_T._ (_Larrada_) _australis_, according to Whittell, plays the part of a burglar, breaking open the cells of _Pelopaeus_ (_Sceliphron_) _laetus_ after they have been completed and stored with spiders; it then takes possession of the cell, and curiously enough the _Pelopaeus_ permits this, although the cell contains its egg and the store of food that is intended for the use of its own young. To us this seems very strange, but it is probable that the _Pelopaeus_ has no idea of the consequences of the intruder's operations; {118}it being one of the strange facts of nature that these highly endowed creatures never even see the offspring for whose welfare they labour with such extraordinary ingenuity and perseverance. Neither can we suppose that they have a conception of it derived from a knowledge of their own individual history; for their very complete metamorphosis is scarcely reconcilable with any such recollection on their part. It may possibly therefore be the case that, having no idea whatever of the offspring, they are equally destitute of any conception that it will be destroyed by the operations of the _Larrada_. However this may be, Whittell informs us that both wasps skirmish about for a little as if each were mistrustful and somewhat afraid of the other; this ends by the _Pelopaeus_ withdrawing its opposition and by the _Larrada_ taking possession of the cell, which it then proceeds to divide into two, using for the purpose of the partition portions of the material of the nest itself; possibly it is only a contraction of the size of the cell, not a true division, that is effected; however this may be, after it is accomplished the _Larrada_ deposits its own egg in the cell, having, it is believed by Whittell, previously destroyed that of the _Pelopaeus_. Judging from what occurs in other species it is, however, more probable that the destruction of the egg or young of the _Pelopaeus_ is carried out by the larva of the _Larrada_ and not by the parent-wasp. From a remark made by Maindron as to the proceedings of _Larrada modesta_, in Ternate, it seems probable that its habits may prove to be similar to those of _L. australis_, for it frequents the nests of _Pelopaeus_ after they have been completed. SUB-FAM. 4. TRYPOXYLONIDES.—_Differ from Larrides by the inner margin of the eyes being concave, and the marginal cell not appendiculate. (In_ Trypoxylon _there is only one distinct submarginal and one distinct discoidal cell, a second of each being indicated faintly.)_