FIELD OBSERVATIONS OF TROPIDACRIS COLLARIS (ORTHOPTERA: ROMALEIDAE) Christopher K. Starr Dep't of Life Sciences, University of the West Indies,St Augustine, Trinidad & 'Ibbago cstarr{jj}centre.uwi.tt Tropidacris i s a neotropi c al genus of three known s peci es aggregation close to the ground on a small shrub c lose along­ that include the largest g r asshoppers in the world (Carbone ll side the gulch. I netted a sampl e of these, which disturbance 19 86). Two species, T. collaris and T. crisrata, have very caused the remai nin g individuals to scatter. Some time later broad ranges that include mos t of South America north of the I returned to that spot and found th e aggregation re-formed southern cone . The former is the species found on Margarita in a s imilar s ituation less than a meter from where I had first Is land, wh il e the range of the latter inc ludes Tri nidad and found it. Although I did not attempt to quantify ad ult densi­ Tobago. The two are readily distingui s hed by the fo llowing ty in any part of the gulch, they appeared to be most concen­ adult characters (Carbonell 1984.1986): a) a nte nnae enti rely trated within a very few meters of the aggregation of hoppers. yellow in T. collaris, basal two segments brown to black in T. I tas ted one hopper and found it to be very biller. approx­ cristata, b) dorsa l crest of pronotum continu ing o nto posteri­ imately like an adu lt mo narch butterfly (Danaus plexippus). ormas t lobe (metazona) in T . cristata but not T. collaris, c) Thi s distastefulness is consistent with the orange-and-black hindwings mainly orange to red in T. cristata, green Lo blue in body co lou rat ion . T. collaris. We will di s regard here the third, s maller s pecies, Casual observations els ewhe re around La Vecindad con­ T. de ca mps i, known from a si ng le locality in Colombia. firmed that th e adult grasshoppers were abundant over a Hoppers (larvae) of Tropidacris s how contrasting, evident­ large area. The local people with whom I spoke seemed ly warning colouration, whil e adults at res t are very well cam­ un surp ri sed by thi s and told me that it is a seasonal phenom­ ouflaged against vegetation . The forewing s bear a strong enon, although they were vague about the particular season resemblance to leaves, while the hindwings present s triking of appearance of adults or whether they are abundant every fla s h colouration. especially in T. cristata ( Rowell 1983 ; pers . year. They told me that T. collaris is locally known as lall­ obs.). gosta or fiangaragato. Adult Tropidacris are spectacular insects and are not rare Th e adults that I collected amounted to four fema les and throughout most of the genus's range . T. collaris is often 22 males with mean hind - femur le n g t hs of 38.8 mm ( range encountered a l ong much of the Caribbean coast and th e 36.5 - 42.0 mm) and 33.3 mm ( range 29 .0 - 37.5 mm ). respec­ ll anos region of Venezuela (F. Cerda, pers. co m m.). tively . Meas urement was of alcohol -preserved specimens with None thel ess, they are not often encountered in large num­ an ordi nary ruler to the nearest half millimeter. bers. I n Trinidad I have never seen two adult T. cristata in Di ssection of the females s howed that the two largest had one day and possibly not t wo in the same ca le ndar month. well-developed ovaries with apparently mature ova. The next Rowell 's (1983) brief account of T. cristata summarized the largest had slightl y developed ovaries. while the s mallest bi ological in for mation on record fo r the genus. ending wit h s howed n o ovarian development. t he remark that "Nothing very much is known of any of The sa mpl e of hoppers compri sed 19 fema les and 10 males . them." Carbonell ( 1986) s upplied s ome further details, not­ with hind-femur le ngths shown in Fig . I. Sex is readily deter­ ing that in both species the hoppers are g rega ri ous. genera­ mined by ventral examination of the abdo minal terminalia. tion s are not di screte, and all stages feed on a variety of Measurement was with an eyepiece micrometer to the nearest p l ants. He a lso noted that T. collaris s hows a very broad 0.16 mm; c ho ice of the left or righ t leg was according to con­ habitat range from humid forest to drier. more open forma­ ve nience . tions , wh il e T. c ristata is largel y abse nt from o pe n , dry for­ mations. It is this sparseness of biological information that justifies the present brief observations. All are fro m an area of cactus scrub outsid e the village of La Vecindad on the island of Margarita , Venez.uela, on 19 August 1997. Thi s was toward the end of a dry season th at lasts the greater part of the year I "6 on Margarita. Observation s were concentrated in a s hallow , .i \ dry gulch about 150 m long, lined with grasses, sedges, and z many herbaceou s broadleaf plant s but few trees. Hind-Femur Length (mm) M y attention was d raw n to T. collan's when I happened to see two adults in quick succession. I began a deliberate search and collected a ll adults that I could f ind . Figure 1: Frequency distribution of hind-femur length in 19 female and The on ly hoppers that I encountered were a s ing l e. dense 10 male hoppers of Tropidacris collaris from an aggregation. Tropidacris collaris 47 The size-freque ncy di stribution of hoppers indi cates that Thanks to C.S. Carbonell, F. Cerda and H.F. Rowe ll for crit­ these represent two ins ta rs, with males on average s li ghtl y ical comment on these observations. smaller th an same-i nstar females. Thi s conclu sion is corrob­ orated by consi sten t within-sex. differences in the form of the References abdominal terminalia bet ween th e two size-groups. The bas is of the strongly skewed sex-ratio in the sample of Carbone l l, C.S. 1984. Nomenclat ure and systematics of hoppers is not readily apparent. Given the sma ll data-set, I do Tropidacris a od EUlropidacris (O rthopte ra. Acridoidea. not discount the possibility that it is du e to sa mpling bias. Romaleidae). Norulae Naturae (Philadelphia) (461): I ­ Taken by themse lves , the observations of adults are cons is­ ll. tent with th e hypothesis of a hi g hly seasonal life cycle, with Carbonell, C.S. 1986. Revi sion of the neotropical genus males developing s omewhat faster than females and a con­ Tropidacris (Orthoptera. Acridoidea. Roma leidae. centration of breeding around the start of the rainy season. Romaleinae). Proc. Acad. lIat. Sci. Philadelphia 138:366- The presence of hoppers during the same time suggests that 402. T. collQr/'s breeds at two dist inct seasons on Ma rgarita. Rowe ll , H . F . 1983. Tropidacris crisrata (saltamonte 0 cha­ I regret that I was unable to extend these few opportunistic pulfn gigante. giant red-winged grasshopper). In D.H. observations and hope that they may stimulate someone else Janzen (ed.), Costa Rican Natural History. Univ. Chicago to undertake a more thorough s tudy. Press. Chi cago Pp. 772-773 .