Dicaelus (Paradicaelus) dilatatus Say 1823

Dicaelus dilatatus x sinuatus
Dicaelus dejeani Dejean and Boisduval, 1830:206, t. 100, f. 3; [type specimen in Oberthiir Coll. (fide Lindroth)]. Type locality: " Amerique septentrionale". Dejean, 1831:687. Le Conte, 1848:426; ["habitat in pro-
vinciis australibus"]. Dicaelus planicollis Le Conte, 1848:427. New synonymy; [type specimen a
female, in Le Conte Coll., MCZ no. 5709.]. Type locality: " in Georgia ad
montes " ; (determined from original description). Dicaelus carolinensis Casey, 1913:150; New synonymy; [type specimen a
male, in Casey Coll., USNM no. 47357]. Type locality: Southern Pines,
North Carolina; (determined from original description). Dicaelus dilatatus Brimley (not Say), 1938: 150. Loding, 1945: 18.
Typical members of this subspecies (as defined in the preceding section) exhibit the following combination of characters: males, length
21.3 mm. or less, ratio PN : W/W base 1.04 or less; females, length
21.4 mm. or less, and the same value given for the males with respect to the pronotal ratio; pronotum and dorsal surface of head almost smooth to rugulose, frontal impressions relatively broad and shallow, posterior transverse impression of moderate depth. For more detailed information on classifying individual specimens see the preceding section dealing with geographical variation. As a general rule, specimens collected in the area including the New England States eastward to about 77° W. longitude and southward to southern Virginia may be regarded as members of this subspecies.
Variation. — A summary of data on variation in total length is presented in table 30 and of values for the ratio PN : W/W base in table 29 (Mass.-Va. sample). Width in a composite sample of D. d. dilatatus varies as follows: 20 males, 8.6-10.3 mm. (9.2 mm.) ; 20 females, 9.0-10.6 mm. (9.8 mm.). The lines of macrosculpture on the dorsal surface of the head and pronotum vary from deeper to shallower, these surfaces appearing more or less rugulose. The length of the groove on the dorsal inner edge of the left mandible varies from considerably less than one half the length of the distance from apex of labrum to apex of mandible, to considerably more than half this distance. There is slight variation in the shape of the pronotum, as follows : sides more constricted anteriorly with lateral margins less arcuate ; more arcuate anteriorly; lateral margins posteriorly almost parallel. The lateral margins of the pronotum are beaded in all specimens of a composite sample of 40. Number of setae near the apical margin of the 6th abdominal sternite varies as follows: 20 males, 2-5 (3.4) ; 20 females, 6-10 (7.4). Variation in the shape of the median lobe of the male genitalia is slight.
Synonymical Notes. — Reasons for the synonymy presented above have been given in the section dealing with geographical variation. The result is that the portion of the range of Dicaelus dilatatus, which is regarded as the intergrade zone between two subspecific components, includes the type localities of three named forms. Workers wishing to have a name for this segment may use Dicaelus d. dejeani, and those who do not accept my proposal of a new name for the W. Pa. -la. sample may expand the definition of Dejean's name to include the latter.
Type locality. — Say did not indicate a type locality in his description of this species. However, in the original description, a reference to Carabus dilatatus Melsh. [nomen nudum] is made, so possibly the type specimen was taken in eastern Pennsylvania. Pennsylvania is given as the state in which this species occurs, by Say (1825), and the figure on plate 24 of that volume represents a typical member of the northeastern population of Dicaelus dilatatus. Therefore, I consider the type locality to be eastern Pennsylvania.
Notes on Immature Stages. — Schaupp (1878) described the larva of Dicaelus dilatatus and figured it ( 1879 : 21 ).
Distribution. — See the summary in conjunction with the diagnosis of this subspecies. I have collected specimens of Dicaelus d. dilatatus in the vicinity of Ithaca, New York, under cover in open fields and along stream margins. In the vicinity of Tuscaloosa, Alabama I have taken specimens classified here as intergrades, under wood chips and wet cardboard along the margin of a mixed deciduous wooded area, and under cover in open, river-bottom woodland.
Sixty-five males and fifty-one females collected in the following localities have been examined.
Connecticut: Fairfield County; Stamford. Litchfield County; Cornwall. District of Columbia: Woodridge. Maryland: Calvert County; Chesapeake Bch. Cecil County; Porter's Bridge. County not determined; Plummer Island, Wolfville. New Hampshire: County not determined; Cornish. New Jersey:
"New Jersey". "N.J." Bergen County; Ramsey. Middlesex County; N. Brunswick. Passaic County; Oak Ridge, Paterson. Sussex County; Hopatcong. Warren County; Phillipsburg. County not determined; Greenwood L. New York : Kings County ; Brooklyn. Orange County ; Ft. Montgomery, Greenwood Lake. " Seneca County ". " Tompkins County " ; Ithaca. Ulster County; Big Indian Valley. Westchester County; Peekskill. Massachusetts " Mass." Essex County ; Manchester. Hampden County ; Chicopee. Hampshire County; Mt. Tom. Norfolk County; Cohasset. "Norwich County." Suffolk County; Cambridge. Pennsylvania: "Pa." " Penn." Berks County; Reading, Shingleton. Centre County; State College. Cumberland County; Camphill, Enola, Le Moyne, N. Cumberland. Dauphin County; Harrisburg. Lebanon County; Campbell. Monroe County; Del. Water Gap. Northampton County; Easton, Wind Gap. Schuylkill County; Schuylkill. Sullivan County; Lopez. Wayne County ; Honesdale. County not determined ; Inglenook, Rockville. Virginia: Rockbridge County; Natural Bridge. Warwick County; Newport News. County not determined ; " Alex ", Buffalo Ck, Great Falls, Skyland. West Virginia: Greenbriar County; White Sulphur Springs.
Thirty-five males, and fifty-two females, classified here as intergrades between d. dilatatus and d. sinuatus, have been examined.
Alabama : Bibb County ; The Sinks. Chambers County ; Langdale. Clarke County ; Salt Mtn. Fayette County ; Fayette. Jackson County ; Point Rock. Madison County; Monte Sano. Mobile County; Mt. Vernon. Randolph County; Wadley. Talladega County; Talladega. Tuscaloosa County; Fleetwood, Talladega St. Forest, Tuscaloosa. County not determined ; Allstone, Tumblin Gap. Florida: Alachua County; Gainesville. Liberty County; Camp Torreya. Georgia: "Geo". Fulton County; Atlanta. Limpkin County; Dahlonega. Rabun County; Rabun Gap. Mississippi: George County; Lucedale. Perry County ; Richton. County not determined ; Moon. North Carolina : " N. Car." " N.C." Buncombe County ; Asheville. Moore County ; Southern Pines. Onslow County; New River. Orange County; Chapel Hill. Randolph County; Julian. South Carolina: " S.C." Oconee County; Clemson. Richland County; Columbia.

Dicaelus (Paradicaelus) dilatatus Say
The distinguishing characteristics of this species are in the keys.
This species ranges on the piedmont and coastal plain of eastern United States from central Massachusetts southward to northern Florida, and westward around the Appalachians on the Gulf Coast in the south, and through Ohio, Indiana and Illinois in the north, into the Mississippi Basin. The western limit is probably the 100th Meridian.
Several named forms, described originally as distinct species key out here, may be distinguished from one another as follows : D. dilatatus Say (type locality: restricted here to eastern Pennsylvania), size smaller (average length about 20-21 mm.), frontal impressions shallow, head and pronotum relatively smooth and shining, surface not coarsely rugose, sides of pronotum not sinuate and constricted posteriorly, (fig. 96a), nor broadly rounded, posterior transverse impression shallow; D. carolinensis Casey (type locality: Southern Pines, N. C. ) and D. planicollis Le Conte (type locality: Georgia), size larger (average length about 22-23 mm.), frontal impressions moderately deep, head and pronotum decidedly rugose, sides of pronotum not constricted and sinuate posteriorly, posterior transverse impression shallow ; the feature distinguishing these two is that the sides of the pronotum are more broadly rounded in carolinensis (fig. 96c) than in planicollis (fig. 96b) ; D. dejeani Dejean (type locality: restricted here to the coastal plain of Georgia), size larger than planicollis, (length usually 24-25 mm. ) , frontal impressions deep, dorsal surface of head and pronotum coarsely rugose, as in planicollis, sides of pronotum posteriorly constricted and sinuate or not (usually not constricted), posterior transverse impression deep. An additional form, similar to dejeani but differing in distribution (western Pennsylvania to southern Iowa) usually having the sides of the pronotum constricted, can be distinguished. The name dejeani has been applied to this group of specimens, but probably not correctly so.
The distinguishing characteristics of these forms seem to vary geographically, and these " species." are simply names applied to a continuum of variation.
To obtain samples of a statistically useful size it was necessary to group together specimens from a number of localities. The groupings have been made on two assumptions : first, that the species can be divided into at least two geographical races; second, that the characters involved, especially size, vary clinally. The most distinctive groups of specimens are those from northeastern United States east of the Appalachians, westward to Harrisburg, Pennsylvania, and north of North Carolina ; contrasted with specimens from localities in eastern United States, but west of the Appalachians, extending eastward to Pittsburgh, Pennsylvania, and north of the Gulf states. The remaining specimens, i.e. those from the Carolinas and Gulf states, were placed in two groups : a more northern one, including specimens from North Carolina (piedmont to coastal plain), South Carolina, and Georgia, and a second group including specimens from northern Florida (as far south as Gainesville), Alabama, and Mississippi (localities above and below Fall Line). The samples are discussed in sequence beginning with the northeasternmost (Mass.-Va. ), proceeding southward on the east coast (N. C.-Ga. ), westward on the Gulf Coast (Fla.-Miss. ), and ending with the western Pennsylvania-Iowa sample (W. Pa.-Ia. ). The characters to be discussed are those which vary geographically, or which have been used to distinguish the named forms included in this species.
The macrosculpture of the dorsal surface of the head and pronotum is usually less pronounced in the smaller, northeastern specimens than in the larger western and southeastern individuals. The macrosculpture of my series of Virginia and New Jersey specimens is slightly more pronounced on the average, and more specimens from North Carolina and southward have the integument coarsely rugose. The average maximum condition is reached in specimens from South Carolina and southward, westward, and northward, to the west of the Appalachians.
The depth of the frontal impressions of the head varies from shallow to deep following about the same pattern as the macrosculpture — the specimens from the northeast exhibiting the shallower impressions, becoming progressively deeper and more linear southward, the specimens included in the Fla.-Miss. and W. Pa.-Ia. samples with the deepest impressions. The posterior transverse impression is moderately deep in specimens of the Mass.-Va. sample, varying from shallow to deep in specimens of the remaining samples ; shallow being prevalent in the N. C.-Ga. sample, deep being universal in the W. Pa.-Ia. sample
but occurring frequently in the Fla.-Miss. sample, along with the shallow and moderately deep conditions.
The sides of the pronotum posteriorly of all the specimens of the W. Pa. -la. sample are moderate to strongly sinuate. The sides of the pronotum appear to converge more strongly anteriorly in some specimens of the N. C.-Ga. and Fla.-Miss. samples than is usual for the Mass.-Va. sample. The disc of the pronotum appears to be more convex in specimens of the Mass.-Va. and W. Pa.-Ia. samples, flatter in some specimens of the N. C.-Ga. and Fla.-Miss. samples. A combination of configuration of the sides of the pronotum with convexity of the disc and depth of the posterior transverse impression, gives several different pronotal types which distinguish the named forms included in this species.
Actually, the three most distinctive types are dilatatus, carolinensis and sinuate (W. Pa.-Ia. sample). The planicollis pronotum bridges the gap between carolinensis and dilatatus, and the dejeani type bridges the gap between dilatatus and sinuate. All specimens of the Mass.-Va. sample have the dilatatus type of pronotum, and all specimens of the W. Pa.-Ia. sample have the sinuate type of pronotum. Specimens comprising the other two samples exhibit all types and intergrades between them. Table 28 contains a summary, by states, of the frequency distribution of the dilatatus, carolinensis, and sinuate types. The intermediate category includes specimens which have the dejeani or planicollis type.
These data show that the carolinensis type of pronotum is relatively rare and that its distribution is spotty. Specimens are known from : Southern Pines ( 7 out of 9, the other two •intermediate between carolinensis and dilatatus) ; Columbia, South Carolina (taken with a planicollis-ty-pe specimen) ; Rock Bluff, Florida (coastal plain) ; Wadley, Bibb County (1 specimen, and four with a dejeani-type pronotum), and Langdale, Alabama. I contend that carolinensis is simply an extreme variant, genetic or otherwise, and should not be recognized taxonomically. In the following analysis of size and pronotal variation specimens having the carol inensis-type pronotum are included with the other specimens comprising the N. C.-Ga. and Fla.-Miss. samples.
The proportions of the pronotum vary geographically, with specimens of the W. Pa.-Ia. sample usually having a narrower pronotal base than specimens comprising the other samples. The single ratio that best shows this is the width at widest point divided by width at base. Values for this ratio were obtained and are presented in table 29.
Size, as expressed by total length, also seems to vary geographically from the northeast southward to the Gulf states, with smaller specimens in the northeast and larger specimens southward (table 30).
Statistical analysis of the data for size and pronotal variation showed that the differences between the Mass.-Va. and W. Pa.-Ia. were of subspecific value (see Ball: 1954, tables 40-43), and a hybrid index was worked out utilizing the same method as outlined for Dicaelus funnis. A summary of the basis for assignment of hybrid index values is presented in table 31, and a frequency distribution of the values themselves is presented in table 32.
The suggested type locality for typical dilatatus falls within the area included in the Mass.-Va. sample; the type localities of carolinensis, planicollis, and dcjeani fall within the areas represented by the N. C.-Ga. and Fla.-Miss. samples, the intergrades, and the W. Pa.-Ia. sample has not been named. As none of the names available really apply to the latter sample, I propose to call it Dicaelus dilatatus sinuatus. The northeastern population, represented by the Mass.-Va. sample, is the typical subspecies. The remaining names, since they apply to intergrading populations between the two extremes, may be profitably abandoned.
I suggest that population samples may be most effectively identified by determining the distribution of their hybrid index values. In the case of individual specimens, they may be named either on the basis of where they were collected or their hybrid index values : 2-3, d. dilatatus; 5-6, d. sinuatus; 4, intergrade.
A striking fact regarding the geographical distribution of the two races of this species is that in the southeast they are connected by a zone of intergradation probably some 600 miles in extent (approximate linear distance from Durham, North Carolina to Mobile, Alabama). In the state of Pennsylvania, typical specimens of sinuatus occur at Pittsburgh, and typical specimens of dilatatus at Harrisburg, localities which are about 150 miles apart. The zone of intergradation is either much narrower here than farther south, or the species does not occur in the intervening areas in Pennsylvania, due perhaps to ecologic fac
tors, or time, or because the end points of the cline are specifically distinct.

Dicaelus dilatatus is a species of ground beetle in the family Carabidae. It is found in North America.