SUBFAMILY MESEMBRINELLINAE 15 
mented areas and toward anterior ventral third with pigmented 
sclerotized plate; sixth to eleventh segments each posterodorsally 
and posteroventrally with narrow spinose bands, strong anterior 
spinose bands posteroventrally, the individual spines long and 
black in more mature specimens; ventral pad on the eleventh 
segment with weak spines in younger specimens, but strong, 
black and hooklike in more mature specimens; spines around 
posterior cavity long and hairlike; anal protuberance and 
ventral view of posterior portion (pl. 32, F and G), as illus- 
trated. Posterior cavity shallow, the ventral margin with six 
weak tubercles, the dorsal margin with eight tubercles. Meta- 
pneustic; posterior spiracles (pl. 32, H) in early part of instar 
each with two slitlike apertures, these partially joined ventrally; 
in more mature specimens the plates separated by one-fourth the 
width of one plate, each plate more or less heart-shaped and with 
two distinct slitlike, nearly horizontal apertures; peritreme very 
weak and hardly apparent dorsally but strong around the button 
area. Cephaloskeleton (pl. 32, E) weakly developed in very 
young larvae but more heavily sclerotized and pigmented in 
more mature specimens; labial sclerites divided at tips but united 
basally, elongate and strongly hooked; hypostomal sclerite very 
short; pharyngeal sclerite weakly pigmented, the dorsal cornua 
short, weakly sclerotized except at dorsopharyngeal area, the 
ventral cornua without longitudinal grooves or furrows, 
elongate, weakly sclerotized; no accessory sclerites. 
It was impossible to determine whether one or two instars 
are included in the above description. All the larvae at hand are 
metapneustic, a condition usually considered indicative of first- 
instar development. The smallest larvae are 3 mm: in length, the 
largest larvae fully 14 mm. It is difficult to understand how 
sclerotized parts of a single instar could attain the extremes 
exhibited by these larvae. It may be that the larva of this species 
is deposited nearly ready for molting into the third instar and 
the free larval stage is therefore a very short one; perhaps this 
is a necessity in the tropics. 
Huascaromusca flavicrura (Aldrich), new combination 
Mesembrinella flavicrura Aldrich, U.S. Natl. Mus. Proc. 66(18) : 
16, 1925. (Type, male from La Suiza de Turrialba, Costa 
Rica, in A. L. Melander’s Collection.) 
A blue-black species with orange head and appendages. 
Male. Head width 13.6; length at antenna 6.4, and at vibrissa 
6.0; eye height 10.0; head height 12.0; bueca 0.12 of eye height, 
orange, with golden pollen, and with only black hair before the 
