N0.1371. NEW DRAGON-FLY NYMPHS— NEEDII AM. 7u7 



Since the above Avas written I have .seen another specimen in the 

 Museum of Comparative Zoology, from Cache Valley, Utah (No. <;.■,;•). 

 collected ])y C. Thomas. 



SYMPETRUM MADIDUM Hagen ? 



A single fully grown specimen was collected for the United States 

 Fish Conmiission by Mr. Chauncey Juday in Lake Creek at Twin 

 Lakes, Colorado, on August 12, 1902. It is more strongly chitinized 

 than usual for nymphs of the genus, and differs from all others known 

 to me in the extreme reduction of the dorsal hook on the eighth 

 abdominal segment and in the relatively greater length of the lateral 

 abdominal appendages. Its reference to madldvia is more or less 

 doal)tful. S. decisinii and S. ati'ij}^;^ both belong to the Colorado 

 fauna. 



Length (fully grown), Itt.o mm. ; abdomen, 9 nmi. : hind femur. 4.5 

 mm.: width of head, 4.5 mni. ; of abdomen, 5 mm. 



Body short and rather stout, smooth. Head widest across the 

 anterior portion, where the e^^es are rather prominent and are set well 

 forward. The top of the head is smooth and the obtuse hind angles 

 are strongly hairy, while the hind margin is nearly straight — perhaps 

 slighth' concave. Antennae slender and hardly longer than the head, 

 the length of the segments from the head outward being in the fol- 

 lowing ratio: 1:2:3:2:2.5:3:2.5. Labium of the proportions usual 

 for the genus, with about 12 mental setse each side, the lifth or 

 sixth (counting from the side) longest. Lateral setae 12, diminishing 

 in size toward the base, the hook setiform, about as long as the seta 

 behind it. Teeth subobsolete, with the usual groups of spinules. 



Legs slender, smooth. Wing cases reach the middle of the sixth 

 abdominal segment. Abdomen moderateh' depressed, and with rather 

 sharp lateral margins. Lateral spines on segments 8 and 9. straight, 

 on 9 al)Out as long as the segment and twice as long as on 8. Dorsal 

 hooks represented on segments 5-8, well developed on and 7. smaller 

 and erect on 5, and on 8 rudimentar}' and very inconspicuous. Seg- 

 ment 8 of abdomen slightly and segment 9 strongly concave on hind 

 dorsal maTgin; 10, annular, included in the apex of 9. Appendages 

 very unequal, the superior a])out three-fourths as long as the inferiors, 

 its tip attaining the level of the tips of the lateral spines of the ninth 

 segment. Laterals three-fourths as long as the superior. Superior 

 and inferiors with spinous margins, stout triangular pyramidal bases 

 and acuminate points set at an angle with the l)ases and directetl pos- 

 teriorly, while the bases are directed upward. Laterals pale yellowish. 



