343 
1986 ] Wheeler & Wheeler — Larvae of Eciton 
preparation of these immature was the most difficult we have ever 
experienced. 
II. Interspecific Differences 
Whenever we have had two or more species in the same genus, we 
have either given a complete description of each or at least men- 
tioned differences. We have not been willing to go beyond that, 
because we did not know the extent of intranidal or internidal or 
intraspecific differences. Here at last, we have series of Eciton bur- 
chelli and E. hamatum which embolden us to make a tentative 
comparison. Table 1 gives a few characters which can be measured 
for each instar in each species. The “spiracle diameter” which we 
have not mentioned previously, is the diameter of the atrium and 
not of the opening into it. 
Eciton burchelli Westwood 
Figure 1 
Egg. About 0.3 X 0.54 mm. 
First Instar Larva. Length 0.59-0.9 mm long (average 0.73 
mm). Head greater in diameter than body which tapers to the poste- 
rior end. Anus subterminal. Segmentation distinct. Spiracles about 
0.001 mm in diameter. Entire integument sparsely spinulose, the 
spinules minute and isolated. Body hairs lacking. Cranium subcircu- 
lar. Antennae minute, just above midlength of cranium. Head hairs 
lacking. Labrum arcuate, about 1/4 width of cranium; with a few 
spinules and sensilla on and near ventral surface. Mandible with 
straight apical tooth which is feebly sclerotized, remainder not 
sclerotized. Maxilla broadly paraboloidal and appearing adnate; 
palp represented by 7 sensilla in a loose cluster; galea represented by 
2 sensilla. Labial palp represented by 3 sensilla; opening of sericter- 
ies a short transverse slit. 
Second Instar Larva. Length (through spiracles) 0.9- 1.5 mm 
(average 1.2 mm). Head same diameter as T1 and AV, the widest 
parts of the body. Spiracles about 0.003 mm in diameter. Entire 
integument spinulose, the spinules moderately abundant and iso- 
lated. Body hairs 0.006-0.012 mm long; few, most on Tl, fewer on 
T2 and T3. Cranium subhexagonal; integument with a few spinules. 
Antennae just above midlength of cranium. About 30 head hairs; 
