52 BULLETIN 66, UNITED STATES NATIONAL MUSEUM. 



HYLECHTHRUS RUBI Saunders. 



Concerning this species Saunders (1852) contributes a very valuable 

 description of the exsertion of the head of the male from Prosopis 

 rubicola versicolor: 



I have not unfrequently been enabled to detect the eye shades of the parasite before 

 the Hylxus nymph has discarded its pellicle, working to and fro beneath the dorsal 

 tegument; although more conspicuous when the bee first attains the imago form, the 

 head of the parasite being then seen turning from side to side, and steadily pressing 

 all the while upon the rostrum, as the axis about which it revolves, in the ratio of 

 one-eighth of a circle, for the purpose of introducing this between the abdominal folds. 

 Thus when one eye shade advances the other recedes, both being carried deeper 

 below, when the great strain appears to operate upon the upheld rostrum. As soon as 

 the lodgment is effected, this is gradually pushed forward by a continuation of the 

 same process, until sufficiently advanced, the entire operation occupying from one 

 hour in some cases, to two hours in others, and immediately following the ultimate 

 transformation of the bee in its then moist state; after which the parasite remains 

 perfectly motionless. I have sometimes seen parasites thus engaged simultaneously 

 within the same ITylxus; and should the attempt not prove successful, the locality is 

 changed for the segmental division next in succession; or, if foiled again here, the 

 parasite sometimes remounts to the preceding one. These efforts have been con- 

 tinued for upward of an hour after a newly developed imago Hylxus, within which 

 the eyeshades were discerned, had been emersed in spirits, until at length the parasite 

 appeared to have attained the extreme verge of the segmental threshold ere its career 

 was finally arrested. 



At the moment of protrusion the male head is white except the 

 eyeshades, but in a few hours the puparium assumes a light castane- 

 ous hue. The ordinary period for quitting the pupa-case would 

 appear to be the eighth day after the first protrusion. 



After the first burst, produced apparently by the parasite pressing forcibly against 

 the operculum, the head and shoulders being instantaneously protruded on this falling 

 off, a slight effort suffices to liberate the pseudelytra and first pair of legs; when all 

 these organs idly beating the air and agitating incessantly, much exertion is made to 

 effect a passage for the second pair of legs, where the principal detention occurs; 

 after which a few jerks up and down speedily serve to release the metathorax and 

 abdomen; the imago forthwith winging its flight toward the light. 



Saunders never succeeded in keeping the males alive beyond the 

 day of exit and rarely more than two or three hours. However, 

 during this brief life they may exert great strength, for one male was 

 seen to draw around the body of its dead host and two other males 

 which later came out. 



HYLECHTHRUS QUERCUS Saunders. 



In an unpublished manuscript Saunders estimates the term of 

 gestation at from three to four weeks. He found triungulinids on 

 June 3. 



HYLECHTHRUS SIEBOLDII Saunders. 



Saunders records triungulinids on July 5, 



