Tetracha although the lower eye of the smaller pair is 

 very indistinct and may escape observation. 



Antenna arising above and behind the base of the mandibles, 

 four jointed, first joint stout, second longer and equal to the next two 

 together, joints 3 — 4 more slender the terminal shorter. All the 

 joints have moderately long whitish hairs. 



Mandibles as in Tetracha. 



MAXiLLiE with the small triangular basal piece, second joint (cardi- 

 nal piece), moderately stout attaining the sides of the head and with 

 a few setEB in front, third piece with the inner lobe tridentate near the 

 tip and a moderately long more slender terminal articulation. Palpi 

 shorter than the inner lobe, three jointed, joints gradually longer but 

 more slender from first to third. 



JMentum oval in form, narrower at base, basal portion feebly 

 corneous, apical portion membranous. Palpi two jointed, first joint 

 stouter and longer than the second and with moderately long stiff 

 hairs. 



Prothorax more than twice as wide as long, crescentic. apical 

 margin deeply bisinuate, disc feebly convex, median line finely im- 

 pressed, a slight sinuous impression each side, posterior and lateral 

 margins with moderately long whitish hairs. 



Mesothorax less than half as wide as the prothorax, similar in 

 form to that of Tetracha. 



Metathorax as wide as mesothorax and a little shorter. 



Abdomen. — Segments 1 — 4 gradually longer; fifth segment longer 

 gibbous posteriorly and emarginate and on each side of emargination 

 a slender tubercle, hooks one on each side, long, slender, directed in- 

 wai-ds and forwards; segments 6 — 9 gradually narrower, anal segment 

 moderately long, truncate, anal opening terminal. 



Legs as in Tetracha. 



SriRACLES as in Tetracha. 



The specimen before me was collected by Mr. H. G. Hubbard, near 

 Detroit, and is now the property of the Museum of Comparative 

 Zoology at Cambridge. 



The essential difi'erences between the four larvae just described are 

 as follows : 



