164 THE AMERICAN NATURALIST [Vol. XL VIII 



the upper side of grass blades, others more or less con- 

 cealed in the rolled up young leaves (Shull, 1911). I have 

 found, however, that among the adults, those in exposed 

 situations are almost exclusively females, while those in 

 the rolled young leaves are either males or females. (For 

 the first time on record, the males of this species, as will 

 be shown in the second part of this paper, have been found 

 in considerable numbers.) The larvae, according to my 

 observations, may be either exposed or concealed; the ex- 

 posed ones are predominantly the older larvae. 



In one of the grasses (Spartina michauxiana) on which 

 Anaphothrips was found in abundance at Douglas Lake, 

 Michigan, the leaves bear on the upper surface a set of 

 fine, but prominent, ridges running parallel to the axis of 

 the leaf. Adult females and larvae of Anaphothrips on 

 the exposed parts of these leaves were always lodged be- 

 tween the tops of these ridges, and almost invariably 

 with their heads toward the base of the leaf. If disturbed, 

 they began to crawl along the crest of one of these ridges 

 toward the base of the leaf. It was possible to force them 

 to turn in the opposite direction, but if allowed to do so 

 they soon turned again toward the base of the leaf, often 

 continuing until they were among the rolled young leaves 

 in the center of the top of the plant. 



Anthothrips verbasci is found exclusively on one spe- 

 cies of plant, the common mullein (Verbascum thapsus). 

 Furthermore, it is rare that a specimen of mullein, of con- 

 siderable size, is found free from the mullein thrips. Most 

 of the thrips are found among the florets or seed pods of 

 the spike. Less commonly they are to be seen on exposed 

 surfaces, as on the leaves or stem lower on the plant; but 

 these exposed individuals are mostly adults. The larvae 

 are usually hidden on the flower spike unless that situa- 

 tion is crowded by a large number of larvae ; and the larva 

 that are occasionally found exposed are mostly nearly 

 fully grown. 



Anthothrips niger was not abundant enough during my 

 stay at Douglas Lake that many observations of its 



