20 
Psyche 
[March 
seum (Nat. Hist.), University of Connecticut, J. A. Slater, P. D. 
Ashlock, and author’s collections. 
From the other species of Ligyrocoris sensu stricto, L. caricis is 
readily distinguished by its relatively small size and narrow form. 
Like diffusus, caricis has an incomplete fuscous fascia on the hemelytra, 
smaller size, and the hind basal metatarsal segment only twice the 
length of the distal two combined. However, caricis appears to be 
more closely related to the larger species depictus and sylvestris for it 
shares with them a relatively narrow pronotum with very few erect 
setae, fore femora with short setae or none, a labium which only 
attains the mesocoxae, relatively long antennae, a similar pattern of 
spines on the aedeagal conjunctiva, and a brachypterous condition. 
L. slossoni Barb, differs in having a labium which attains the third 
abdominal segment and a complete fascia on the 1 hemelytra. 
It should be noted here that the fascia which Barber (1921) used 
as a major character to separate species is quite variable, and specimens 
of depictus will go to both sides of Barber’s key on this character. 
Actually depictus is very closely related to L. sylvestris rather than 
to the very different L. litigiosus Barb, and other species which lack 
the fascia. 
As all the species mentioned above are closely related, it is fortunate 
that the species concepts could be verified by mating experiments. In 
all four species, caricis, diffusus, sylvestris, and depictus, the males 
display a courtship “dance.” When a female was approached by a 
male of a different species, she became extremely excited, and actively 
avoided the strange male so that cross-mating does not occur. This 
behavior is entirely different from the normal “reluctant response” 
of a female to a male of the same species. These behavior patterns will 
be discussed in detail in a later contribution. 
Key to the Species of Ligyrocoris of the Northeastern United States 
1. Pronotum with many (ca. 25 or more) erect setae (Fig. 1) ; fore 
femora with outer row of setae present and longer than basal 
width of fore tibiae (Fig. 2) ; labium reaching between hind 
coaxe; labial segments II and III subequal (.701.67 mm.) ; nearly 
always macropterous with membrane of hemelytra reaching beyond 
ter gum 7 diffusus (Uhler) 
Pronotum with few (ca. 10) erect setae (Fig. 3); fore femora 
without an outer row of short setae, if present (Fig. 4), length 
always less than basal width of fore tibiae ; labium not reaching 
between metacoxae, usually just attaining mesocoxae; labial seg- 
ment III shorter than II, often subequal to I (at most, II .81 
mm., Ill .70 mm.) ; always brachypterous, membrane of hemely- 
tra rarely reaching beyond ter gum 7 2 
