1970] 
JVhite and Raff — Williamsonia 
255 
period was over by that time. On 3 May the surface water tempera- 
ture was 15 0 ; 60 cm below the surface the temperature was 10°. 
In association with lintneri were nymphs of Libellula quadrima - 
culata L Sympetriun rubicundulum (Say), and Chromagrion 
conditum (Hagen). In addition an exuvia of Leucorrhinia hudsonica 
(Selys) was found in the same area. Later in the year this portion 
of the bog is inhabited by the above species as well as Gomphaeschna 
furcillata (Say), Nannothemis bella (Uhler), Leucorrhinia proxima 
Calvert, and a large population of N ehalennia gracilis Morse. 
Williamsonia lintneri (Hagen) 
Specimens examined — An exuvia from a nymph which emerged 
in captivity and twelve exuviae collected 2 May - 9 May 1970 at 
Ponkapoag Bog, Blue Hills Reservation, Norfolk County, Massa- 
chusetts. 5 
Description — Body length 17-18 mm, width of the abdomen 7.5 
mm. In general appearance the nymph is light brown in color and 
practically devoid of prominent setae except on the hind margin of 
abdominal segment 9 and on the hind tibiae. The dorsum of the 
abdomen is speckled with small spots of darker pigmentation and a 
narrow stripe of lighter pigmentation extends down the dorsal ridge 
(Figure 1). The wing sheaths extend to the base or middle of 
abdominal segment 6. Dorsal spines are present on abdominal seg- 
ments 3 through 9. In profile (Figure 2) they are rather small 
and project posteriorly. Lateral spines are present only on abdomi- 
nal segment 9 where they form about one-third of the lateral margin 
of that segment. Setae along the posterior margin of segment 9 are 
about twice as long as the lateral spines. 
There are seven antennal segments. There are no dorsal horns 
on the head. The labium is as shown in Figure 3. Premental setae 
(terminology of Corbet 1953) usually number 12 + 12 but a 
range from 11 + 11 to 12 + a i2 was observed. The even spacing 
of the 8 palpal setae on each palpus is interrupted slightly between 
5 Of these specimens seven have been distributed to the following institu- 
tions and investigators: Florida State Collection of Arthropods, Gainesville, 
c/o Dr. Minter J. Westfall, Jr.; Royal Ontario Museum, Toronto and The 
Canadian National Collection, Ottawa, c/o Dr. Philip S. Corbet; The U. S. 
National Museum, Washington, D. C., c/o Dr. Oliver S. Flint, Jr.; The 
University of Michigan Museum of Zoology, Ann Arbor, c/o Mrs. Leonora 
K. Gloyd ; G. H. and A. F. Beatty, State College, Pennsylvania; and the 
Museum of Comparative Zoology, Harvard University, c/o Dr. Howard 
Evans. 
