50 



THE GUIDE TO NATURE 



egg- on the bee-bread (a mixture of nec- 

 tar and pollen). At last the nest is defin- 

 itely closed by its owner {Collet cs culo- 

 phi) and both bees disappear to return 

 no more. 



Another parasitic bee (Stclis uiacii- 

 lata) lays her eggs in the nests of Alci- 



FIG. 2. DIAGRAMS OF SECTIONS OF CELLS. 



A. Diagram of a section lengthwise through a 

 cell troni the nest of Alcidamea prodncta: c, egg of 

 host bee, Alcidamea producta; d, egg of parasitic bee, 

 Stelis sexmaculata. 



B. Diagram of section lengthwise through lower 

 half of cell of Megachile latimanus: e, egg of host 

 bee, Megachile latimanus; f, egg of parasitic bee, 

 Coelioxys rufitarsis. Notice that the egg of 

 the parasitic bee is concealed on the side of the mass 

 of bee bread. (After Graeniclier). 



damea producta. The nest of Alcidamea 

 producta is a tunnel in the pith of the 

 dry stem of the blackberry or sumac. At 

 the bottom there is stored a conical mass 

 •of bee-bread on the top of which Alci- 

 damea lays her egg; during the absence 

 of the host-bee the parasite Stelis enters 

 the tunnel and lays an egg on the side 

 near the base of the bee-bread. (Fig. 2). 

 The host-bee may build as many as four 

 such cells, one over the other, closing 

 each with a felt-like mass of chewed 

 strawberry leaves. 



Let us now enter the nest and observe 

 the tragic end which awaits the rightful 

 heir. According to Dr. Graenicher both 



B 



FIG. 3. MANDIBLES OF LARVAE. 



A. Mandible of larva of host bee, Alcidamea pro- 

 ducta. Notice that it is blunt and bifid, adapted 

 neither for attack nor defense. 



B. Acutely pointed mandible of larva of parasitic 

 bee, Stelis sexmaculata, with which it pierces the body 

 of the host larva. (After Graenicher). 



eggs hatch at nearly the same time. The 

 larva of the parasite is armed with long- 

 sharp mandibles; but those of the host 

 larva are blunt and bifid and not well 

 adapted either for defense or attack — so 

 the latter is doomed from the beginning. 

 When the two larvae meet, while feed- 

 ing on the bee-bread, the parasite seizes 

 the body of the host-larva between its 

 sharp mandibles. The latter may strug- 

 gle a little but soon succumbs ; after 

 sucking out the liquid contents of its 

 host the parasite resumes feeding on the 

 bee-bread. If the host bee lays two eggs 

 in the same cell, the larvae can not injure 

 each other; but if there are two larvae 

 of the parasite a combat is certain to re- 

 sult, and the victor is the larva obtaining- 

 the first hold on the body of the other. 



The handsomest parasitic bees belong 

 to the genus Nomada, and Smith calls 

 them most beautiful of all the genera 

 found in Great Britain. They are often 

 called wasp-bees, "because of their gay 

 coloring." They are dark red in color, 

 often sufifused partially with black, and 

 maculated with bright or pale yellow (a 

 yellow streak is certainly a fitting color 

 for these bees). The males are much 

 jTiore yellow than the females. As the 

 females no longer .gather pollen they 

 have largely lost the hair brushes used 

 for this purpose. They lay their eggs 

 in the burrows of the ground bees (An- 

 drciia). They occur chiefly north of the 

 equator, and are more abundant in west- 

 ern than in eastern North America. 



In New England there are two species 

 of false bumblebees, of the genus Psithy- 

 rus, which live in the nests of the bum- 

 blebees. In appearance they closely re- 

 semble bumblebees, and are no doubt de- 

 rived from the same ancestral stock. 

 They produce no workers, only males 

 and females, which would appeal to a 

 certain type of socialists as an ideal state 

 of afifairs. They were long supposed to 

 be merely commensals, living with the 

 bumblebees but doing no harm. Their 

 economy, however, has recently been 

 fully described by Sladen. The female 

 Psithyrus attacks and kills the bumblebee 

 queen and takes possession of the nest ; 

 but with cunning foresight she waits un- 

 til a sufficient number of eggs have been 

 laid to provide a force of bumblebee 

 workers large enough to provide for her- 

 self and her brood. Sometimes she waits 

 too long and enters a colony with a 

 strong company of workers, and is fu- 



