THE WASM ANN JO U RN A L OF BIOLO GY VoL. 12, No. 2 S U~!l\U; R, 1954 The Biology of Zonitis atripennis flavida LeConte (Coleoptera: Meloidae)' RICHARD B. SELANDER,' Depm·tntent of Entomol­ ogy, Uni ve1·sity of Illinois, and GEORGE E . BOHART, U.S.D.A., A g1·ic1tltural Resea1·ch Administration, B1t­ rea1t ot Entomology and Plant Q1w1·antine Inasmuch as practically no biolog·ical data on the New World blister beetles of t he genus Zonitis Fabricius have been published, it seems appropriate to present the following info rmation con­ cerning one of the common North American species, Z. at1·ipennis (Say) . Previously our knowledge of the biology of the genus has been based on accounts of two Old \Vorld species, Z . pmeusta Fab­ ricius and Z. imnwcula.ta (Olivier ). Among the works dealing with one or both of these species are those of Rossi ( 1792-94), Fabre (1857, 1882, 1886), Giraud (1866 ), Beauregard (1890), Vachal ( 1892), and Cros ( 1921, 1928) . Most of these works pre­ sent descriptions of two or three of the larval instars or their exuviae found in the cells of various bees (see table 1). Apparently none of the authors who have dealt with the development of Zonitis larvae have noticed the complement of larval instars. According to the accounts of Fabre and Beauregard, the imma­ ture stages include a "primary larva," which attaches to the host bee and is carried to the nest, a "secondary larva," which feeds on the provisioned material in the bee cell or cells, a " pseudo­ chrysalid" resting stage, a "third larva," and a pupa. However, in discussing Z. immaculata, Cros (1928) indicated that the "secondary larva" actually includes the second, third, Received for publication November 24, 1952 . 1. Acknowledgments are made to W. P. N ye, who, in association with the junior author, prepared the photog raphs il lustrating this paper, and to C. D . Michener, wh o kindly checked over and brought up to date the generic assignments of the species of bees listed in table 1. 2. A National Science Foundation fellowship partially supported the senior author's par- ticipation in this study ; the University of Utah and the I ll inois Natural History Sur vey sup­ plied facilities for work. [ 227] 228 THE W ASMANN JOURNAL OF BIOLOGY, Vor.. 12, 1954 and fourth larval instars. Furthermore, it now appears that the "third larva" in these species consists of more than a single instar. DIS'l'RIBU'l'IOK OF ZON I'l'IS A'l'RIPENNIS Zonitis at-ripennis is widely distributed in the western United States. It is represented by two subspecies, which were univer­ sally treated in the literature as separate species prior to the TABLJ<: 1 Lm·val hosts of some speci es ot Zonitis Zonitis -~1Jecies Author··ity Z. ctt1"i1J ennis f/a.v ida LeConte Nornia m.. rnelander·i Cockerell.. .......................... New r ecord Z. immaculata (Olivier) Anthidiurn rnanicatum (Linnaeus) ( n ............ .. Cros, 1928 Anthocopa longispina (Perez) .... .. Cros, 1928 H oplitis (1) cavigena ( P e•·ez) ..... .. ... Cros, 1928 Hoplitis nwr-awitzi (Gers taecker ) .. Cros, 1928 Hoplitis l1"iclentata (Dufour and P erris) ...... Giraud, 1866; Fabre, 1882 I cter·anthidi1tm ( t ) bellicos1tm (Lepeletier ) .... .. Fabre, 1886; Beauregard, 1890 I ct er-anthiclium discoidale (Latreille) ( f) ........ Cros, 1928 Megachile (Chctli codoma) rmtr·ar-ia (Retzius) .... .. Rossi, 1792-94 Osrnia 1)S e1tdoauntlenta Dours .. .......... .. Cros, 1928 Osmia sp. (0. latr·eill ei (Spinola) or 0. tr·icor·nis Latreille ) Fabre, 1882 Osrnia spp . ....... .. Cros, 1928 Z. 7J r-aeusta Fabricius A nthidimn sp. .. ... ................ ................. Cros, 1928 Anthocopa longispina. (Perez) .. Cros, 1928 AnthoC01Ja, saunder·si (Va cha !) .. Vacha!, 1892; Cros, 1928 l cter·anthidium 0 ) bellicos·urn ( Lepeletier ) ........ F a bre, 1886 Megachile se1'iccms Fonscolombe........ Fabre, 1886; Vacha!, 1892 111egachile sp. .......................... .. ................ .... Cros, 1928 Osn·tia 1J seudoaw·ulenta Dours....... Cros, 1928 Osrnia sp. .................... Cros, 1928 Pa.nmthidielhtrn lit1tr-at1trn sca1mlar-e (Latreille) Fabre, 1886 Z. sp. Co llet es daviesamus var. signat1tS Verhoeff.. ........ Beauregard. 1890 Figure 1. Nornia rn. rnela.nde·l"i Cockerell. N esting s ite, showing wind­ blown chimneys, salt c rust of undisturbed s urface, and t ypical vegeta· tion. Figure 2. Nomia m. m elancler··i Cockerell. Adult female. BIOLOGY OF ZONITIS-SELANDER Al'W BOHART 229 2 230 THE WASMANN JOURNAL OF BIOLOGY, Vor.. 12, 1954 appearance of a recent paper by McSwain (1951 ). According to available records, the range of the subspecies Zonitis atripennis fiavida LeConte extends from the Pacific Coast eastward to cen­ tral Colorado and New Mexico, where it meets that of the nomi­ nate subspecies, which ranges still farther eastward, onto the Great Plains. The eastern limits of the species are unknown to us, but we have one record as far east as \Vest Virginia. 'rhe western subspecies, Z . a. fia vida, is relatively common throughout Utah, where the present studies were undertaken. In the desert areas near Delta and Fillmore, Millard County, it has been frequently encountered as a parasite in the nests of the halictid bee Nomia melande1·i rnelanderi Cockerell. The following account of the biology of this bee may be helpful in explaining the details of this parasitism. BIOLOGY OF N OMIA l\1 . MELANDER! This bee (fi gure 2) nests gregariously, often in great concen­ tration, in alkaline desert regions, selecting areas where the sub­ surface soil remains soft and moist throughout the summer months. Typically, a single nest consists of a burrow about one foot in depth, which is irregularly branched to form small aggre­ gates of cells (fi gure 3). The total number of cells per burrow varies from twelve to twenty. The female bee hardens the wall of the main burrow by tamping with her abdomen. The walls of the cells are carefully shaped and smoothed and then polished by t he addition of a secretion produced by the female bee. When the nest is first excavated, the entrance is surrounded by a low mound of soil , but within a few days the excavated soil is generally scattered by the wind so that the hardened wall of the burrow forms a short chimney at the surface (fi gure 1). Each cell is provisioned with a soft ball of honey and pollen, upon which a single elongate egg is deposited before the cell entrance is sealed. According to observations of nests in Washington, southern Idaho, and Cache Valley, in northern Utah, N. m. rn elanderi has but one generation a year. In these areas, as in the more southern Millard County, Utah, adults begin emerging in early July, and fema les may be found provisioning their nests throughout that month and during most of August. During late August and early Septe mh er the larvae complete their feeding and reach the over- BIOLOGY OF ZONITIS-SELANDER AND BOHART 231 wintering prepupal stage. In the Millard County area, however, it appears that part of the larvae produced by overwintering bees complete their development during the same summer and emerge during the last half of August, thus forming a small second gener­ ation. Th e progeny of this late emerging generation overwinter in the usual manner, as prepupae. Since only a small proportion of the larvae produced by the first generation complete their develop­ ment in this manner, it appears that, at least in the Millard County area, the second generation adults develop from those larvae produced by the earliest emerging adults of the first gen­ eration or possibly from those larvae which occupy cells relatively near the surface of the soil. Farther to the south, where the first emergence of adults is much earlier, two generations a year of N. m. melande1·i may be the rule rath~r than the exception. The developmental stages of this bee are shown in figures 4 and 7 (see also Bohart, 1947) . In Utah Nomia m. melande·ri is an important pollinator of al­ falfa. Other introduced plants which are visited include yellow and white sweetclover, Russian-thistle (Salsola kali var. tenui­ folia Tausch), bindweed (Convolvulus m·vensis Linnaeus), alfalfa dodders ( Cuscuta spp.), and tamarisk ( Tamarix gallica Lin­ naeus). Alfalfa, white sweetclover, and Russian-thistle provide all but a small percentage of the pollen gathered in the cultivated areas. Late in the season, when these sources become scarce, rabbitbrush ( Ch1·ysothamnus nauseosus (Pallas)), hawksbeard ( C·repis g7-<tnca (Nuttall )), marsh dodder ( Cnscnta salina Engel­ mann), and teasel (Dipsa.cus sp.) are used, generally to supple­ ment small loads of pollen gleaned from the declining major sources. The bee plants ( Cleome sen·ulata Pursh and C. lutea Hooker) are moderately attractive to N. m. melandm·i, but only for nectar, the long stamens, which bear dark green pollen, being completely ignored. This is the sole genus of plants from which N. m. melandm·i is known to collect only nectar. J_;IFE HISTORY OF ZONITIS ATRIPENNIS FLAVIDA Although Zonitis at1·ipennis fiavida has not been completely reared under laboratory conditions, it has been possible to outline its life history through partial rearing experiments, coupled with numerous observations in the field . As in the case of most other 232 THE WASMANN JOURNAL OF BIOLOGY, VoL. 12, 1954 species of Nemognathinae which have been studied, the winter is passed as a fifth larval instar, enclosed in a capsule formed by the exuviae of the fou rth instar. J_;ATER LARVAL DEVELOPMENT AN D P UPA TION. 'l'he fifth instar (fi gures 6, 11 ) is dark orange in color, moderately depressed and slightly curved in form, and from 10 to 11 millimeters in length. The antennae, mouthparts, and legs are vestigial.