SOLITARY WA^PS OF GENUS SYNAGRIS ROUBAUD. 523 



fection of this maternal instinct, so highly developed in the species of 

 Synagris of the group to which cornuta belongs, in this instance 

 spread the inauspicious influence of an isolated case of parasitism 

 over the whole nest, with disasterous results. 



In Synagris cornuta the instinct, though so much perfected, is 

 inferior, from this point of view at least, as compared with that of 

 the other species which do not follow the practice of feeding the 

 larvae from day to day in a manner so complete and exclusive. On 

 the other hand, the ordinary provisioning, consisting of blindly 

 burying the ^^'g in the midst of a quantity of food without care of 

 any kind on the part of the mother, also presents, as we have seen, 

 other disadvantages. It is an indirect parasitism which in turn 

 produces unforeseen effects. The caterpillars employed for provi- 

 sioning may be infested by Tachina-flies, and hence unavailable as 

 food for the larva of the Synagns^ which is condemned to perish, not- 

 withstanding the deceptive mass of provisions with which it is sur- 

 rounded. 



Another parasite, less common than the last, which has thus far 

 been observed only in the nests of S. cornuta^ is a magnificent species 

 of beetle of the family RhipipJioridce^ which is also a mortal enemy 

 of the laiwfE of this wasp. At present I do not know at what time 

 it penetrates into the cell and begins to attack its prey. Probably 

 it waits until the wasp walls up the cell and feeds on its host only 

 when the latter has ceased to have recourse to the maternal care. 



Finally, the adults themselves may be parasitized by the larvae of 

 Chalcis-flias (small parasitic hymenoptera) . I observed at Brazza- 

 ville for more than three months a female of Synagris cornuta be- 

 longing to a, nest Consisting of a single cell, which remained in its 

 nest without laying eggs, until one day I saw emerge from the ex- 

 tremity of the abdomen, which extended outside the nest, a small 

 white active larva. A few moments later another larva appeared, 

 and, like the preceding one, dropped to the ground. I then captured 

 the Synagris and discovered by dissection that the whole body cavity 

 was infested by small larvae similar to the first ones, which were 

 doubtless prepared to escape by perforating the articular membrane 

 of the posterior segments. These larvae (pi. 4, fig. 3) were charac- 

 terized by the presence of four pairs of retractile pseudopods on seg- 

 ments 5 to 8 of the body. I was unable to ascertain the adult form. 

 The larvae were transformed into pupae in a small cocoon soon after 

 leaving the body of the host, but they did not emerge. 



A noteworthy fact in tliis instance was the sterility of the parasi- 

 tized wasp. It was observed to be incapable of laying eggs, and dis- 

 section showed that the ovaries remained in a state of immaturity. 

 This was a clear case of parasitic castration. No doubt other para- 



