2. N0J1ADA. 109 



labium, the basal joint as long as the other joints united ; the second 

 about one fifth of the length of the basal joint; the two following 

 short, the apical one shortest. The maxillary palpi 6-jointed, the 

 basal joint short and subclavate, the second longest, the third a little 

 shorter than the second, decreasing in length to the apical joint. 

 Thorax ovate ; the scutellum more or less distinctly bituberculate ; 

 the anterior wings with one marginal and three submarginal cells, 

 the first as long as the two following united, the latter receiving 

 each a recurrent nervure about its centre ; the legs simple in both 

 sexes. Abdomen ovate, its apex truncate in the females, and acute 

 in the males. 



The bees belonging to this genus are popularly known by the 

 name of Wasp-bees, from their close resemblance in their gay 

 colouring to the smaller species of Vespidae ; they are, however, true 

 bees, and constitute the most beautiful of all the genera found in 

 this country. Xot withstanding the generally received history of their 

 economy, we shall search in vain for much precise information. In 

 the ' Entomological Magazine ' we learn that they deposit their eggs 

 in the nests of other bees at the time when the working bees deposit 

 theirs, and that when hatched the larva, being stronger and larger 

 than the rightful possessor of the cell, consumes the food of its 

 companion and starves it to death : all this, however, is mere conjec- 

 ture ; the larva of these parasites must always be smaller than that 

 of the working bee. Xo one appears to know any thing beyond the 

 mere fact of their entering the burrows of Andrenida; and Apidae, 

 and of their being found in the cells of the working bees in their per- 

 fect condition. It is most probable that they deposit an egg on the 

 provision laid up by the working bee, that they close up the cell, and 

 that the working bee, finding an egg deposited, commences a fresh 

 cell for her own progeny. My reason for thinking it probable that 

 the parasite closes the cell, is that I have frequently captured 

 Nomada? and Melectce with masses of clay attached to their posterior 

 tibiae : and in the well-known genus of exotic parasitic bees, Crocisa, 

 specimens are of frequent occurrence which have masses of clay or 

 mixed earth on their tibiae ; this, however, requires, and is deserv- 

 ing of, further investigation. I have found several of the species 

 in the cells of Andrenidse ; these will be mentioned under the 

 respective species. One instance which throws some light upon the 

 economy of the genus may be recorded here. Some years ago, 

 in the month of June, I met with a large colony of Evcera longi- 

 comis, and observed great numbers of Nomada sexfasciata flying 

 about amongst the bees, and occasionally entering into and issuing 

 from their burrows. In the beginning of April of the following year 

 I visited the locality for the purpose of obtaining males of the 

 Nomada, as very few were found when the colony was first dis- 

 covered : the cells of Eucera were found at about the depth of eight 

 inches in a stiff clayey soil ; of these a considerable number were 

 obtained. On examination, many of the bees were found to be in the 

 pupa state, some far advanced towards their perfect condition, others 



