June, 1897 1 1 ACKARD : I RANSFORMATIONS OF HYMENOPTERA. 
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abdominal segments which are nearly smooth and very round. The 
specimen described was not fully grown and was found by Mr. J. H. 
Emerton, August 13, with eggs of the second brood. 
When the larva has voided all its excrement the tubercles over the 
whole body become very prominent, extending from low down on the 
side of the body, forming high, regular, very prominent transverse 
ridges, which beneath the abdomen are more prominent than on the in¬ 
side of the thorax. Length, .40 inch. 
In examining the larvae of H. parallels and H. ligatus the head 
only differs, so far as one can tell, by the sides of one species bulging 
out; in the mandibles of H . ligatus being longer and slenderer, and 
the notch below being longer and ending in a distinct seta.' The head 
in the two species is of about the same size; the clypeus is of the same 
shape, the head above being a little more divided in H. parallels than 
in H. ligatus. The entire larva of H. ligatus is much longer and 
slenderer than that of H. parallelus , and the thickened tuberculous 
portion of the segments inclined to be a little more prominent. These 
differences are sufficient to produce changes in form, rendering the 
identification of the larva easy, but the best specific characters are the 
differences in size and slenderness of form. The larvae being just in 
the period approaching the semi-pupa stage, the head is protruded and 
the segments more or less elongated, as the parts of the pupa growing 
beneath press out the larval skin in various directions. The ovipositor 
can not be detected beneath the thin larval skin. 
1 his larva (the following description applies to it when in the early 
semi-pupa stage, and there are no hairs yet developed) differs from that 
of Andrena vicina in being longer and slenderer in proportion. The 
antennae are shorter, stouter and more clavate. The mandibles in this 
stage are not corneous. The maxillae are shorter, the lingua much 
longer than the tips of both pairs of palpi, which are of the same length 
as in Andrena. The two tubercles behind the ocelli are unusually 
prominent. Of the three ocelli, which are arranged at points in an 
equilateral triangle, afterwards becoming a very slight curved line, the 
middle one in front is not raised. 
In front of the ocelli, arranged transversely in a slight curved line, 
are four low, flat tubercles which resemble the ocelli; these disappear 
when the pupa becomes mature. The head and front, including the 
clypeus and labrum, are as in Andrena , but the supra-clypeal region in 
the specimen before me is better marked. The legs are a very little 
slenderer, and the hind tarsi do not reach nearly to the tip, but only 
half way, as the abdomen is much less elongated than in Andrena. 
