7 6 HYMENOPTERA 



CHAP. 



individuals of which have the habit of rolling themselves up in a 

 ring ; while, as the calibre of the tube is but small, they are 

 unable to straighten themselves and move about, so that their 

 consumption in proper order is assured. Some interesting 

 points in the habits of an allied species, 0. (Pterocheilus*) srjinipes 

 have been observed by Verhoeff ; the facts as regards the con- 

 struction and provisioning of the cell are almost the same as in 

 0. reni/orniis. The species of Odynerus are very subject to the 

 attacks of parasites, and are, it is well known, destroyed to an 

 enormous extent by Chrysididae. Verhoeff says that the wasp 

 in question supplied food much infested by entoparasites ; further, 

 that a fly, Argyromoeba sinuata, takes advantage of the habit of 

 the Odynerus of leaving its nest open during the process of pro- 

 visioning, and deposits also an egg in the nest ; the Odynerus 

 seems, however, to have no power of discovering the fact, or more 

 probably has no knowledge of its meaning, and so concludes the 

 work of closing the cell in the usual way ; the egg of the 

 Argyromoeba hatches, and the maggot produced feeds on the 

 caterpillars the wasp intended for its own offspring. Verhoeff 

 observed that the egg of the wasp-larva is destroyed, but he does 

 not know whether this was done by the mother Argyromoeba or 

 by the larva hatched from her egg. Fabre's observations on 

 allied species of Diptera render it, however, highly probable that 

 the destruction is effected by the young fly-larva and not by 

 the mother-fly. 



Mr. E. C. L. Perkins once observed several individuals of our 

 British 0. callosus forming their nests in a clay bank, and pro- 

 visioning them with larvae, nearly all of which were parasitised, 

 and that to such an extent as to be evident both to the eye and 

 the touch. In a few days after the wasps' eggs were laid, swarms 

 of the minute parasites emerged and left no food for the Odynerus. 

 Curiously, as it would seem, certain of the parasitised and stored- 

 up larvae attempted (as parasitised larvae not infrequently do), 

 to pupate. From which, as Mr. Perkins remarks, we may infer 

 that (owing to distortion) the act of paralysing by the wasp had 

 been ineffectual. Mr. Perkins has also observed that some of the 

 numerous species of Hawaiian Odynerus make a single mud-cell, 

 very like the pot of an Eumenes, but cylindrical instead of 

 spherical. This little vessel is often placed in a leaf that a 

 spider curls up ; young molluscs of the genus Acliatinella also 



