1 INTRODUCTION
The Japanese giant silkworm, Caligula japonica (Moore 1872) (Lepidoptera: Bombycoidea), is generally considered as a forestry pest due to its damage to many trees, particular for walnut tree (Chenet al ., 2021a). It is widely distributed in Asian, and its damage caused huge economic loss every year in Japan, North Korea, Russia, and especially as to China. However, recent research indicated that the cocoon of pupa (Figure 1) displays nontoxicity, biocompatibility, suitable mechanical properties, and porosity while showing no adverse effect in animal trials and even appears to enhance cell proliferation, so it could be used as natural medical mesh in the medical industry (Chen et al. , 2022). While the genetical mechanism of this compatibility are completely unexplored. There are two types of diapause for C. japonica . It overwinters with egg diapause. The egg period lasts until the middle of May of the next year and pupates from the middle of July. The pupal period is about 40 days, which shows summer diapause (Chen et al. , 2021b). Diapause of insects is common, but it is rare for a species to have two diapause modes. At molecular level, the regulation mechanism related to diapause C. japonica have remained unknown. To more in-depth research on regulation of diapause and exert its potential medical value of C. japonica , a high-quality genome is an essential tool.
As a miniature animal group on the earth, insects have evolved a variety of strategies to resist unfit environment to survive, among that diapause is a very effective strategy. The regulation of insect diapause involves many factors, such as the induction of abiotic factors, photoperiod, temperature, and humidity. Both long and short light can induce insects to enter diapause, For instance, Mamestra brassicae will enter summer diapause when the illumination is > 12h (Goto and Hukushima, 1995); Chilo suppressaliswill enter winter diapause when the illumination is less than 12h (Xiaoet al. , 2010). While the regulation of hormones and some foundational proteins are always inseparable as biological factor (Denlinger, 2002). Studies have shown that Ecdysone, juvenile hormone, prothoracic tropic hormone (PTTH) and some rhythm genes,including diapause hormone (DH ), period (per ) , timeless (tim ) , Cryptochrome 1(CRY 1 ), Cryptochrome 2(CRY 2 ), can affect the diapause of insects (Denlinger, 1985). Nevertheless, it is poorly understood how rhythm genes regulate diapause of C. japonica .
The high-quality genome can help to explore the new function of key genes in insect physiological regulation and searching for new metabolic pathways. Here, to better study the diapause mechanism and explore the genetic of C. japonica , we conducted high-throughput sequencing of its genome and obtained high-quality chromosome level genome. The rhythm genes closely related to diapause were annotated manually. We provide a helpful genome sequence resources for in-depth investigations for insect diapause and forward research on C. japonica .