1939] 
Mosquitoes of Massachusetts 
115 
Larvse 
1. Thorax narrow with distinct segmentation; prolegs 
on the first 2 abdominal segments ; tracheae ending in 
a pair of discs on eighth abdominal segment (Fig. 
21) : Dixinse 
Thorax distinctly broader than abdomen, without dis- 
tinct segmentation, paired prolegs lacking t_2 
2. Antennae prehensile, with long and strong apical spines 
(Fig. 17) : Chaohorinse 
Antennae not prehensile (Fig. 8) : Culicinte 
Subfamily Dixinse 
This group is represented by the single genus Dixa. 
Key to the Genus Dixa 
Adults 
1. Tips of hind tibiae noticeably enlarged, deep black, 
sharply contrasting with the remainder of the mem- 
ber; wing veins with clouded margins; proboscis 
black, halteres yellowish, scutellum fuscous testa- 
ceous ; terminal clasper segment tapering, mesal pro- 
cess of the basal segment simple, elongate: clavata 
Tips of hind tibiae not so sharply differentiated 2 
2. Petiole of R2+3 (measured on a straight line from its 
base to base of fork) less than % as long as R 3 ; pro- 
boscis, scutellum, and knob of the halteres yellow; 
crossvein of wing very feebly clouded, r-m crossvein 
slightly distad of the base of R4+5 : terna 
Wing with other characters 3 
3. Wing with one distinct spot 4 
Wing spot very indistinct or wanting 5 
4. Petiole of R2+3 and R 3 subequal in length; proboscis 
and scutellum blackish : centralis 
Petiole shorter; proboscis and scutellum yellowish: 
- — — - notata 
5. Dorsum of the thorax as well as the upper part of the 
pleura black ; proboscis, halteres and scutellum dark : 
fusca 
Dorsum of the thorax yellowish with thoracic darker 
