AXDRENFD.E. 227 



valve. The colour of the pubescence in fresh examples, 

 wliich is nearly always brighter in the ? than in the ^, 

 affords good characters, but it fades quickly after exposure 

 to the weather, and is reduced by degrees to a general 

 grey. The colour aud distribution of the pubescence is also 

 seriously afiected by the presence in the abdomen of the 

 little parasite Stylops, which frequently attacks some of 

 the species. Professor Perez, of Bordeaux, has given an 

 excellent account of the habits of the parasite in relation to 

 Andrciia in his " Des Effets du Parasitisme des Stylops, &c.," 

 published in the Actes de la Soc. Linn, de Bordeaux, 

 1886. As a rule, the presence of the parasite may be 

 known by the protrusion of its head between the segments, 

 or by the distorted and often inflated appearance of the 

 abdomen, but there ai-e cases where the parasite has affected 

 the appearance of the bee by its effect on the larva, and 

 has escaped during the final change. The parasite 

 enters the bee in its larval state, and more or less 

 affects the genital organs ; it may not render them abortive 

 or useless, and in some cases, according to Mr. R. C. L. 

 Perkins' observations, may affect them very slightly, but 

 the results which chiefly concern the Hymenopterist all 

 tend towards the assimilation in outward appearance of the 

 two sexes, which goes a long way to show that they must 

 be due to effects on the generative system. If a ^J be 

 affected its head tends to become smaller, the pubescence 

 of the abdomen to become denser and to form paler apical 

 bands, the legs to become more densely hairy, and in 

 species which have a white clypeus this is liable to 

 become black in part or altogether ; in a ? the head also 

 tends to become smaller, but the scopa? to become less 

 dense and paler, as also the pubescence of the abdomen, 

 but, as in the cJ, it tends to form pale apical bands; in 

 species where the c? has a white clypeus the stylopized ? 

 often has it white or partly white; there is also often an 

 immature look about stykipizud specimens of cither sex. 



