NO. II NAIADS OF DRAGONFLY GENUS PLATHEMIS—LEVINE 23 
shape of the dorsal abdominal hooks. Needham states that the dorsal 
hooks in both species are present on abdominal segments 2-6. Garman 
(1927), in his description of Plathemis lydia, states that the dorsal 
hooks are present on segments 3 to 5 or 6. The present writer’s ob- 
servations on 25 naiads of P. lydia from Amherst, Mass., and 6 
exuviae of P. subornata from Ana Springs, Oreg., are not in con- 
formity with those of either Needham or Garman. The writer has 
found that in both species the dorsal hooks occur always and only on 
segments 3-6, 
In Plathemis lydia the dorsal hooks are present on abdominal seg- 
ments 3 to 6, the longest being on segment 5. They are all posteriorly 
curved, sharp and thornlike, and covered with spiniform setae (fig. 
24). 
In P. subornata the dorsal hooks are also present on abdominal seg- 
ments 3 to 6, the longest also being on segment 5. In this species, 
however, the dorsal hooks differ from those of P. lydia in being blunt 
and hairy (fig. 25). 
TAXONOMY AND DISTRIBUTION 
GENERIC CHARACTERS: The naiads of the genus Plathemis Hagen 
(1861) can be separated from all other odonate naiads by the follow- 
ing characters: 
1. Naiads without caudal gills, with small spinose appendages at apex of 
PEDOMETER toate) aiaisia Sia ereiaumieits essa e%s' aay Suborder Anisoptera—DRAGONFLIES 
2. Labium forming a deep spoonlike mask covering face up to antennae; distal 
edge of labial palpus evenly and regularly toothed; ligula never with two 
large teeth at middle of distal margin................ Family LipELLULIDAE 
3. Head without frontal horn; lateral spines of abdominal segment 8 shorter 
than length (along sagittal line) of segment 9; no dorsal hook on abdominal 
ERIM NG 1 ck aisibs owas sicia't oi aieiainis albjniela, wi siatelelete Subfamily LIBELLULINAE 
4. Eyes capping anterolateral angles of head, more frontal than lateral; abdomen 
lanceolate in outline, gradually narrowed to apex...... Tribe LIBELLULINI 
5. Ligula of labium crenulate on distal margin; labial palpi each with ro lateral 
setae; prementum with 8 setae. Abdomen with dorsal hooks on segments 
3-6, and small lateral spines on segments 8 and 9; paraprocts twice as 
PEIN ASUCCECES fa OL LR SG as He Shaw TU ates Ose iteld BUatoeme Genus Plathemis 
SPECIFIC CHARACTERS: The mature naiads of the two known spe- 
cies of the genus Plathemis can be separated as follows: 
Dorsal abdominal hooks on segments 3-6, all sharp and thornlike and bearing 
MENTE RGEC Fos Cine eo hes Sb wo or tis du. eicaee ate tamar spe eed h getee ms P. lydia 
Dorsal abdominal hooks on segments 3-6, all blunt and hairy...... P. subornata 
