131 



circumstances as well as the ease with which thej are collected, 

 when considered in connection with the sparseness of individ- 

 uals, rendered it almost certain that they would be subject to 

 the attacks of parasites. It was also certain that these para- 

 sites when discovered would be of small size and that a mod- 

 erate sized Ichneumonid or Braconid was not to be looked for, 

 since none such (other than can be otherwise accounted for) 

 are to be found in the haunts of Rhyncogonus throughout the 

 islands. Through Mr. Giffard's perseverance, we are now able 

 to say that one check, and no doubt a very important one, to the 

 multiplication of Rhyncogonus blackhurni is an egg-parasite of 

 the genus Ewpelmus, the species being previously undescribed. 

 From the specimens of egg-masses of the beetle submitted to 

 me by Mr. Giffard, from which two of the parasites had 

 emerged, I suspect that one egg affords sufficient food for one 

 parasite, though the latter is of large size for the amount of 

 nutriment that it would thence obtain. When I exposed these 

 egg masses by separating the koa leaves, which were very firmly 

 glued together and concealed them, in both cases I found the 

 remaining eggs, together with some dead larvae of the beetle, 

 to be covered with a mass of minute Acari, which had partially 

 devoured them, as also several still immature pupae of the 

 Eupelmus. The attacks of Acarids are frequently a cause of 

 great trouble in rearing insects in captivity in these islands, 

 but seem to be of conparatively small account under natural 

 conditions. The two parasites, that had emerged from one of 

 the egg-masses had escaped by the same round hole gnawed 

 through the Acacia leaf. The other eggs-mass had also been 

 parasitized, but the contents all destroyed by the Acarids. 

 Probably the Eupelmus, like some other egg-parasites, will only 

 attack the eggs when comparatively freshly laid, and the ex- 

 tremely wet weather would sufficiently account for the fact 

 that not more of the egg-masses, exposed to parasitic attack by 

 Mr. Giffard, were parasitized. ISTo doubt, in many of the 

 eggs experimented with, embryonic development had already 

 advanced too far before their exposure to parasites. It is note- 

 worthy that the one egg-mass found under natural conditions 

 yielded parasites only. 



The Hawaiian species of Eupelmus are numerous, and the 

 parasite of Khyncogonv^ is one of the smallest of these. The 

 genus as represented in the islands is very remarkable for the 

 diversity in habits of the different species. One is known to 

 be parasitic on Coleopterous larvae (Anobiidae), one has been 



