THE IMMATURE STAGES OF THE HARLEQUIN BUG, DZNDYMUS

Transcription

1 J. Aust. eiit. So t : THE IMMATURE STAGES OF THE HARLEQUIN BUG, DZNDYMUS VERSICOLOR (HERRICH-SCHAEFFER)(HEMIPTERA: PYRRHOCORIDAE) P. P. STAHLE Department of Zoology, La Trobe University, Bundoora, Vic Abstract The immature stages of Dindymus versicolor are illustrated and described. Introduction In his review of the taxonomic significance of the characters of immature insects, van Emden (1957) stressed the importance of describing the immature forms and how little of this work had been done. Richter (1972), in his appraisal of entomological studies at major research centres and museums of the world, concluded there was still a paucity of information on the morphology and biology of immature insects. Dindymus versicolor (Herrich-Schaeffer) is a minor pest of soft fruit orchards, market gardens and home gardens in southeastern Australia and Tasmania (French 1891; French 1933; McKeown 1942; Evans 1943), but the nymphs have not been described even though they contribute directly to the pest status of this species. Further, Dindymus versicolor, as the major representative of the family Pyrrhocoridae in southeastern Australia (Tillyard 1926), has been neglected compared to the family s northern Australian representative, Dysdercus sidae Montrouzier, once considered to pose a serious threat to the cotton industry (Froggatt 1923; Gurney 1924; Ballard and Evans 1928). The immature stages of Dysdercus sidue were described by Ballard and Evans (1928). The description of the five instars of Dindymus versicolor below should be of value in the recognition of pests of soft fruit in Australia. FIG. l-dindymus versicolor, first instar, dorsal view.

2 272 P. P. STAHLE TABLE DINDYMUS VERSICOLOR: MEASUREMENTS OF NYMPHS (MEAN AND STANDARD ERROR IN PARENTHESES, ALL MEASUREMENTS IN mm) Body length Body width Head length Interocular distance Head width Pronotum length Pronotum width Instar I Instar I1 Instar 111 Instar IV Instar V (1.91 f 0.01) (3.14 f 0.08) (5.00 f 0.07) (7.34 f 0.09) (8.73 f 0.17) (0.98 f 0.01) (1.35 f 0.04) (2.24 f 0.06) (3.38 f 0.07) (3.59 f 0.08) (0.43 f 0.01) (0.79 f 0.02) (1.14 f 0.02) (1.51 f 0.02) (2.00 f 0.03) (0.41 f 0.003) (0.58 f 0.005) (0.68 f 0.01) (0.86 f 0.01) (1.07 f 0.01) (0.58 f 0.003) (0.84 f 0.01) (1.08 f 0.01) (1.41 f 0.01) ( ) (0.18 f 0.004) (0.36 f 0.01) (0.52 f 0.01) (0.81 f 0.01) (1.14 f 0.03) (0.75 f 0.01) (0.93 f 0.01) (1.20 f 0.02) (1.72 f 0.02) (2.56 f 0.05) Rostrum (0.23 f 0.003) (0.48 f 0.01) (0.70 f 0.01) (0.99 f 0.01) (0.22 f 0.003) (0.47 f 0.01) (0.70 f 0.01) (0.98 f 0.01) (0.21 f 0.004) (0.39 f 0.005) (0.55 f 0.005) (0.80 f 0.01) (0.22 f 0.004) (0.42 f 0.003) (0.55 f 0.005) (0.71 f 0.01) Antennae ( ) (1.24 f 0.01) (1.06 f 0.02) (0.90 f 0.01) (0.23 f 0.004) (0.58 f 0.01) (0.82 f 0.01) (1.23 f 0.01) (1.73 f 0.02) (0.21 f 0.004) (0.50 f 0.01) (0.73 f 0.01) (1.06 f 0.01) (1.46 f 0.02) (0.20 f 0.003) (0.43 f 0.01) (0.62 f 0.01) (0.87 f 0.01) (1.16 f 0.02) (0.51 f 0.003) (0.79 f 0.01) (1.05 f 0.01) (1.42 k 0.02) (1.81 f 0.02) Fore leg Femur Tibia Tarsus Mid leg Femur Tibia Tarsus (0.39 f 0.005) (0.78 f 0.01) (1.16 f 0.01) (1.72 f o.oi) (2.61 f 0.03) (0.43 f 0.005) (0.82 f 0.01) (1.20 f 0.02) (1.78 f 0.02) (2.53 f 0.03) (0.34 f 0.01) (0.46 f 0.01) (0.55 f 0.01) (0.83 f 0.01) (1.18 f 0.02) (0.41 f 0.005) (0.83 f 0.01) (1.27 f 0.02) (1.89 f 0.02) (2.86 f 0.04) (0.42 f 0.004) (0.87 f 0.01) (1.30 f 0.02) (1.92 f 0.02) (2.77 f 0.04) (0.34 f 0.004) (0.51 f 0.004) (0.62 f 0.01) (0.88 f 0.01) (1.22 f 0.02) Hind leg Femur (0.46 f 0.01) (1.04 f 0.01) (1.61 f 0.02) (2.60 f 0.04) (3.66 f 0.04) Tibia (0.51 f 0.01) (1.20 f 0.01) (1.80 f 0.02) (2.82 f 0.03) (4.00 f 0.64) Tarsus (0.40 f 0.01) (0.63 f 0.01) (0.79 f 0.02) (1.25 f 0.02) (1.52 f 0.03) Methods Measurements were made from fifteen individuals of each instar, collected from the La Trobe University campus, and preserved in 70% ethanol. To facilitate measurement, the appendages were severed from the body and held flat between two glass slides. The 25 eggs measured were collected from a captive colony kept in a field ca e All measurements are in millimetres (Table). Descriptions and drawings were made from freshly killef specimens. The following dimensions were measured: body length (from tip of tylus to end of abdomen); body width (maximum, normally abdominal segment IV or V); head len th (length of head capsule, along midline from tip of tylus to posterior edge of vertex); interocular chance (shortest distance between

3 HARLEQUIN BUG IMMATURES 273 FIG 2- Dindymus versicolor, second instar, dorsal view. FIG. 3- Dindymus versicolor, third instar, dorsal view.

4 214 P. P. STAHLE FIG. 4- Dindymus versicolor, fourth instar, dorsal view. FIG. 5-Dindymus versicolor, fifth instar, dorsal view.

5 HARLEQUIN BUG IMMATURES 275 margins of orbits as seen from above); head width (maximum including eyes, as seen from above); pronotum length (along midline); pronotum width (maximum); lengths of rostral se ents(maximum len ths ents I, 2, 3 and 4); lengths of antenna1 segments (maximum lengths ogegments 1, 2, 3 ancf4); P,',zrof leg segments (maximum lengths of femur, tibia and tarsus excluding claws). Descriptions of immature stages Egg Length 1.33 f 0.01, width 0.87 f 0.01 ; ovoid; chorion opalescent, with regular hexagonal reticulations; four, five or six evenly spaced micropylar chorionic processes each ca 0.02 long on cephalic pole. No true operculum (chorion splitting irregularly at eclosion). First instur (Fig. 1) Heudpale orange, not deflexed; eyes scarlet; anterolateral margin sli htly sinuate with tylus extending distinctly beyond juga; rostrum transparent, stylets visible along full lengtf ; rostrum extending to posterior edge of abdominal sternum 111. Antennae colourless, transparent, four-segmented; segments fusiform; ratio of segment lengths 1.55 : 1.05: 1 : 2.55 ; segments I and 2 sparsely setose, 3 and 4 setose. Thorax pale orange, translucent; lateral margins carinate; longitudinal ecdysial suture extending along midline from anterior margin of pronotum to posterior margin of metanotum; anterior margin of pronotum very slightly concave. Abdomen pale orange, translucent; small dorsal medial sutural ostioles between segments 111 and IV, IV and V, V and VI (positioned as in all pyrrhocorid nymphs and as shown in Figs); sternum 111 with a pair of minute trichobothria on either side of midline; sternum IV with two triplets of minute trichobothria just posterolateral to pairs on segment 111; trichobothria of segments V, VI and VII adjacent to spiracles; segment IV widest. Legs colourless, trans arent; partial rosette of fuscescent s ines on ventral side of distal end of fore, mid and hind tibiae; tarsarclaws brown ; tibiae and tarsi slightc setose. Second instar (Fig. 2) Head as in first instar but colour fuscorufous, gula scarlet in midline; eyes fuscescent red. Antennae as in first instar but ratio of segment lengths 1.35: 1.17: 1 : 1.84: proximal end of segment 4 cream; slight lateral flexure of segment I. Thorax sclerotised regions fuscorufous; longitudinal ecdysial suture extending to osterior margin of metanotum; lateral edges of pleura unsclerotised; rostral canal red on prosternum, wkte on mesosternum and metasternum. Abdomen orange; one central fuscorufous spot on sternum of segment VIII continuous with totally fuscorufous segment IX; minute fuscorufous patches in midline on anterior edges of sterna V, VI and VII; two fuscorufous spots adjacent to hind coxae on sternum 11. An almost circular fuscorufous peritreme surrounding each dorsal ostiole, peritremes intersegmental ; two very small fuscorufous patches on suture between terga I and 11, about halfway between midline and lateral edge; pigment of spiracles very slightly darker than surrounds. Legs as in first instar but fuscorufous, with two small teeth on distal end of anterolateral surface of fore femora; all tibiae and tarsi with prominent s ines on ventral surface; femora with sparse, barely discernible setae and scarlet ligulate band on dorsafsurface proximally, running longitudinally for about onequarter length of segment. Third instar (Fig. 3) Head as in second instar but colour darker. Antennae as in second instar; ratio ofsegment lengths 1.32: 1.18: 1 : Thorax as in second instar but darker; pleura almost totally sclerotised with sclerotised region of propleura and mesopleura continuous with sclerotised region of pronotum and mesonotum respectively; wing buds just discenible as small bulges on mesonotum and metanotum. Abdomen as in second instar but fuscorufous patches larger. Legs as in second instar but longer. Fourth insrur (Fig. 4) Head as in third instar but colour darker. Antennae as in third instar but darker; ratio of segment lengths 1.41 : 1.22: 1 : Thorax as in third instar but darker and wing buds evident as posteriorly directed projections.

6 276 P. P. STAHLE Abdomen as in third instar but fuscorufous patches of peritremes and on venter larger; poorly delimited fuscorufous patches on either side of peritreme on terga of segments IV, V and V1 and one anterior to peritreme of segments 111 and IV; spiracles darkly pigmented. Legs as in third instar but longer. Fifth instar (Fig. 5) Shape and intensity of patches of colour varying considerably. Head as in fourth instar but black. Antennae as in fourth instar but black; ratio of segment lengths 1.49: 1.26: Thorax. - Prothorax scarlet ; flanges of episternum and epimeron white ; margin and collar of pronotum sometimes yellow. Mesothorax black; patches of scarlet on pleura; flanges of episternum and epimeron white; fore win bud black and extending to middle of abdominal tergum 111. Metathorax: Sternum black with white patcfes on pleura; flan e ofepisternum white; hind wing buds completely covered by fore wing buds, translucent fuscorufous, fa& towards centre of wing bud. Abdomen.-Dorsum: Segments 11,111 and 1V fuscorufous along midline fading to scarlet; segments V, VI, VII and VIII fuscorufous, fading to cream on lateral ed es and to white halo around fuscorufous patches of peritremes; otherwise as in fourth instar. Vente.r:%idline pi ent patches black and larger than in fourth instar; segment I1 scarlet; lateral edge of segments 111 an!& scarlet fading towards pale reen midline; lateral edges of se ents V, VI and VII fuscorufous fading towards ill-defined pale green and along midline; the green oregments 111, IV, V, VI and VII fading to white posteriorly on each segment; otherwise as in fourth instar. Legs as in fourth instar but tibiae more spinulate. Comments The immature stages of Dindymus versicolor key to Pyrrhocoridae using Leston and Scudder's (1956) key to British heteropteran families. The five nymphal instars may be distin ished from one another on colour pattern alone and by Southwood's (1956) key. T f? e development of Dindymus versicolor nymphs closely parallels that of other pyrrhocorids such as Dysdercus sp (Ballard and Evans 1928; Fuseini and Kumar 1975). In areas of Australia where hndymus versicolor and Dysdercus sidae are sympatric there may be some difficulty in se arating the first instars of the two species, although Dindymus versicolor is slightly f arger and does not exhibit a su r- numerary moult during the first stadium (Ballard and Evans 1928). The second, t K" ird and fourth instars of Dysdercus sidae may be distinguished from those of Dindymus versicolor by the presence of a pale longitudinal line bisecting the dorsum of the thorax. The fifth instar of Dysdercussidaemay be distinguished from that of Dindymus versicolor by the presence of a red spot above and below each eye. References BALLARD, E. and EVANS, M. G. (1928).-Dysdercus sidae, Montr., in Queensland. Bull. enr. Res. 18: VAN EMDEN, F. I. (1957).-The taxonomic significance of the characters of immature insects. A. Rev. Ent. 2: EVANS, J. W. (1943).-"Insect Pests and their Control". H. H. Pimblett; Government Printer: Hobart. FRENCH, C. (1891).-"AHandbook ofthe destructive Insects of Victoria Part 1". R. S. Brain, Government Printer: Melbourne. FRENCH, C. JNR (1933).-New records of plants attacked by native insects; the Harlequin Bug (Dindymus versicolor Schon.). Victorian Nut. 50: 47. FROGGATT, W. W. (1923).-Insect pests ofcultivated cotton plant. No. 3. Cotton stainers and other plant buns. Apric. Gaz. N.S. W. 34: FUWINI, B. A.-and"Kw, R. (1975).-Biology and immature stages of cotton stainers (Heteroptera: rrhocoridae) found in Ghana. Biol. J. Linn. Soc. 7: GURNEY, W%. (1924).-Insect pests of cotton in New South Wales. Agric. Gaz. N.S. W. F: LESTON, D. and SCUDDER, G. G. E. (1956).-A key to larvae of the families of Britlsh Hemiptera- Heteroptera. Entomologist 89: ~ MCKEOWN, K. C. (1942).--"Australian Insects: an introductory Handbook". Royal Zoological Society of New South Wales: Sydney. RICHTER, P. 0. (1972).-Taxonomy of immature insects-present status and future needs. Bull. ent. Soc. Am. 18: SOLITHWOOD, T. R. E. (1956).-A key to determine the instar of an heteropterous larva. Entomologist 89: TILLYARD, R. J. (1926). "The Insects of Australia and New Zealand". Angus and Robertson: Sydney. [Manuscript received 7 June