142 HYMENOPTERA. 



spines on the upper and posterior edge of the orbit, which arc 

 also found in the pupa of Stigmus, a Crabronid genus, and which 

 evidently aid in locomotion. Thus the same law of degrada- 

 tion obtains in these highly organized bee-parasites as in the 

 lower parasitic species, though in a much less marked degree. 



From specimens found in the nests of Andrena and Halictus, 

 collected at Salem by Mr. J. H. Emerton, and now in the Mu- 

 seum of the Essex Institute, we have been enabled in great 

 part to clear up the history of this bee. We have found in the 

 nests of Andrena vicina both sexes of Nomada imbricata Smith, 

 and several females of Nomada palcheUa of Smith ; and in the 

 cells of Halictus parallelus Say, specimens of Nomada imbri- 

 cata. Both full-grown larvae and pupae of different ages, up 

 to the adult Nomada, ready to take leave of its host, were 

 found in the cells of the Andrena vicina. It seems, there- 

 fore, that the newly hatched young of Nomada must feed 

 on the pollen mass destined for the Andrena. But there 

 seems to be enough for both genera to feed upon, as the young 

 of both host and parasite were found living harmoniously to- 

 gether, and the hosts and their parasites are disclosed both at 

 the same time. Does not this mild sort of parasitism in No- 

 mada throw much light on the probable habits of Apathus, the 

 Humble-bee parasite? It is more than probable that the Apa- 

 thus larvae simply eat the food of the Bombus larvae, and do 

 not attack the larvae of their hosts. Both Nomada and Apathus 

 in their adult stages live harmoniously with their hosts, and 

 are seen gathering food from the same flowers, and flying about 

 the same nest. 



In the second subfamily, Andrenetce , the ligula, or tongue, is 

 for the most part short and broad, and the maxillary palpi 

 have four joints of equal size. 



In Sphecodes the body is smooth and wasp-like, and in its 

 habit of running and flying in dry sandy places, it resembles 

 Sphex, whence its generic name. The abdomen is generally 

 light red, farther aiding in the resemblance to the Spliegidw . 

 The ligula is short, lancet-shaped, fringed with setse ; the para- 

 glossae are not so long as the tongue, while the labial palpi are 

 shorter than the paraglossae, and the maxillae are broad, lan- 

 ceolate, with six-jointed palpi. The antennae of the males are 



