March 1S94.J 



PSYCHE. 



41 



Stelis miniita Nyl. (Zool. anzeiger, 

 vol. XV. 1S93, pp. 41-43). 



Tliis species was found to be para- 

 sitic ill the nests of Osmia leucorne- 

 laetia Kirby which constructs its cells 

 in hollow twigs. Dr. Riley's summary 

 of this species is as follows : — 



At tlie bottom of the cell the female Osmia 

 first puts a layer of pollen wliich is to serve 

 as food for the nearly full grown larva. 

 Above this pollen, the bee commences to 

 store the cell with prepared bee-bread. At 

 this moment the female Stelis watches her 

 opportunity to lay an egg in the Osmia cell, 

 the egg thus being always near the bottom 

 (posterior end) of the food mass. Unaware 

 of the presence of the parasite egg, the 

 Osmia female continues her work, and, after 

 nearly filling the cell, deposits her own egg 

 on the top (anterior end) of the food mass. 

 The cell is then closed with a layer of 

 macerated particles of plants and a second cell 

 prepared above the first. The Stelis larva 

 hatches but little earlier than that of the 

 Osmia, and both larva feed on the food- 

 mass, the parasite larva at the bottom, the 

 host larva at the top. The latter remains 

 stationary at the top and grows very slowly; 

 the parasite larva grows more rapidly, and 

 gradually works its wa}' upward through the 

 food-mass, thus gradually approaching the 

 Osmia larva. The crisis finally comes; the 

 Stelis larva encounters the Osmia larva — a 

 short but deadly combat ensues — the Osmia 

 larva is easily overpowered and killed by 

 the much larger and stronger parasite, and 

 its body is devoured by the latter within one 

 or two days. 



The genus Bpeolus is stated by our 

 American authorities to be parasitic in 

 the cells of Colletes, evidently based 

 upon an observation of an English 

 authority, Shuckard, who claims to 

 have bred Epeohis variegatns from 

 the cells of one of these bees. 



This statement must, however, be 

 erroneous, as it does not agree with 

 observations of mine made on a com- 

 mon American species. It was evi- 

 dentl}- based upon insufficient data, 

 just as was found to be the case re- 

 pecting St. Fargeau's statement about 

 Sphecodes being parasitic in the cells 

 of Halictus. 



The past summer, while in Missis- 

 sippi, I was fortunate enough to 

 stumble upon several specimens of 

 Epeohts donatus Smith making their 

 burrows, and I am thus enabled to 

 assert that this species is not parasitic 

 but builds cells and deposits honey- 

 paste for its offspring, just as many 

 other solitary bees. My observations 

 throw grave doubts upon the I'eliabilitv 

 of Shuckard's statement and lead me 

 to believe that he had cells of both 

 Epeolus and Colletes mixed together 

 in his breeding jars, when his speci- 

 mens were reared. 



On the plantation where I was stay- 

 ing, near Utica, Miss., Epeolus dona- 

 iiis was oljserved making its burrow 

 in hard cla\', beneath a cotton-gin 

 shed, into which I had run to escape 

 a passing rain storm which came on 

 suddenly, while I was investigating 

 cotton-insects in a cotton-field near by. 

 My attention was first attracted by 

 the buzzing of the bees ; for, as they 

 returned from the field to enter their 

 burrows, before alighting they invari- 

 ably made several circles above the 

 mouth of their burrow, all the time 

 making a verv loud humming or buzz- 

 ing noise, very noticeable and which 

 ceases only as they reach the ground. 



