THYSANOPTERA AND ORTHOPTERA. 1S3 



this clear. One class of species, of which Thrips tabaci is typical, is to 

 be found in chinks and crevices of plants, almost everywhere if the tis- 

 sues are sufficiently tender. Among the florets of various compositae is 

 a favorite situation. A single flower of the common white yarrow (Achil- 

 lea millefolium) may harbor dozens of them, and one head of Canada 

 thistle (Cirsium arvense) has been known to contain over a hundred of 

 Euthrips tritici. Other flowers, if not large or open, furnish the right 

 location. One umbel of the common milkweed (Asclepias syriaca) con- 

 tained several hundred. But flowers are not alone in the hst. I have 

 found Thrips tabaci among the young buds and in tufts of small leaves 

 of burdock (Arctium mirius), among buds of boneset (Eupatorium per- 

 foliatum) and in young curled leaves of balsam-poplar (Populus balsatyi- 

 ifera). Other species Hve in narrow crevices in the bark of various 

 trees. 



More open and exposed situations, on the other hand, are the home 

 of other species. Thus, Anaphothrips striatus was found rather com- 

 mon on the upper side of the leaves of wild rye (Elymus canadensis) 

 and of sea sand-reed (Ammophila arenaria). On the former plants the 

 adults showed a shght preference for the curled portions of the leaves, 

 but many adults were also found wholly exposed, and the larvae were 

 about as abundant on the flat leaves as on the rolled one«. Specimens 

 of Ctenothrips bridwelli were found on the leaves of the star-flowered 

 Solomon's seal (Smilacina stellata), and PhyUothrips aspersus on leaves 

 of sweet-scented grape (Vitis vulpina), both without apparent attempt 

 at concealment. 



These examples are given, merely to indicate the character of the 

 places occupied by the different groups of species. The complete list 

 of plants is given for each species under the heading of "habitat" in the 

 annotated list of species. Those species which inhabit narrow crevices 

 I designate "interstitial"; those in exposed situations, "superficial". 

 These classes may be conveniently subdivided according to the scheme 

 given below. The species belonging to each class are indicated in their 

 proper places, arranged alphabetically, not taxonomically. 

 1. Interstitial, living in closely concealed situations, 

 a. Anthophilous division, dwelling in flowers. 



Aeolothrips fasciutus 



Anthothrips niger 



Anthothrips verbasci 



Chirothrips maiiicatus 



Euthrips tritici 



Euthrips juscus 



Scirtothrips ruthveni 



